To those wondering about the origin of the myth: Cutting using only the cross-slide instead of the compound set at 30 degrees (with a full 60 degree tip, of course) will cause the cutting action on both sides of the thread profile to make chips that collapse in towards each other on top of the tool as they are formed, which can tangle and jam and chatter. Cutting on one side of the thread OF COURSE will shear off a tiny bit off of the other side equal to the depth of cut, just like any other facing or turning does, but it lets the chips fly free and unhindered. The final light cut at full depth using the cross-slide will cut on both sides to clean up the small amount of stair-stepping you get if the compound is set 1 degree over* 30 (which was preventing you from constantly dragging the whole "unused" edge on your work while hogging the thread). *I originally said 1 degree under 30 leaves steps, which was incorrect.
Correct. The way I explain it to anyone who should ask is. The reason you set the tool at 29 degrees is to reduce the load on the left side of the tool. The tool does in fact cut on the left side but only by that one degree to the depth you just dialed in. You do end up with a stair step but no where near as pronounced as you think.
At compound < 30 degrees, you do NOT have ‘stair stepping’ both sides cut. The thread form tool is set perpendicular to the work piece center line after the compound is set at whatever angle < 30 degrees you like. Not sure where the confusion comes from; but if you just want to use the compound, go for it. But like the POST says, you’re gonna have chips rolling onto themselves. Also, note: not sure where you guy’s are talking about .030 or .060 cut depths and at 250+ rpm ! As professional gunsmith, I’m at 60 rpm, first pass .008” and then less and less depth of cut as it progresses. Using a 14” Monarch very heavy lathe or the Clausing medium size lathe. Also, Joe, love your left to right threading videos; but when work is between centers… you crash if you let carriage continue on while you twiddle your fingers. Hahahaaaa. Thanks Joe, on my gosh we learn SO much from you !
29 degrees, if everything is set up accurately, will NOT produce a "stair step". Anything from 0 degrees to 30 degrees will cause cutting on the right edge of the tool bit with 30 degrees being the case where tool bit and machine flexure would be causing some right hand edge cutting when mathematically (geometrically) there would theoretically be none. However, greater than 30 degrees (or any of the many set up errors people can make) will produce a stair step.
Thanks to those who pointed out my mistake. 29 takes a skim pass on the secondary face leaving a clean finish with minimal loading on that face, and 31 leaves a slight step which would need a final skim pass with a plunge on the cross slide. I've edited my original comment so as to not lead astray future readers.
Realistically the 30 degree feed trick does one thing, it reduces the minimum force required to cut a thread, for a big machine it may not matter, but for a smaller machine, or a less rigid part, it can make a difference.
No it doesn't. Because of backlash the leading face of the tool always does the work. The reason oldtimers say to set your compound @29.5° is for feeding w the compound. This is an old school way of keeping track of your thread and w the wide adoption of the dro is almost never used. There is a reason for everything
@@Rough_cut613 So you think cutting a chevron shaped chip vs a normal chip is the same? some of the cutting force is shaping the chip, think about the forces needed to bend a strip of metal, vs an L shaped piece of metal. the L shaped piece requires much more force to bend.
I don't know if this is still a myth, but I was taught to step using the compound because the cutting tool is more prone to chatter if both sides of the tool are equally loaded. Cutting primarily with the leading edge puts force against the tool holder in the ordinary location and direction.
Joe, firstly let me be clear that I have great respect for your immense skill and experience and I have learned so much from your excellent videos. So, with the greatest respect I think the issue here is that the original 'old school' teaching has been mis- interpreted and mis-quoted by generations of later day armchair experts. The old school technique was to set the compound at 'slightly less' than the thread angle so that the tool cut 'mainly' on one side, inorder to reduce chatter on small, primitive, non rigid, hobby lathes when cutting coarse threads . There was no mention of the tool not cutting at all one side. Somewhere over the passage of time 'slightly less' became the (incorrect) 'rule' that you had to use exactly 29.5 degrees (for a 60 degree thread). From this, it was a small step, to develop the incorrect belief (myth) that the tool didn't cut at all on one side. So, while you are totally correct to debunk the myth about only one side of the tool cutting if the compound is set at 30 degrees I don't think that undermines the value of the offset compound technique for small hobby lathes trying to cut coarse threads, but it's important that newbie lathe operators realise that '29.5 degrees'' isn't 'gospel' , it really means a few degrees less than 30. Regards Paul in NZ
Thank you for your comment. Feeding a threading tool with the compound set at an angle, greatly reduces the tool load and is a huge benefit for a lighter machine or small diameter part. My work and machinery allows me to just feed straight in. I thought debunking the myth may help to clear some fog.
Cutting tool loading is the same regardless of in-feed angle. It is the Depth of Cut that is the primary factor in cutting tool loading. Greater the cutting load on a specific cutting edge will wear that cutting faster.. It is all a trade off. @@joepie221
Here, here!! Or is it There, there? Meaning "there" will always be those who just have to make something simple and straight forward way more complicated than it really is!!
I never heard that the back side of the tool didn't cut but just that you wanted the leading edge to be performing most of the cut and the trailing edge to be performing a minimal cut. This was to keep the leadscrew pushing the tool under a constant pressure through the work. Not sure there's much effect on good material with a constant diameter. All that said I know good machinists who just plunge the tool straight in with acceptable results. I still use a bit less than 30 degrees and the compound since many of my tools have side rake.
That is what I was taught in high school metal shop as well, back when such classes still existed. I guess I just assumed that when people talked about cutting on the leading edge of the tool it was understood that meant _mostly_ on the leading edge. I can't say I've ever had anyone try to tell me the trailing edge didn't cut at all. I guess I don't get out enough.
@@seantap1415 I DID NOT KNOW THIS i have all ways had set at 29 ish with a carbide tip tool would this work using your way of doing a thread or is your tool a ground type
Russ Kepler; That is exactly how I read all the instructions when I taught myself from books and videos from such as our esteemed Mr Pie. The idea, as I understand it, is to reduce chatter caused by both sides cutting equally. It certainly works for me on my 100 year old Drummond 3 1/2" centre (7" swing) lathes - as long as I engage the tumbler reverse the right way to not get left hand threads :-( You might guess that I have to set my compound at 27 1/2 degrees :-)
Is this a myth? I've never thought that anyone was literally saying they right side of the tool doesn't cut even a little tiny bit, just that *most* of the cutting happens on the left
@@Voxters sorry but I have seen it written in a number of places that the RH side of the tool does not cut but Joes demonstration shows that to be false. I only hope you have half of the experience that Joe Pie has mate, if not keep the mouth closed lol
@@samrodian919 Seen it WRITTEN hm? ;) No one said, the backside doesn´t cut. It removes exactly that much material which you move forward with your tool and smoothens the backside. Thats why Joe endet up with Staircases on his "removed backside" Tool. Stop reading silly tweets, grab pen and paper, cut it out and try it yourself.
(Because sometimes, threads are left-handed...) The ratio of cutting by 'front' side of tool vs. 'rear' side of tool is going to depend on feed rates and thread profile's angles. If you could get things set up just right, you could probably get it so the 'front' side does ~99.9% of the cutting, but, you are not going to like the result: as Joe mentions, that surface of the other side of the valley is going to be really crappy & grooved: who wants that? If you are doing some very large batchwork, (depending on materials) it *might* make some sense to do a little trig', and come up with an approximate cutting ratio, to help guide your tool changes/maintenance.
Thank you for validating what I've been thinking recently. When I think about the interface between the tool and the work, there's no difference between using the cross-slide, the compound, or increased stick-out of the tool from the holder (leaving aside the loss of stiffness from this) to achieve the next deeper cut. The geometry stays the same. The work can't see the compound whatsoever, only the tool.
Wow, Joe, great minds think alike; my machine shop instructor went through a very similar tutorial almost 50 years ago; thank you for the memories. I enjoy watching your tips, tricks, and how two’s, thanks for taking the time to share them with us. Play safe from Elliot Lake, Ontario, Canada.
I’m happy you did this video, because I’ve never been able to convince people of this. It seems logical to believe that the tool only cuts in the direction of movement, so that’s why people believe it. But each time the tool is moved in, the rear is also moved in, so it cuts off the rear of the thread. It’s always been obvious to me, which you demonstrated extremely well. When you move the 30 degree tool in, either by using the compound, or the cross slide, you’re moving it in towards the center of the piece. With just 30 degrees, you have to leave a step on the rear of the cut, because there’s no edge to remove the step. No matter how the tool is moved inwards, it’s moved in step by step, which leaves a 90 degree back edge. It don’t understand why that’s hard to realize. Guys, no matter where you go, whether it’s people on UA-cam doing machining videos, some of whom who should know better, or even machining articles, say that moving it in 30 degrees with the compound just cuts on the leading edge, and supposedly is lessening tool pressure in doing so. I’ve read this innumerable times over the more than 50 years since I first started doing this. It’s so ingrained that nobody has ever tried it out publicly, as far as I know, until Joe just did here.
I began my machine shop training in 71 and was taught this fact entirely in the classroom. I've tested it more than once "accidentally" by less than a perfect 60 degree cutting tool. I was taught "threading is always with a form tool", we did have "NC" back then, even as CNC was only beginning to be mainstream in general service machine shops. We were also taught to take one last pass with the cross slide of a thousandth or two to ensure the form of the thread came from the tool form.
I think that using the compound slide for the incremental infeed when threading has many advantages, A: reduces the load on the tool. only 51ish% of the total length of the tool actually engaged with the work, both sides, is really doing the cutting, Drastically reduces chatter B: this allows you to set the cross slide handle to a comfortable position for fast and easy retraction each pass and back to 0 every time, no number to remember real nice for large deep threads!! C: chip control, if all I ever did was brass not only would I be a happy camper and none of this would matter, BUT straight in feed large diameter internal threading in 304/316 stainless makes the shittiest chips you can imagine.......
i use crossfeed only for fine threads, compound for coarse threads. At what pitch do I change techniques? It depends on the material, the machine, the insert...other factors that I can't think of right now...
GASP Joe! you threaded towards the chuck!!! Nice demonstration, Pierre taught me to thread straight in plunge cutting and it has not failed me yet. the only time i have used the compound is to pick up an existing thread.
Great demonstration of thread cutting using a compound angle tool vs a leading angle tool cut only... I suspect the trailing angle of the cutting tool is also stabilizing the torsional vibration being generated, when using only the leading angle of a cutting tool .
he said that in the video @ 14:26. Point is you still need both sides, doesn’t matter how much on the right side is needed, it’s a fact that right side is needed.
The back edge provides a wiper action on infeed. If infeed was some small fraction of the tip radius the finish would be great, like the V groove you cut with it.
Set top slide at 90 to cross slide, use cross slide as accurate depth of cut (no guessing) and on each pass move the top slide towards the left 50% of depth, (right hand thread). (can vary from 50 to 80% depending on material & tool type). As an apprentice i was taught this & have been doing this for 50 years with out a problem. This takes the excess force of the back face, It has no chatter, the finish is perfect and the depth is very easy and much quicker
Yes! The 29.5°/30° on the compound is meant to help reduce tool contact and chatter. PS Alternating flanking or ziz-zag threading on a cnc is awesomeness.
Indeed, the other side of the tool would need to be a minimum length of whatever your feed on the compound is. Love your technique of measuring thread depth btw. Been using it for a while now and it's super helpful, thanks! 😊
The idea isn't that the tool doesn't cut on the backside. It's that the bulk of the cutting is done on the leading edge and all the back of the tool does is basically spring cut what is missed. That's why I never use the compound to cut fine threads....it's just not necessary. Now start cutting 4 tpi in 4140 ht and yeag compound all day long. The tool still cuts on both sides just not nearly as much when the compound is used. I run big machines and straight in works perfectly fine for most alll threads
In my experience you have to have a really beefy lathe to get good results with direct feed, otherwise I use the 29.5 deg angle. I always do a spring pass at the end too- I do this by manually pulling back on the tool post without moving the handwheel. You usually get a few tenths play away from thread contact this way, and you can reverse the cut with tool still at depth- but hold back as it passes the thread- then let go when you get back to start, and re-engage the leadscrew to cut. The effect of this will be removing an extremely fine amount of material for the spring pass, cleaning up the thread nicely. Direct in works well too I noticed if hard turning threads on hardened materials, like Bearcat 44 drill rod, or Viscount 44- using the compound on a Harrison 500, it would just spring against the cut. Sometimes a direct in cut works best, but I prefer 29.5 deg.
I have run large threads with part of the thread tool relived to help with chatter but you have to leave the nose of it in tacked. I've cut some extremely large threads (like 1/2 TPI) on some relatively small lathes with just a narrow grooving tool with only the v formed on the end. You just have to run the tool up and down both flanks of the thread, takes a while on a manual lathe but works.
Yes, I agree. I used the same technique to cut threads up to 5 mm / 5 TPI an my small Emco C 8 lathe. It takes ages but you can cut really large threads this way. @Joe I love your clear and instructive videos - always a joy to watch.
I’m mostly a mechanic, but yesterday I needed to lengthen the threads on a bolt to make a jack screw to pull out some flanged bushings. Anyway, I set the compound to 29.5°, or 59.5° on this lathe, like I was taught in school. Then I needed to square the tool, but I couldn’t do it against the face of the chuck because the tool had a weird offset, so I asked one of the machinists if he had a fishtail gauge. He didn’t know what I was talking about… but he just lined up the tool in the existing threads. I felt dumb. But he also asked me why I had moved the compound. He said he always cut threads by feeding directly with the cross slide. He said it’s a carbide insert and the lathe is strong, just go for it. And indeed I cut the best looking threads I think I ever made. The irony is that I learn to cut threads in school using the same exact carbide inserts, but I guess the teacher wanted us to learn the hard way… Or maybe he didn’t even think about it. The HSS tools were just cut from the program 3 months before I started. Still, the machinist was surprised that I knew how to cut threads, especially metric threads, and that I knew my way around a lathe. I pointed out that I know every machine in the shop literally inside and out because he breaks them and I repair them… haha.
That's neat that you have all this and the thought put into it, the time spent, and learned more by doing. I change bushings like you describe with a c-frame and forcing screw. The ends are selective for different size bushings. The biggest lesson when being paid only book time labor for a technician, other than a trick that's super fast, is using the right tools to begin the job and be done with it on time. At your leisure, on your own car, you can reinvent the wheel while you're at it. Nowadays you can use a tool and return it quite often at the parts store or get it cheap at Hebrew freight.
@@dannylinc6247 In this case the bushings were already tapped for the use of jack screws, but we didn't have M16 allthread on hand. I say mechanic but I'm a millwright in a fab shop. My team does all the shop maintenance, in addition to repairs and modification on all kind of customers equipment of all sizes. My speciality is mostly electric controls and hydraulics, but I'm an OK welder and machinist. 90% of the time when we need a tool, we make it in the shop. Also we're in a pretty small town, way north of all the big cities. If we need something it's not next day shipping but next week shipping. And with Covid it's next month shipping now.
Agree completely, I was taught the 29.5 deg method long ago, but I plunge everything nowadays. For me results are the same or better in difficult materials as well. Perhaps it has to do with modern carbide tooling. Carbide does not like rubbing, in my mind a properly rounded 60 degree tool should actually perform better plunging since depth of cut will be more consistent around the tool. I can speculate that perhaps sharp HSS tooling and less rigid lathes may perform better the old way.
Joe, again great content! I sure wish my dad was still with us, he was a humble self taught machinist and like you was a genious. I used to send him ytube vids on discs and would have sent him yours as well. Many things I'm certain he would have said "Ya, ya, that's how you do it" yet on other things he'd say "Oh, that's a good way to do it!" I've learned much from him and learn much from you. Thank you for your knowledge, experience and humble way of teaching, that is what keeps many of us coming back for more. God bless.
I've never heard that said. The reason for setting up at an angle is to reduce the load on the tool and work. It does cut a little on the back, but nowhere near as much as if you plunge straight in. When you're cutting a long coarse thread on a difficult material, you don't want the job climbing up over the tool. It also makes it more convenient on manual machines, using the cross slide to come back to zero. See how inconvenient it is, plunging straight into the work, having to keep track of the depth of cut each time.
@ Roger Froud- your explanation is exactly what I was taught by the old machinist teacher that taught me over a decade ago. I was never told by him that the rear of the tool didn't cut- he had me set compound at 29.5- it didn't rub as much, just as you said. You absolutely do need the rear of the tool angle- Joe's totally right on that- I have no idea who the hell came up with this idea that the rear of the tool doesnt cut. Of course it does! Joe's right about not worrying about your depth of cut- I couldn't care less about that- you just cut the major OD for external threads, or minor for ID ones, and cut until the thread fully forms to it- the last little bit is usually hand fit or thread wires or thread mic anyway
I heard of that but chalked it up to the left side taking the brunt of the forces allowing the right side to maintain at least some contact with the work.
The question is really one of tool pressure and direction. During normal left to right turning the lead screw is driving the carriage towards the chuck. Cutting forces are maintaining constant pressure forcing the carriage against the lead screw (to the right) and the spindle against the tapered bearing or a thrust bearing if plain spindle bearings (force to left). Atlas lathes like the one I have are designed around these forces. The lead screw will be forced to the right as the carriage is forced left and so Atlas made the pillow block support on the right end of the shaft deliberately weaker so it will protect the lathe. The right side of the tool will cut during threading but I like to keep it to a minimum. If the tool pressures on the right and left cancel each other the carriage COULD drift. If the tool pressure on the right side somehow exceeds the left pressure then the carriage may jump as the slack comes out. Bottom line if you have a nice tight machine plunge in at 90 degrees, if you have a lot of play like my old machine you got to deal with it.
I've always used a 60 degree tool sharpened at about 50 degrees, with a full radius on the point. Because of the radius, which cuts on the back side, I have never detected any stepping at all. Every thread that I've ever seen has a radius at the bottom--a Sharp corner creates a stress concentration which encourages breakage.
With the speed you are running and pulling out of the groove and moving back to the beginning of the cut with the lathe still running, how do you get the cut indexed in the correct position? Decades ago, and older machinist showed me a threading procedure as thus: He ran the lathe very slow, made a forward cutting pass, and stopped the lathe. Then without disengaging the carriage backed the cutting tool out a few thousands and reversed the lathe to get back to the beginning of the cut. Stop the lathe, still without disengaging the carriage. Then set the tool for the next cutting pass and go forward. Note that the carriage is never disengaged so that the tool is always indexed to the groove being cut.
@@EpicZombiez2314 I learned to thread using the dial, slowed me down a bit when I moved to a different shop where none of the machines had a functioning or present dial. At least now I can do it both ways.
I've just sketched out the path the single point takes with the compound slide set at 30 degrees and it shows a small triangular section that is cleaned up at each new pass of the cutting tool. This clearly shows that a full 60 degree tool is needed to form the thread but only a small section of the back edge of the thread equivalent to the depth of cut is removed from the back edge at each pass. The sketch also clearly demonstrates the ragged side of the cut as demonstrated in the video if only half a tool is used.
In theory the only part of the right side you need is equal to the amount of infeed, the size of one of those steps. The entire rest of the right hand edge is superfluous.
On a side note in cnc canned cycles for threading in several of the cases i have come across the tool path as far as the feed is concerned can be controlled as a right, left, or both sides with each pass. Left the right then left and right descending offset as to put a larger or smaller per chip load on the sides of the tool. Including a straight down feed as well perpendicular fo travel. In all things manual this is a user subjective approach and confidence. Final pass should always be both sides more or less and always with a full form tool. Joe you nailed it on this video. The fancy stuff is simply for tool life management and chatter control. I think Kimber commented his lack of a compound,. He may have less chatter than a 29deg angle with a compound in overall ridigity. The comment about chatter in plastics is all reduced to tool material and rpm. Super honed tooling is best for plastics with high positive geometry and a chip pocket, imagine a knife blade reaching up into the part.
My first attempt at cutting a thread produced the ugliest screw you can imagine but the nut didn't seem to mind so I used it anyway rather than spending another 5 hours trying again. Changing the gears on a mini lathe is a job in itself.
There is a very important distinction to be made here: the 30* compound setting is relative to the cross slide axis. I.e., it is the angle off of perpendicular to the spindle axis. If you're thinking "Duh, what else could it be?", on some lathes the compound angle is relative to the spindle axis. I.e., 0* is parallel to the spindle axis, not the cross slide axis. On these lathes the compound is to set to 60* for threading!! It's the same position in both cases, it's just the reading on the scale that's different.
I see the 60 degree thread profile as a flashlight beam in a dark room. You set your compound within the light and off ya go. Whether the index mark says 30 or 60, you have to be in that beam.
I have never used the compound slide offset from zero when cutting threads, so I've never even considered it possible to form anything that would resemble a 55 or 60° thread with a half form tool? I've only ever used the cross slide for depth increments, a full form thread cutting tool, and the chasing dial to synchronize. Then I test fit the mating part wherever possible before removing the finished part from the chuck. The form and fits come out perfect every time👍🇦🇺
Same here with with 55 years machining experience apprenticed in a shipyard, never turned the compound slide for screw cutting and always worked fine:-))
@@johnhili8664 Yeh, and by using the compound slide set on an angle to make depth adjustments, wouldn't that screw with correct thread engagement when using the chasing dial?
@@simonilett998 That's another thing I never use chasing dial as even those can make mistakes especially on fine threads!! I always reverse the lathe, for my hobby stationary engine collecting I have a Myford Super 7 and a Colchester Mastiff!!
@@johnhili8664 Yes, I think the chasing dial is only good for coarse imperial threads from memory, and you don't want to move the carriage when using it or it could throw off the position. I was taught the same, pretty sure from memory I leave the lead screw lever engaged, drop the feed into neutral and back out the cutter after each pass, then switch the feed to reverse to keep everything tracking the same, and it takes any backlash etc into account too.
@@simonilett998 I think it does not affect the timing but still I cannot tell as I have never used it in my 55 years experience:-)) Here have a look at some of my steam engines ua-cam.com/video/iyvqs5Fb4Oo/v-deo.html
In Australia we don’t set the compound to half the thread angle but advance the compound slide a small amount to reduce the cutting on the left hand side of the tool. This reduces tearing and improves the finish. I used a ratio of 1:5 which worked for me. This is what is needed with hand ground high speed steel tooling with no side or back rake. With introduction of carbide insert tooling with magical tip geometry I think the need for advancing the tool is not needed anymore.
My Sherline actually does threading fine using only the cross slide. Of course, it doesn't come with a compound. I've never done coarser than 1/4-20 though.
I also have a Sherline, (and love it) but I have done threading on larger machines and as good as a Sherline is it, it can not make nearly as deep of passes in threads. That is the difference.
Joe, you failed to mention the reason why using the compound for thread cutting is the industry standard: it's all about reducing tool pressure. Your demonstration on an extremely soft material like brass is kind of ridiculous. Using a harder material, like 4140PH or 304, and doing a direct comparison using the same form tool, with identical rpm's and feed rates, would have demonstrated that the compound method produces smother threads. That's why it is the industry standard method.
@@MF175mp Using the compound for threading was the standard LONG before the internet or computers even existed. Real world machinist typically keep the compound set at 29½° and it doesn't take us any longer to cut threads doing it correctly. Using just the cross-slide for feeding is a lazy method, not a good method, and Joe is doing a disservice to his audience by promoting a bad technique.
so as a guy that runs a cnc on the daily. I can tell you this will work perfectly and has the advantage of reducing chatter if you clearance one side of the tool. (staggered cut can be even better) if your tool has a 0.004" radius at the tip, you want your compound in feed to be about 0.001" per side for a decent finish. definitely not a fast way of doing it, but it will save your but sometimes.
Excellent clear demonstration of what is actually occurring during a single point threading operation. It is my understanding that the oblique approach was to reduce chatter by using the leading edge to remove more that the trailing edge. Thanks for sharing, best regards from the UK.
Being something of a single point thread cutting fan i have heard the hard of thinking say how you have to set the top slide at half the angle. Well never taking advice without confirmation i experimented cutting some stainless with a full form insert both angled and straight in and looked at the results under a microscope and you couldn't tell the difference. What is the problem if the tool does cut on both sides? Is your lathe made of cast iron or licorice. The top slide is more useful left at the correct angle, in line with the lathe axis and marked zero on the degree mark.
Joe, could you do a video on the idea of tilting a threading tool to the thread helix angle, and explain how that does or doesnt work? I always thought if you did that one side being lower than centerline would smash, and the other being higher it would rub and not cut, but supposedly it's an advanced technique some would use, and I've always been curious how that actually worked or didn't work at the cutting surface. In fact it's one of the few things about cutting geometry that still confuse me when I can understand some otherwise very complex tooling. Can you cover that sometime?
This practice of cutting threads via feeding the compound set at 29.5/30 degrees appears to be a very American tradition that was practiced nee 100 years ago when lathes and thread cutting tools were very different than they are today. Back then majority of cutting tools were high speed steel and often cutting edges were ground by hand. Due to the tolerances/precision/accuracy required for proper threaded parts to function, it might be possible to compensate for cutting tool dimension issues. SO much has changed with threading tools since then, Same applies to engine lathes made today. Yet, these century old American machinist traditions persist in the very different machine tool world of today. Looking at how single point lathe threading is done in Japan, EU and other parts of the world, thread feed is done direct in using the cross slide.. this feeding via the compound set to 29.5/30 is virtually unknown. Personally, learned how to thread about four decades ago from a master machinist in a tech company model shop on a Hardinge HLV-H, no feed via the 29.5/30 degree compound, thread cutting feed was direct on with the cross slide using a carbide insert threading tool. Start threads with modest cuts, maybe 0.01" with progressive smaller cuts as the thread depth increase to about 0.002" per cut or less to achieve the required thread dimensions. To this day, cutting threads are direct in feed using the cross slide.. Regardless of thread pitch or thread form.. Proper Selection of threading insert, feeds, spindle speeds and all for the material being worked on can and does make all the difference in finish and results. Fact is, threading is a form tool operation no different than cutting a groove, part off or similar. As for chip formation and clearance it has much to do with cutting tool geometry. Today, carbide threading inserts can easily achieve levels o accuracy/precision/tolerances and cutting geometry not possible in decades past. Add to this carbide and coatings used on high quality modern threading insert completely alters how thread cutting tools function in every way imaginable. Consider how ACME, Buttress and many other non-triangle thread forms are made.. With the majority of these non-triangular thread forms, this "business" of feeding with the compound at some is absolutely not done. As for chatter and poor thread cutting results, that is more to do with cutting tool and set up rigidity, stability, feeds and cutting surface speeds related to what the material being worked on requires. As for threading away from the chuck, there is about zero reasons to NOT thread this way.. Unless the lathe has a right hand threaded on chuck. For lathes with RH threaded on chucks, any operation with the spindle running CCW greatly risk unscrewing the chuck.. resulting in a near instant disaster.
There might be a little baloney in that long winded explanation...single point threading has barely changed in the last century. Feeding at 29.5 allows the leading edge to bear the main cutting force, so chatter and vibration are absolutely reduced. It's only for roughing, as you want both edges engaged for the finish cut. If it's not needed or used in most of the world, why does my Japanese CNC lathe infeed at 29.5 degrees??? Maybe because it works!
@@peoplepower1272 Fact is the edge moving in the direction of cut does the cutting, once the DOC has been set regardless of how it was set (angle indeed-via compound or etc) or radial infeed via compound or etc.. This act of metal removal is not static, it is dynamic and due to the fact the metal bits involved (cutting tool and work being threaded) are moving changes the perception vastly. This angle compound infeed belief/idea comes from the reality threading tools were hand ground nee 100 years ago. Since then modern threading tools have vastly changed far beyond hand ground high speed steel cutting tools and carbide insert geometry. Ponder how many production cnc machines today use hand ground high speed threading tools...? Here is a chart from Mitsubishi, carbide threading insert manufacture.. Direct radial infeed is recommended with their threading inserts. Not just radial infeed, the depth of cut per pass is also recommended. Why is this, modern carbide threading inserts have chip formation geometry moulded/ground into the insert that negates any need for this angle infeed for threading. Bottom line, believe threading cutting beliefs/ideas from nearly 100 years ago that was based on cutting tools and machines that are of that same age or accept the fact science and technology has moved far on from those ideas/beliefs.. www.mitsubishicarbide.net/contents/mhg/de/html/product/product_guide/information/turning/threding_ex_03wit55.html BTW, there are full form threading inserts that cannot be used with angled infeed... As for cnc lathes, virtually any type of cutter infeed can be programmed as needed and this does not apply to any specific Nationality of cnc machine.
Joe, You are absolutely right Again !!! Thanks a bunch ! Joe , you are always there to help those of us who need to learn at home and on the job. Paul Kerst Glen Rock PA.
I was taught to single point by several old timers and this is the first time I've heard this nonsense. We keep our compounds set at 30 all the time, when I asked why, they said it was so you could "pick up" an existing thread and fix it. I've been cutting single point threads for over 20 years in a production shop, both with and without a compound. If you have ever actually WATCHED the tool cut, you can easily see it's cutting on both sides.
I'd bet it's an idea spread by folks that have only been trained on regular lathe work, and never used their brain enough to ask if it makes sense for threading. If you let them do something they're not actually trained on, they'll probably break tools.
@@taxicamel 25 years in a PRODUCTION shop and you come along and claim I don't know where I work, that's hilarious. "You DO NOT "pick up" any threads in a "production" shop situation." You ever heard of REWORK or CUSTOMER REPAIRS? You don't send PRODUCTION parts to MAINTENANCE to have them reworked. Have you EVER working in a machine shop or did you just read the WIKI article on single point threading? The ORIGINAL argument the video was covering what the idea that a single point threading tool ONLY cuts in the leading edge. This isn't true, and even YOU said it isn't true, but you're like 'well, yes it does cut on both side, BUT it cuts MORE on the leading edge' SO? it is STILL cutting on both sides, just like I OBSERVED. ALSO, I have single point threads on THOUSANDS of parts on machines WITHOUT a compound, and in those cases the threading tool DEFINETLY cuts on both sides. As for if I would listen to someone, sure I'm always willing to learn, but that someone would need to know what they are talking about, which leaves YOU out.
I don’t understand something here with the 29 degree thing. Is the tool set with the center line at 90 degrees to the work with the compound at 29 degrees? Or is it set at 90 degrees to the work with the compound at 30 degrees then the compound is moved to 29? If the tool is 90 degrees to the work then you will get the profile of the tool as you are threading regardless of the compound. If the compound is moved after squaring the tool then you are not cutting a 60 degree thread. It seems like the 29 degree thing is meant to compensate for deflection while moving sideways while cutting resulting in an accurate profile. With a rigid setup it doesn’t seem to be necessary.
You're not going to like the answer but.....it depends. American (and I believe UK) lathes reference 0° from perpendicular to the work and import (Chinese specifically) reference 0° from parallel to the work. Essentially the idea though is to advance the tool with the compound (aka top slide) at 30°, the same angle as the flank of the thread so you're only cutting with one side of the tool and hence not pushing it as hard as when you just plunge straight in. Joe's clearly debunked this simplification of the process but on smaller lathes, the idea is to reduce the tool pressure to something it can handle. Why 29.5°? It doesn't matter if you're at less than 30° (I'm assuming a 60° threadform here but otherwise half of it), the right side of the tool would just cut more ... but you cannot be over 30° so 29 or 29.5° just err on the side of caution.... because if you're on an import lathe like mine, when it says 30° (or rather 60° on an import!>, that could be 29, 30 or 31....on a good day! Incidentally, Joe's got good videos of how to set your compound accurately for when it does matter.
I’m lazy - I just plunge in on the cross slide - can’t be bothered moving the compound . I also find that not having to trig out the feed for the compound easier . With the compound set to half the thread angle it still cuts on the trailing side but the bulk of the cut is on the leading side which can help to stop chatter or a dig in on light machines , you also have to be careful threading up to a shoulder or in a blind hole as having the compound set to half the thread angle not only feeds the tool in towards the centre axis but longitudinally so the little bit of clearance you had at the start can disappear and you end up driving the tool into the shoulder or bottom of the hole . Threading away from the chuck fixes that problem ! Thanks for the fantastic video Joe , I know this has been picked up on one of the model engineering forums and I look forward to the ensuing squabble it will cause 🤣
The biggest advantage of the compound slide set over at the angle is when you are threading the end that needs tailstock support. Then the angled compound gives more room with some machines. On other large machines it won't make any difference which way the thread is cut. A lot of cnc machines will use a zig zag approach, where the left hand side of the tool is used first, and the 2nd pass it will use the rh side of the tool second, etc and finally uses a plunge cut to clean up both sides at the last cut.
Enjoyed the video and reading most of the comments/replies….I book learned compound, never attempted a change as it works even though years ago I understood that plunge cuts also produces the same thread….time for me to modify my methods….tks
Hi Joe, as a retired toolmaker I find your videos of a high caliber and informative for many wannabe engineers . As far as threading is concerned I thought all my Christmases came together when I got hold of full profile carbide inserts ( many moons ago ) from a reputable brand . I soon found out how accurate these inserts were by comparing the effective size with the OD and found that working to a tolerance you didn’t need to measure with those horrible screw thread micrometers and could solely rely measuring the diameter ( crests ) with a standard micrometer and as a bonus no burrs . I am sure you would be aware of this . Happy screw cutting !
Most of the time I ignore the compound for threading, simply because it's rarely on the machine anyway. Heck, I just cut a M42x2 thread in cast iron at 650 rpm, 'cuz that's as slow as my beast goes, with minimal issues, except the terror of a possible crash.
Your right it dose cut the right side as well how ever by doing this that cutting length is minimal being only the length of your tool move. The means your only cutting load is still only 55% percent verses a full cut all across both sides of the cutter meaning 100% cutting load.
Could you do a follow-up on cutting the thread only on the cross slide, vs with the compound at 29.5, 30 and 30.5 degrees to see if there is a difference in chatter marks and on which face(s) they occur? Maybe it has to be in a harder material?
I'm pretty sure in his other videos he's stated that he never uses the compound to cut threads, always feeds straight in with the cross slide. So pretty much any of his videos where he threads will be with the straight in method.
29.5° will shave a slight amount off the right side with each pass, 30° will shave none off the right side with each pass except for the DOC at the tip of the tool and 30.5° will blow the thread profile! :-)
I have no idea why anyone would imagine that the 'back' of the tool is just there for decoration ;-) Even a simple electronics guy can see that threading is a 'form tool' operation ...ah, well, myths have to come from somewhere, always fine to see another video from you, sir, even a 'myth buster' ?
If the leading edge is the only thing cutting. Why, when you buy one of the tungsten insert threading tools, do they come with both sides of the profile formed? I never understood where this, one side doing all the cutting, came from. Leave it to "Joe Pi" to throw another misconception in the wood chipper.
On a manual lathe , the leadscrew always has slack in it. The only time I use the compound is to cut a multi-lead thread. My passes are .010 deep to the last .005, then .002. All straight in from the cross slide. I let most of my passes float with the leadscrew, Then let my palm rest on the apron handle to pull backlash out of the leadscrew. This switches the tool pressure from the left side of the thread profile to the right side. The last couple of thousands has a lot less tool pressure equally distributed around the entire profile. My success rate is 99.9%. If there's chatter, it usually comes from other issues with the machine or the setup.
I apply hand pressure drag to the top of my handwheel while threading 100% of the time. A very worn half nut or leadscrew can ruin a thread if you let it float. I believe the condition is called 'Drunk" and a single light pass is not guaranteed to clean it up.
@@joepie221 I couldn't agree with you more. I believe the idea of setting the compound at 60 was in the days of HSS. Each machine has its own character as you know, but I still enjoy the manuals over a CNC. Maybe its just a control thing. LOL
I always thread with the compound at zero: first day of apprenticeship I was told to do this. CNC lathes don’t have compounds and they make fantastic threads. I was lucky to run a Hardinge clone during my apprenticeship, I miss her dearly.
I paused the video at the beginning to make a statement of fact. The compound is set @ 29.5 degrees so that the tool is whiping clean the back side of the tread, so when you advance the compound it keeps the following side of the tool in contact the following side of a 60° thread that is.
I was taught that the leading edge cuts, the trailing edge guides and cleans the cut. It's a self-piloting mechanism, sort of like a 'gun-drill'. The lead-screw is drawing the carriage ever closer to the chuck, at the same time, the trailing edge of the tool is being guided forward by the screw-threads that have just been cut! The grind of the tool is critical: the leading edge has a slightly steeper angle of attack than the trailing edge. Slightly hollow-grind the top face of the tool, center the 'dip' near the trailing edge. This puts the leading lip slightly higher and steeper than the trailing. Yeah, both side of the tool are needed, but they are doing different jobs!
The tool is advancing into the material. It is impossible for the tool not to cut on its entire DOC profile. The bias of that cut will be determined by the angle of approach. BOTH sides cut.
Think about it, when you screw cut the correct way, it's the cross slide you dial in for each new depth of cut. With the cutting tool set up correctly at 90 degrees from the work piece going through the centre of the angled tip for a standard tooth profile, both cutting edges dial in the exact same amount, and therefore both cutting edges remove the same amount of material. This whole idea of using only one tool cutting edge to cut a thread is counter productive. Me, I started my engineering apprenticeship in September 1976 for Philips Industries in their Research and Development department as an instrument/tool maker.
When the compound is set at 29.5, the main chip flow is facilitated since coming off only one side of the cut while the tool is well supported by the 0.5 on the other side preventing chatter. The 29.5 setup also keeps pressure against the lead screw backlash as does conventional milling versus climb milling.
If all clearances on the hss tool are correct for brass, front + pitch angle + profile and rake(perpendicular to axis), the finnished profile on work will be same as tool. Slower speed with cutting oil helps as tooling point small. I was taught set compound slide half of thread angle and also cut first leading edge then adjust slide to cut trailing edge. The 45° for buttress threads. Cheers
Yeah even if you push the tool into the work at 30 degrees, when you start the movement to make a thread it doesn’t do that. So it should need both sides
Whenever anybody says that the 29 degree setting produces a "stair step", the real reason is that that the compound is not accurately set to 29 degrees AND/OR the tool bit is not ground to 60 degrees accurately AND/OR the tool bit is not mounted straight. With everything correct, the right edge of the tool must cut a little. Assuming you could have everything perfect and chose a 30 degree compound angle, I would still expect a little cutting on the right edge just because the tool will be flexed slightly to the right due to the pressure on its left edge even in a very rigid lathe set up. The reason for the 29 degree (or 29.5 degree by some) is to control chip production. If you cut straight in, a chip curls up and to the right from the tool bit's left cutting edge - and - a chip curls up and to the left from the tool bit's right cutting edge.. These two chips are trying to go into the same air space above the tool tip. Since that is impossible, they collide and cause stress, possible tearing of the metal, and more force on the tool tip. With free machining metals like brass, this might be less of an issue. With harder materials, it can be a huge issue. In any case, you can end up with tearing of the metal at the tool bit tip. Being a little under 30 degrees insures that at least a small amount of cutting deliberately occurs on the tool bit's right cutting edge for not only a good finish but for good contact for heat transfer. Hobbyists may not notice some of these problems as much as they often are making smaller parts with a low horsepower machine and often very light cuts. But in a production environment it can be very important.
That's a good demo Joe! I was taught to use the compound to rough out the thread and leave a thou or 2 for a cross-slide pass to "back-face" the thread and remove the steps. I almost always run a spring-pass as the last cleanup pass.
Having cut threads for the last 50 years, I quit feeding in with the compound more than 20 years ago. I still set the compound on 29.5 or 30 degrees for clearance and to pick up threads.
In the 1980s, I had an order for stock sling swivels and I had to make them with wood screw threads. Wood screw threads are tapered near the insertion end of the thread. I made these by two methods; form tool and form ground grinding wheels. I must say that I have never heard of this myth of half of a threading tool. It did as I expected; created steps on the trailing edge of the thread form. In finishing, my wood thread could not have been accomplished with half of the form and since I had to cut the threads on a taper half a thread form would have looked really bad. This was a very nice demonstration of a weird myth that has come into the machining business. Keep up the "Myth Busting" and I will await your next demonstration.
Thanks for disabusing me of yet another falicy. And thanks for your usual thorough, clear explanation aided by lots of examples. For what it's worth, I'm pretty sure I picked up this one in a night class I took while I was in high school about 50 years ago. While there are those who might say that understanding this process doesn't have any real affect on the final outcome, my experience has taught me that acquiring a deeper understanding of any process generally pays off somewhere down the road.
From a practicality standpoint, it would be good to explain how to go about re engaging a new tool after a disaster of breaking the tip off the first tool. I have a way I use, but it would be good to show how you would approach it. Thanks!
I have been looking at miniature lay down inserts (Dorian for example) and they make UN 60 deg full profile inserts but they always specify them as single TPI. It seems like I should be able to use that cutter for any thread pitch that is higher than the one specified. What am I missing? Are they not dead sharp? great channel, it's nice how many other good channels refer to your work. greg
The term full profile is the key. When the root and PD fall into place, the crest of the thread also forms. You can use the insert for different threads, but it probably won't top the thread profile. You can use the 16 TPI insert for a bunch of different Od threads of the same pitch.
I love this video ! I was taught to set the compound at 30 degrees, I never really thought about it. Early in my career I learned to cut double lead acme threads with no relief cut allowed. You had to time backing the tool out while cutting threads at slow rpm. I don't think i could do that these days.
Joe, great explanation and demonstration. I always wondered about how much the back side of the tool played a part in the thread formation in a single point operation. Seeing the result makes it as you demonstrated, makes it perfectly clear. Based on this demonstration, you don’t even have to set the compound on 29.5 degrees, because it only lightens the load slightly on the backside. It does not completely eliminate it, so it may improve the finish quality but does little to nothing in forming the thread. Thank you
There is a numbered thread gauge dial that runs on the feed rod that tells you when to engauge the feed. I’ve used one since 1974, still a rookie, that’s why I watch Joe he’s the expert and I learn from every video.
@@jamesschrum8924 we just got a lathe and an end mill at the plant where I have been an industrial mechanic for 35 years and I want to learn how to use them.
You're on the right channel. feel free to ask questions. As for your specific question....assuming the machine is set and geared correctly...a solid rule of thumb is to leave the halfnut engaged at all times for a metric thread and control the carriage movement with the spindle direction, for an even thread you can use any line on the dial, and for an odd thread, use only the numbered lines. When in doubt on an imperial thread, always use the same line, numbered or not.
You can set it greater than 30° or less than 30° depending on which way you want the chips to curl - in the feed direction or away from it. Useful if theading ALL the way to a shoulder to keep from trapping chips between the tool and shoulder.
Joe, I am a 70 YO who has minimal experience with lathes/mills (my career has been radar, computers, high tech electronics in general) but even without lots of hands on experience I can see that statement is foolishness. It's about the same as saying you can cut off the bottom half of the 60 cycle AC and still have your negative voltage.
@@peterfitzpatrick7032 : It really is analagous, even to the extent of there being odd quirks that might still generate just enough negative that someone claims they were right after all (a negative voltage can be generated because one of the junctions of a transistor acting as an LED, causing the other junction to act as a solar cell- lousy amperage, but just enough to lead the unaware on wild goose chases...).
dam fine demo there if you were watching it you can see the tool cutting on both sides doing it the proper way with the half ground tool you could see clearly it not cutting on the back side just a question i use a carbide threading tool insert can you cut a thread with out setting at 29* i don't use the lathe much for threading
General Discussion: Of course there are several ways to cut a thread on a lathe. Many machinists will do the whole process without using the compound slide at all. (The Index wheel is there for a reason.) With this method (someone else) saying you don't need "the whole" half of the tool - is a little strange, you may not need the WHOLE of the right hand flank for thread cutting - not plunging, but you will definitely need that portion of the "right hand flank" which is making the depth of cut. (make a drawing and see that parts of the tip are "working" - you need those) A tip ground like that demonstrated also has no support - yes it is very bad.... Another way for fun - would be to blue the tool and make a threading pass to show how much of the right flank cuts in normal thread cutting (using the compound slide).
When a machining channel host presents the statement" Only the left side of the tool does the cutting" it very clearly states the right side of the tool isn't doing anything, and therefore not needed. The half tool used in this demonstration is being used just to prove the right side is absolutely needed. Its the WHOLE point of this video. I personally never use a compound and most of my subscribers know that.
@@joepie221 : Of course when claiming "a thing" in video format it would also be great to demonstrate "said feature" - which you have in this fine demonstration, thank you so much.
When I got my lathe, I did the traditional 29+- compound method. After I saw Joe's video on inside-out/upside-down, I experimented in different metals, DOCs, feeds etc. Conclusion, Joe's method is faster, easier, and gives excellent results.
No myths busted here. The reason behind setting the compound that way is to minimize the cutting load, so most of the load goes on the leading edge which will reduce chatter. That's also why you don't set the compound to 30 degrees, you want it slightly less so it does take a very small cut on the back edge.
Yea i thought 59° was the std so 29.5° would be ideal.. but unless your wanting to cut threads on a fastener thats going to be torqued to yield or if its for a worm gear or something critical of its cut than if she threads than the nut will finish the cutting.. lol..
Regardless of the compound setting, the tool always cuts on the back edge. Maybe not as much as the leading edge, but it does. So for anyone that thinks it doesn't, that myth was perfectly busted.
@@Z-Ack standard metric is always 60 degrees. The point of a thread is that both the screw/bolt/whatever has exactly the same tooth angle as the thread in the nut/housing/whatever. Threads work by locking together from maximum tooth to tooth contact. Just like how a morse taper works.
As for chatter, you either have the incorrect cutting edge angle for the material, or you're not centred correctly. Or, on the other hand, you have bearings that need changing in your headstock, or too much slop between a carriage and it's slides.
Straight in is the British way of cutting threads. I was trained to cut threads at the 29 degree compound slope, and I found it tends to give more angle on one side than the other.. I use a mix of compound and crossfeed. Last two cuts straight in. I suspect that the spiral/helix and tool bit geometry actually suck the tool ahead causing a flatter slope on the trailing edge. The trailing edge of the tool bit may not cut per se but it does scrape and clean up the thread. An interesting experiment would be feed the compound it at say 1 degree to the right opposite of what we normally do and see what happens.
@@johns5447 And I have done the 28-1/2 because tghat is the way I was taught. ,,,,can some body get a sleever or big spud wrnch and help me get my foot out of my mouth. - Iv'e always extracted my foot that way. too so it must be the right way. ;).
But an interesting idea-- use your setup for this demonstration to thread both bolts AND nuts. Then have people try to put a standard nut on your custom bolt, a standard bolt into your custom nut.
Interesting demo. I think the rationale behind advancing the tool with the compound and the notion that the left edge of the tool is doing all the cutting harks back to the bad old days before insert tooling. Older, hand ground HSS tools were mostly equipped with side rake so the left edge was configured for optimal cutting angles on steel and similar ferrous stock. The right edge will cut but not as well as the left. However your demo clarifies the stepped nature of the cut as it advances. I think most machinists understand this intuitively but probably never see it played out this way.
I'm going to put my 2 cents worth in there...grind the cutter to fit the "V" groove on the threading "arrow-head" and then hold it on your cutting tool and adjust your tool post so that the back side of the arrow head is parallel to the work, and tighten it down. That puts the cutting tool as close to perfect as you can get. Run it slower and never run it out once it's in the cut. Stop the chuck and reverse the direction. (Do a dry run). Take a cut to the end of your run, and then reverse it and go back to taw and take another cut. If it takes another cut, go ahead and take the cut but NEVER disengage the threading gear (saddle drive), because you can never get it exact if you do. I don't know about doing things with the X & Y electronic help. I learned it "Old School". I was a tool & die maker in the 70's. Thanks for your video and for bringing old memories to light.
I never leave a threading tool in the thread form and reverse the machine. The backlash could instantly destroy the tool and part. Its OK to leave the halfnut engaged, but retract the tool is my standard practice.
@@joepie221 Exactly my thinking. I have heard people say they should just reverse the lead screw with the tool at depth and I have no idea why they insist on that because for the very reason you mention backlash will ruin the thread. I never knew how many misconceptions there were in some people's minds around threading on a manual lathe until I watch this video and read the comments🤣
To those wondering about the origin of the myth: Cutting using only the cross-slide instead of the compound set at 30 degrees (with a full 60 degree tip, of course) will cause the cutting action on both sides of the thread profile to make chips that collapse in towards each other on top of the tool as they are formed, which can tangle and jam and chatter. Cutting on one side of the thread OF COURSE will shear off a tiny bit off of the other side equal to the depth of cut, just like any other facing or turning does, but it lets the chips fly free and unhindered. The final light cut at full depth using the cross-slide will cut on both sides to clean up the small amount of stair-stepping you get if the compound is set 1 degree over* 30 (which was preventing you from constantly dragging the whole "unused" edge on your work while hogging the thread). *I originally said 1 degree under 30 leaves steps, which was incorrect.
Sorry I have tried to say the same thing
I hadn't seen your comment
Correct.
The way I explain it to anyone who should ask is.
The reason you set the tool at 29 degrees is to reduce the load on the left side of the tool.
The tool does in fact cut on the left side but only by that one degree to the depth you just dialed in.
You do end up with a stair step but no where near as pronounced as you think.
At compound < 30 degrees, you do NOT have ‘stair stepping’ both sides cut. The thread form tool is set perpendicular to the work piece center line after the compound is set at whatever angle < 30 degrees you like. Not sure where the confusion comes from; but if you just want to use the compound, go for it. But like the POST says, you’re gonna have chips rolling onto themselves. Also, note: not sure where you guy’s are talking about .030 or .060 cut depths and at 250+ rpm ! As professional gunsmith, I’m at 60 rpm, first pass .008” and then less and less depth of cut as it progresses. Using a 14” Monarch very heavy lathe or the Clausing medium size lathe. Also, Joe, love your left to right threading videos; but when work is between centers… you crash if you let carriage continue on while you twiddle your fingers. Hahahaaaa. Thanks Joe, on my gosh we learn SO much from you !
29 degrees, if everything is set up accurately, will NOT produce a "stair step". Anything from 0 degrees to 30 degrees will cause cutting on the right edge of the tool bit with 30 degrees being the case where tool bit and machine flexure would be causing some right hand edge cutting when mathematically (geometrically) there would theoretically be none. However, greater than 30 degrees (or any of the many set up errors people can make) will produce a stair step.
Thanks to those who pointed out my mistake. 29 takes a skim pass on the secondary face leaving a clean finish with minimal loading on that face, and 31 leaves a slight step which would need a final skim pass with a plunge on the cross slide. I've edited my original comment so as to not lead astray future readers.
Realistically the 30 degree feed trick does one thing, it reduces the minimum force required to cut a thread, for a big machine it may not matter, but for a smaller machine, or a less rigid part, it can make a difference.
Yes of course it can David you are totally correct. Those of us with small machines have found that out a long time ago lol
No it doesn't. Because of backlash the leading face of the tool always does the work. The reason oldtimers say to set your compound @29.5° is for feeding w the compound. This is an old school way of keeping track of your thread and w the wide adoption of the dro is almost never used. There is a reason for everything
@@Rough_cut613 So you think cutting a chevron shaped chip vs a normal chip is the same? some of the cutting force is shaping the chip, think about the forces needed to bend a strip of metal, vs an L shaped piece of metal. the L shaped piece requires much more force to bend.
I don't know if this is still a myth, but I was taught to step using the compound because the cutting tool is more prone to chatter if both sides of the tool are equally loaded. Cutting primarily with the leading edge puts force against the tool holder in the ordinary location and direction.
Joe, firstly let me be clear that I have great respect for your immense skill and experience and I have learned so much from your excellent videos.
So, with the greatest respect I think the issue here is that the original 'old school' teaching has been mis- interpreted and mis-quoted by generations of later day armchair experts.
The old school technique was to set the compound at 'slightly less' than the thread angle so that the tool cut 'mainly' on one side, inorder to reduce chatter on small, primitive, non rigid, hobby lathes when cutting coarse threads . There was no mention of the tool not cutting at all one side. Somewhere over the passage of time 'slightly less' became the (incorrect) 'rule' that you had to use exactly 29.5 degrees (for a 60 degree thread). From this, it was a small step, to develop the incorrect belief (myth) that the tool didn't cut at all on one side.
So, while you are totally correct to debunk the myth about only one side of the tool cutting if the compound is set at 30 degrees I don't think that undermines the value of the offset compound technique
for small hobby lathes trying to cut coarse threads, but it's important that newbie lathe operators realise that '29.5 degrees'' isn't 'gospel' , it really means a few degrees less than 30.
Regards Paul in NZ
Thank you for your comment. Feeding a threading tool with the compound set at an angle, greatly reduces the tool load and is a huge benefit for a lighter machine or small diameter part. My work and machinery allows me to just feed straight in. I thought debunking the myth may help to clear some fog.
Cutting tool loading is the same regardless of in-feed angle. It is the Depth of Cut that is the primary factor in cutting tool loading. Greater the cutting load on a specific cutting edge will wear that cutting faster.. It is all a trade off.
@@joepie221
Interesting demonstration. I never even knew threading was a complicated thing until I got on the internet.
Here, here!!
Or is it There, there? Meaning "there" will always be those who just have to make something simple and straight forward way more complicated than it really is!!
it's always funny if you do something and have great results, then some know it all comes along and just adds a few unnecessary steps ^^
Well, some threading videos are still plain bumbling made by bungler.
Lol, Machinery's Handbook (27th ed.) devotes 305 pages to the section "Threading", and that doesn't include threaded fasteners. It's a HUGE subject.
very true statement
I never heard that the back side of the tool didn't cut but just that you wanted the leading edge to be performing most of the cut and the trailing edge to be performing a minimal cut. This was to keep the leadscrew pushing the tool under a constant pressure through the work. Not sure there's much effect on good material with a constant diameter.
All that said I know good machinists who just plunge the tool straight in with acceptable results. I still use a bit less than 30 degrees and the compound since many of my tools have side rake.
Now that is a good point! 29.5 deg will keep the slack out of the gear train. Thank you Russ.
That is what I was taught in high school metal shop as well, back when such classes still existed. I guess I just assumed that when people talked about cutting on the leading edge of the tool it was understood that meant _mostly_ on the leading edge. I can't say I've ever had anyone try to tell me the trailing edge didn't cut at all. I guess I don't get out enough.
I always keep the compound parallel with the axis of rotation. No need for the compound to be at 30 degrees,
@@seantap1415 I DID NOT KNOW THIS i have all ways had set at 29 ish with a carbide tip tool would this work using your way of doing a thread or is your tool a ground type
Russ Kepler; That is exactly how I read all the instructions when I taught myself from books and videos from such as our esteemed Mr Pie. The idea, as I understand it, is to reduce chatter caused by both sides cutting equally. It certainly works for me on my 100 year old Drummond 3 1/2" centre (7" swing) lathes - as long as I engage the tumbler reverse the right way to not get left hand threads :-( You might guess that I have to set my compound at 27 1/2 degrees :-)
Is this a myth? I've never thought that anyone was literally saying they right side of the tool doesn't cut even a little tiny bit, just that *most* of the cutting happens on the left
Aye, he missed the point of the 30° methode. Confusing, assuming his knowledge he may have for his age. (Age in a good manner)
@@Voxters sorry but I have seen it written in a number of places that the RH side of the tool does not cut but Joes demonstration shows that to be false. I only hope you have half of the experience that Joe Pie has mate, if not keep the mouth closed lol
@@samrodian919 Seen it WRITTEN hm? ;)
No one said, the backside doesn´t cut. It removes exactly that much material which you move forward with your tool and smoothens the backside. Thats why Joe endet up with Staircases on his "removed backside" Tool.
Stop reading silly tweets, grab pen and paper, cut it out and try it yourself.
(Because sometimes, threads are left-handed...)
The ratio of cutting by 'front' side of tool vs. 'rear' side of tool is going to depend on feed rates and thread profile's angles.
If you could get things set up just right, you could probably get it so the 'front' side does ~99.9% of the cutting, but, you are not going to like the result: as Joe mentions, that surface of the other side of the valley is going to be really crappy & grooved: who wants that?
If you are doing some very large batchwork, (depending on materials) it *might* make some sense to do a little trig', and come up with an approximate cutting ratio, to help guide your tool changes/maintenance.
Thank you for validating what I've been thinking recently. When I think about the interface between the tool and the work, there's no difference between using the cross-slide, the compound, or increased stick-out of the tool from the holder (leaving aside the loss of stiffness from this) to achieve the next deeper cut. The geometry stays the same. The work can't see the compound whatsoever, only the tool.
Wow, Joe, great minds think alike; my machine shop instructor went through a very similar tutorial almost 50 years ago; thank you for the memories. I enjoy watching your tips, tricks, and how two’s, thanks for taking the time to share them with us.
Play safe from Elliot Lake, Ontario, Canada.
I’m happy you did this video, because I’ve never been able to convince people of this. It seems logical to believe that the tool only cuts in the direction of movement, so that’s why people believe it. But each time the tool is moved in, the rear is also moved in, so it cuts off the rear of the thread. It’s always been obvious to me, which you demonstrated extremely well. When you move the 30 degree tool in, either by using the compound, or the cross slide, you’re moving it in towards the center of the piece. With just 30 degrees, you have to leave a step on the rear of the cut, because there’s no edge to remove the step. No matter how the tool is moved inwards, it’s moved in step by step, which leaves a 90 degree back edge. It don’t understand why that’s hard to realize.
Guys, no matter where you go, whether it’s people on UA-cam doing machining videos, some of whom who should know better, or even machining articles, say that moving it in 30 degrees with the compound just cuts on the leading edge, and supposedly is lessening tool pressure in doing so. I’ve read this innumerable times over the more than 50 years since I first started doing this. It’s so ingrained that nobody has ever tried it out publicly, as far as I know, until Joe just did here.
I began my machine shop training in 71 and was taught this fact entirely in the classroom. I've tested it more than once "accidentally" by less than a perfect 60 degree cutting tool. I was taught "threading is always with a form tool", we did have "NC" back then, even as CNC was only beginning to be mainstream in general service machine shops. We were also taught to take one last pass with the cross slide of a thousandth or two to ensure the form of the thread came from the tool form.
I think that using the compound slide for the incremental infeed when threading has many advantages,
A: reduces the load on the tool. only 51ish% of the total length of the tool actually engaged with the work, both sides, is really doing the cutting, Drastically reduces chatter
B: this allows you to set the cross slide handle to a comfortable position for fast and easy retraction each pass and back to 0 every time, no number to remember
real nice for large deep threads!!
C: chip control, if all I ever did was brass not only would I be a happy camper and none of this would matter, BUT straight in feed large diameter internal threading
in 304/316 stainless makes the shittiest chips you can imagine.......
i use crossfeed only for fine threads, compound for coarse threads. At what pitch do I change techniques? It depends on the material, the machine, the insert...other factors that I can't think of right now...
GASP Joe! you threaded towards the chuck!!! Nice demonstration, Pierre taught me to thread straight in plunge cutting and it has not failed me yet.
the only time i have used the compound is to pick up an existing thread.
I have been using the cross slide for threading for over 50 yrs and never had a problem yet. Only use the fiddle slide to pick up a thread.
Great demonstration of thread cutting using a compound angle tool vs a leading angle tool cut only... I suspect the trailing angle of the cutting tool is also stabilizing the torsional vibration being generated, when using only the leading angle of a cutting tool .
"Only the left side cuts"
That is true up to a point...
On the other side of that point, the right side starts to cut. I see what ya did there.....
@@joepie221 😀
You only need as much on the second side of the tool as your depth of cut so it cleans up the step. Full profile on the second side is not needed.
he said that in the video @ 14:26. Point is you still need both sides, doesn’t matter how much on the right side is needed, it’s a fact that right side is needed.
The back edge provides a wiper action on infeed. If infeed was some small fraction of the tip radius the finish would be great, like the V groove you cut with it.
I'm not a machinist but i think I'm getting the principle. Cheers ta
Set top slide at 90 to cross slide, use cross slide as accurate depth of cut (no guessing) and on each pass move the top slide towards the left 50% of depth, (right hand thread). (can vary from 50 to 80% depending on material & tool type). As an apprentice i was taught this & have been doing this for 50 years with out a problem. This takes the excess force of the back face, It has no chatter, the finish is perfect and the depth is very easy and much quicker
Yes! The 29.5°/30° on the compound is meant to help reduce tool contact and chatter. PS Alternating flanking or ziz-zag threading on a cnc is awesomeness.
Indeed, the other side of the tool would need to be a minimum length of whatever your feed on the compound is. Love your technique of measuring thread depth btw. Been using it for a while now and it's super helpful, thanks! 😊
Thanks 👍
The idea isn't that the tool doesn't cut on the backside. It's that the bulk of the cutting is done on the leading edge and all the back of the tool does is basically spring cut what is missed. That's why I never use the compound to cut fine threads....it's just not necessary. Now start cutting 4 tpi in 4140 ht and yeag compound all day long. The tool still cuts on both sides just not nearly as much when the compound is used. I run big machines and straight in works perfectly fine for most alll threads
Yet some experts still say it doesn't cut on the right. Ridiculous.
@@joepie221 UA-cam experts haha. Glad you made this video to show them they are indeed wrong
In my experience you have to have a really beefy lathe to get good results with direct feed, otherwise I use the 29.5 deg angle. I always do a spring pass at the end too- I do this by manually pulling back on the tool post without moving the handwheel. You usually get a few tenths play away from thread contact this way, and you can reverse the cut with tool still at depth- but hold back as it passes the thread- then let go when you get back to start, and re-engage the leadscrew to cut. The effect of this will be removing an extremely fine amount of material for the spring pass, cleaning up the thread nicely. Direct in works well too I noticed if hard turning threads on hardened materials, like Bearcat 44 drill rod, or Viscount 44- using the compound on a Harrison 500, it would just spring against the cut. Sometimes a direct in cut works best, but I prefer 29.5 deg.
I have run large threads with part of the thread tool relived to help with chatter but you have to leave the nose of it in tacked. I've cut some extremely large threads (like 1/2 TPI) on some relatively small lathes with just a narrow grooving tool with only the v formed on the end. You just have to run the tool up and down both flanks of the thread, takes a while on a manual lathe but works.
Yes, I agree. I used the same technique to cut threads up to 5 mm / 5 TPI an my small Emco C 8 lathe. It takes ages but you can cut really large threads this way.
@Joe I love your clear and instructive videos - always a joy to watch.
I’m mostly a mechanic, but yesterday I needed to lengthen the threads on a bolt to make a jack screw to pull out some flanged bushings. Anyway, I set the compound to 29.5°, or 59.5° on this lathe, like I was taught in school. Then I needed to square the tool, but I couldn’t do it against the face of the chuck because the tool had a weird offset, so I asked one of the machinists if he had a fishtail gauge. He didn’t know what I was talking about… but he just lined up the tool in the existing threads. I felt dumb.
But he also asked me why I had moved the compound. He said he always cut threads by feeding directly with the cross slide.
He said it’s a carbide insert and the lathe is strong, just go for it.
And indeed I cut the best looking threads I think I ever made. The irony is that I learn to cut threads in school using the same exact carbide inserts, but I guess the teacher wanted us to learn the hard way… Or maybe he didn’t even think about it. The HSS tools were just cut from the program 3 months before I started.
Still, the machinist was surprised that I knew how to cut threads, especially metric threads, and that I knew my way around a lathe. I pointed out that I know every machine in the shop literally inside and out because he breaks them and I repair them… haha.
That's neat that you have all this and the thought put into it, the time spent, and learned more by doing.
I change bushings like you describe with a c-frame and forcing screw. The ends are selective for different size bushings.
The biggest lesson when being paid only book time labor for a technician, other than a trick that's super fast, is using the right tools to begin the job and be done with it on time.
At your leisure, on your own car, you can reinvent the wheel while you're at it.
Nowadays you can use a tool and return it quite often at the parts store or get it cheap at Hebrew freight.
@@dannylinc6247 In this case the bushings were already tapped for the use of jack screws, but we didn't have M16 allthread on hand.
I say mechanic but I'm a millwright in a fab shop. My team does all the shop maintenance, in addition to repairs and modification on all kind of customers equipment of all sizes.
My speciality is mostly electric controls and hydraulics, but I'm an OK welder and machinist. 90% of the time when we need a tool, we make it in the shop.
Also we're in a pretty small town, way north of all the big cities. If we need something it's not next day shipping but next week shipping. And with Covid it's next month shipping now.
@@felixar90 thanks for the clarification
Glad you found your calling.
@@dannylinc6247 Yes I did find my calling. I used to work in IT, but I got sick of it. Went back to trade school.
Agree completely, I was taught the 29.5 deg method long ago, but I plunge everything nowadays. For me results are the same or better in difficult materials as well. Perhaps it has to do with modern carbide tooling. Carbide does not like rubbing, in my mind a properly rounded 60 degree tool should actually perform better plunging since depth of cut will be more consistent around the tool. I can speculate that perhaps sharp HSS tooling and less rigid lathes may perform better the old way.
Is that one half of a threading tool what you would use to cut a buttress thread?
Great idea there. I guess you would feed in with the cross slide instead of the compound.
Joe, again great content! I sure wish my dad was still with us, he was a humble self taught machinist and like you was a genious. I used to send him ytube vids on discs and would have sent him yours as well. Many things I'm certain he would have said "Ya, ya, that's how you do it" yet on other things he'd say "Oh, that's a good way to do it!" I've learned much from him and learn much from you. Thank you for your knowledge, experience and humble way of teaching, that is what keeps many of us coming back for more. God bless.
Thank you for the comment.
I've never heard that said. The reason for setting up at an angle is to reduce the load on the tool and work. It does cut a little on the back, but nowhere near as much as if you plunge straight in. When you're cutting a long coarse thread on a difficult material, you don't want the job climbing up over the tool. It also makes it more convenient on manual machines, using the cross slide to come back to zero.
See how inconvenient it is, plunging straight into the work, having to keep track of the depth of cut each time.
Ignore the depth of cut. The PD and tip flat dictate a good thread.
@ Roger Froud- your explanation is exactly what I was taught by the old machinist teacher that taught me over a decade ago. I was never told by him that the rear of the tool didn't cut- he had me set compound at 29.5- it didn't rub as much, just as you said. You absolutely do need the rear of the tool angle- Joe's totally right on that- I have no idea who the hell came up with this idea that the rear of the tool doesnt cut. Of course it does! Joe's right about not worrying about your depth of cut- I couldn't care less about that- you just cut the major OD for external threads, or minor for ID ones, and cut until the thread fully forms to it- the last little bit is usually hand fit or thread wires or thread mic anyway
I heard of that but chalked it up to the left side taking the brunt of the forces allowing the right side to maintain at least some contact with the work.
True
The question is really one of tool pressure and direction. During normal left to right turning the lead screw is driving the carriage towards the chuck. Cutting forces are maintaining constant pressure forcing the carriage against the lead screw (to the right) and the spindle against the tapered bearing or a thrust bearing if plain spindle bearings (force to left). Atlas lathes like the one I have are designed around these forces. The lead screw will be forced to the right as the carriage is forced left and so Atlas made the pillow block support on the right end of the shaft deliberately weaker so it will protect the lathe. The right side of the tool will cut during threading but I like to keep it to a minimum. If the tool pressures on the right and left cancel each other the carriage COULD drift. If the tool pressure on the right side somehow exceeds the left pressure then the carriage may jump as the slack comes out. Bottom line if you have a nice tight machine plunge in at 90 degrees, if you have a lot of play like my old machine you got to deal with it.
Keep some drag on the top of the handwheel during threading and take control of that slack.
I've always used a 60 degree tool sharpened at about 50 degrees, with a full radius on the point. Because of the radius, which cuts on the back side, I have never detected any stepping at all. Every thread that I've ever seen has a radius at the bottom--a Sharp corner creates a stress concentration which encourages breakage.
I believe they are 'J' threads. Not all threads can have a root radius and still work.
With the speed you are running and pulling out of the groove and moving back to the beginning of the cut with the lathe still running, how do you get the cut indexed in the correct position? Decades ago, and older machinist showed me a threading procedure as thus: He ran the lathe very slow, made a forward cutting pass, and stopped the lathe. Then without disengaging the carriage backed the cutting tool out a few thousands and reversed the lathe to get back to the beginning of the cut. Stop the lathe, still without disengaging the carriage. Then set the tool for the next cutting pass and go forward. Note that the carriage is never disengaged so that the tool is always indexed to the groove being cut.
Many lathes have a small numbered wheel that allows you to disengage the half nut and reengage at exactly the same starting point.
@@EpicZombiez2314 I learned to thread using the dial, slowed me down a bit when I moved to a different shop where none of the machines had a functioning or present dial. At least now I can do it both ways.
@@EpicZombiez2314 Thanks for the explanation. I guess the lathe I was shown that procedure didn't have that feature.
I've just sketched out the path the single point takes with the compound slide set at 30 degrees and it shows a small triangular section that is cleaned up at each new pass of the cutting tool. This clearly shows that a full 60 degree tool is needed to form the thread but only a small section of the back edge of the thread equivalent to the depth of cut is removed from the back edge at each pass. The sketch also clearly demonstrates the ragged side of the cut as demonstrated in the video if only half a tool is used.
You’ve done a perfect job of explaining why cutting a staircase thread with a weakened tool would be stupid.
In theory the only part of the right side you need is equal to the amount of infeed, the size of one of those steps. The entire rest of the right hand edge is superfluous.
On a side note in cnc canned cycles for threading in several of the cases i have come across the tool path as far as the feed is concerned can be controlled as a right, left, or both sides with each pass. Left the right then left and right descending offset as to put a larger or smaller per chip load on the sides of the tool. Including a straight down feed as well perpendicular fo travel. In all things manual this is a user subjective approach and confidence. Final pass should always be both sides more or less and always with a full form tool. Joe you nailed it on this video. The fancy stuff is simply for tool life management and chatter control. I think Kimber commented his lack of a compound,. He may have less chatter than a 29deg angle with a compound in overall ridigity. The comment about chatter in plastics is all reduced to tool material and rpm. Super honed tooling is best for plastics with high positive geometry and a chip pocket, imagine a knife blade reaching up into the part.
I hate carbide on plastic. HSS is a step towards success.
My first attempt at cutting a thread produced the ugliest screw you can imagine but the nut didn't seem to mind so I used it anyway rather than spending another 5 hours trying again. Changing the gears on a mini lathe is a job in itself.
There is a very important distinction to be made here: the 30* compound setting is relative to the cross slide axis. I.e., it is the angle off of perpendicular to the spindle axis. If you're thinking "Duh, what else could it be?", on some lathes the compound angle is relative to the spindle axis. I.e., 0* is parallel to the spindle axis, not the cross slide axis. On these lathes the compound is to set to 60* for threading!! It's the same position in both cases, it's just the reading on the scale that's different.
I see the 60 degree thread profile as a flashlight beam in a dark room. You set your compound within the light and off ya go. Whether the index mark says 30 or 60, you have to be in that beam.
I have never used the compound slide offset from zero when cutting threads, so I've never even considered it possible to form anything that would resemble a 55 or 60° thread with a half form tool? I've only ever used the cross slide for depth increments, a full form thread cutting tool, and the chasing dial to synchronize. Then I test fit the mating part wherever possible before removing the finished part from the chuck. The form and fits come out perfect every time👍🇦🇺
Same here with with 55 years machining experience apprenticed in a shipyard, never turned the compound slide for screw cutting and always worked fine:-))
@@johnhili8664 Yeh, and by using the compound slide set on an angle to make depth adjustments, wouldn't that screw with correct thread engagement when using the chasing dial?
@@simonilett998 That's another thing I never use chasing dial as even those can make mistakes especially on fine threads!! I always reverse the lathe, for my hobby stationary engine collecting I have a Myford Super 7 and a Colchester Mastiff!!
@@johnhili8664 Yes, I think the chasing dial is only good for coarse imperial threads from memory, and you don't want to move the carriage when using it or it could throw off the position. I was taught the same, pretty sure from memory I leave the lead screw lever engaged, drop the feed into neutral and back out the cutter after each pass, then switch the feed to reverse to keep everything tracking the same, and it takes any backlash etc into account too.
@@simonilett998 I think it does not affect the timing but still I cannot tell as I have never used it in my 55 years experience:-)) Here have a look at some of my steam engines ua-cam.com/video/iyvqs5Fb4Oo/v-deo.html
Joe anybody who doesn't understand this concept should not be anywhere near a lathe. Great video! 🤗
Yet they make tutorial videos and people continue to blow smoke up their skirts. Baffles the mind.
In Australia we don’t set the compound to half the thread angle but advance the compound slide a small amount to reduce the cutting on the left hand side of the tool. This reduces tearing and improves the finish. I used a ratio of 1:5 which worked for me.
This is what is needed with hand ground high speed steel tooling with no side or back rake. With introduction of carbide insert tooling with magical tip geometry I think the need for advancing the tool is not needed anymore.
My Sherline actually does threading fine using only the cross slide. Of course, it doesn't come with a compound. I've never done coarser than 1/4-20 though.
I also have a Sherline, (and love it) but I have done threading on larger machines and as good as a Sherline is it, it can not make nearly as deep of passes in threads. That is the difference.
Joe, you failed to mention the reason why using the compound for thread cutting is the industry standard: it's all about reducing tool pressure. Your demonstration on an extremely soft material like brass is kind of ridiculous. Using a harder material, like 4140PH or 304, and doing a direct comparison using the same form tool, with identical rpm's and feed rates, would have demonstrated that the compound method produces smother threads. That's why it is the industry standard method.
Which one is the industry standard...??? Compound slide for reduced tool pressure or cross slide for smoother finish?
@@pinkpandavideos Thank you for apprising me of my mistake. I corrected it :-)
It's more like UA-cam standard. You cut them the fastest way in the real world. Adjusting compounds in every turn isn't fast.
@E Designs thanks 👍
@@MF175mp Using the compound for threading was the standard LONG before the internet or computers even existed. Real world machinist typically keep the compound set at 29½° and it doesn't take us any longer to cut threads doing it correctly. Using just the cross-slide for feeding is a lazy method, not a good method, and Joe is doing a disservice to his audience by promoting a bad technique.
so as a guy that runs a cnc on the daily. I can tell you this will work perfectly and has the advantage of reducing chatter if you clearance one side of the tool. (staggered cut can be even better)
if your tool has a 0.004" radius at the tip, you want your compound in feed to be about 0.001" per side for a decent finish. definitely not a fast way of doing it, but it will save your but sometimes.
Excellent clear demonstration of what is actually occurring during a single point threading operation.
It is my understanding that the oblique approach was to reduce chatter by using the leading edge to remove more that the trailing edge.
Thanks for sharing, best regards from the UK.
Being something of a single point thread cutting fan i have heard the hard of thinking say how you have to set the top slide at half the angle. Well never taking advice without confirmation i experimented cutting some stainless with a full form insert both angled and straight in and looked at the results under a microscope and you couldn't tell the difference. What is the problem if the tool does cut on both sides? Is your lathe made of cast iron or licorice. The top slide is more useful left at the correct angle, in line with the lathe axis and marked zero on the degree mark.
Joe, could you do a video on the idea of tilting a threading tool to the thread helix angle, and explain how that does or doesnt work? I always thought if you did that one side being lower than centerline would smash, and the other being higher it would rub and not cut, but supposedly it's an advanced technique some would use, and I've always been curious how that actually worked or didn't work at the cutting surface. In fact it's one of the few things about cutting geometry that still confuse me when I can understand some otherwise very complex tooling. Can you cover that sometime?
This practice of cutting threads via feeding the compound set at 29.5/30 degrees appears to be a very American tradition that was practiced nee 100 years ago when lathes and thread cutting tools were very different than they are today. Back then majority of cutting tools were high speed steel and often cutting edges were ground by hand. Due to the tolerances/precision/accuracy required for proper threaded parts to function, it might be possible to compensate for cutting tool dimension issues. SO much has changed with threading tools since then, Same applies to engine lathes made today. Yet, these century old American machinist traditions persist in the very different machine tool world of today. Looking at how single point lathe threading is done in Japan, EU and other parts of the world, thread feed is done direct in using the cross slide.. this feeding via the compound set to 29.5/30 is virtually unknown.
Personally, learned how to thread about four decades ago from a master machinist in a tech company model shop on a Hardinge HLV-H, no feed via the 29.5/30 degree compound, thread cutting feed was direct on with the cross slide using a carbide insert threading tool. Start threads with modest cuts, maybe 0.01" with progressive smaller cuts as the thread depth increase to about 0.002" per cut or less to achieve the required thread dimensions. To this day, cutting threads are direct in feed using the cross slide.. Regardless of thread pitch or thread form.. Proper Selection of threading insert, feeds, spindle speeds and all for the material being worked on can and does make all the difference in finish and results.
Fact is, threading is a form tool operation no different than cutting a groove, part off or similar. As for chip formation and clearance it has much to do with cutting tool geometry. Today, carbide threading inserts can easily achieve levels o accuracy/precision/tolerances and cutting geometry not possible in decades past. Add to this carbide and coatings used on high quality modern threading insert completely alters how thread cutting tools function in every way imaginable. Consider how ACME, Buttress and many other non-triangle thread forms are made.. With the majority of these non-triangular thread forms, this "business" of feeding with the compound at some is absolutely not done. As for chatter and poor thread cutting results, that is more to do with cutting tool and set up rigidity, stability, feeds and cutting surface speeds related to what the material being worked on requires.
As for threading away from the chuck, there is about zero reasons to NOT thread this way.. Unless the lathe has a right hand threaded on chuck. For lathes with RH threaded on chucks, any operation with the spindle running CCW greatly risk unscrewing the chuck.. resulting in a near instant disaster.
There might be a little baloney in that long winded explanation...single point threading has barely changed in the last century. Feeding at 29.5 allows the leading edge to bear the main cutting force, so chatter and vibration are absolutely reduced. It's only for roughing, as you want both edges engaged for the finish cut. If it's not needed or used in most of the world, why does my Japanese CNC lathe infeed at 29.5 degrees??? Maybe because it works!
@@peoplepower1272
Fact is the edge moving in the direction of cut does the cutting, once the DOC has been set regardless of how it was set (angle indeed-via compound or etc) or radial infeed via compound or etc.. This act of metal removal is not static, it is dynamic and due to the fact the metal bits involved (cutting tool and work being threaded) are moving changes the perception vastly.
This angle compound infeed belief/idea comes from the reality threading tools were hand ground nee 100 years ago. Since then modern threading tools have vastly changed far beyond hand ground high speed steel cutting tools and carbide insert geometry. Ponder how many production cnc machines today use hand ground high speed threading tools...?
Here is a chart from Mitsubishi, carbide threading insert manufacture.. Direct radial infeed is recommended with their threading inserts. Not just radial infeed, the depth of cut per pass is also recommended. Why is this, modern carbide threading inserts have chip formation geometry moulded/ground into the insert that negates any need for this angle infeed for threading. Bottom line, believe threading cutting beliefs/ideas from nearly 100 years ago that was based on cutting tools and machines that are of that same age or accept the fact science and technology has moved far on from those ideas/beliefs..
www.mitsubishicarbide.net/contents/mhg/de/html/product/product_guide/information/turning/threding_ex_03wit55.html
BTW, there are full form threading inserts that cannot be used with angled infeed...
As for cnc lathes, virtually any type of cutter infeed can be programmed as needed and this does not apply to any specific Nationality of cnc machine.
This is the way I learned to thread but I don't remember anyone claiming that only one side of the tool was cutting.
Joe, You are absolutely right Again !!! Thanks a bunch ! Joe , you are always there to help those of us who need to learn at home and on the job. Paul Kerst Glen Rock PA.
Thanks Paul.
I was taught to single point by several old timers and this is the first time I've heard this nonsense. We keep our compounds set at 30 all the time, when I asked why, they said it was so you could "pick up" an existing thread and fix it. I've been cutting single point threads for over 20 years in a production shop, both with and without a compound. If you have ever actually WATCHED the tool cut, you can easily see it's cutting on both sides.
I'd bet it's an idea spread by folks that have only been trained on regular lathe work, and never used their brain enough to ask if it makes sense for threading. If you let them do something they're not actually trained on, they'll probably break tools.
@@taxicamel 25 years in a PRODUCTION shop and you come along and claim I don't know where I work, that's hilarious. "You DO NOT "pick up" any threads in a "production" shop situation." You ever heard of REWORK or CUSTOMER REPAIRS? You don't send PRODUCTION parts to MAINTENANCE to have them reworked. Have you EVER working in a machine shop or did you just read the WIKI article on single point threading? The ORIGINAL argument the video was covering what the idea that a single point threading tool ONLY cuts in the leading edge. This isn't true, and even YOU said it isn't true, but you're like 'well, yes it does cut on both side, BUT it cuts MORE on the leading edge' SO? it is STILL cutting on both sides, just like I OBSERVED. ALSO, I have single point threads on THOUSANDS of parts on machines WITHOUT a compound, and in those cases the threading tool DEFINETLY cuts on both sides. As for if I would listen to someone, sure I'm always willing to learn, but that someone would need to know what they are talking about, which leaves YOU out.
I don’t understand something here with the 29 degree thing. Is the tool set with the center line at 90 degrees to the work with the compound at 29 degrees? Or is it set at 90 degrees to the work with the compound at 30 degrees then the compound is moved to 29? If the tool is 90 degrees to the work then you will get the profile of the tool as you are threading regardless of the compound. If the compound is moved after squaring the tool then you are not cutting a 60 degree thread. It seems like the 29 degree thing is meant to compensate for deflection while moving sideways while cutting resulting in an accurate profile. With a rigid setup it doesn’t seem to be necessary.
You're not going to like the answer but.....it depends. American (and I believe UK) lathes reference 0° from perpendicular to the work and import (Chinese specifically) reference 0° from parallel to the work. Essentially the idea though is to advance the tool with the compound (aka top slide) at 30°, the same angle as the flank of the thread so you're only cutting with one side of the tool and hence not pushing it as hard as when you just plunge straight in. Joe's clearly debunked this simplification of the process but on smaller lathes, the idea is to reduce the tool pressure to something it can handle. Why 29.5°? It doesn't matter if you're at less than 30° (I'm assuming a 60° threadform here but otherwise half of it), the right side of the tool would just cut more ... but you cannot be over 30° so 29 or 29.5° just err on the side of caution.... because if you're on an import lathe like mine, when it says 30° (or rather 60° on an import!>, that could be 29, 30 or 31....on a good day! Incidentally, Joe's got good videos of how to set your compound accurately for when it does matter.
Tool perpendicular (90°) to the work
Compound at 30°
Can't believe I missed this when it came out. Well demonstrated and explained, and it makes total sense.
I’m lazy - I just plunge in on the cross slide - can’t be bothered moving the compound .
I also find that not having to trig out the feed for the compound easier . With the compound set to half the thread angle it still cuts on the trailing side but the bulk of the cut is on the leading side which can help to stop chatter or a dig in on light machines , you also have to be careful threading up to a shoulder or in a blind hole as having the compound set to half the thread angle not only feeds the tool in towards the centre axis but longitudinally so the little bit of clearance you had at the start can disappear and you end up driving the tool into the shoulder or bottom of the hole . Threading away from the chuck fixes that problem !
Thanks for the fantastic video Joe , I know this has been picked up on one of the model engineering forums and I look forward to the ensuing squabble it will cause 🤣
The biggest advantage of the compound slide set over at the angle is when you are threading the end that needs tailstock support. Then the angled compound gives more room with some machines. On other large machines it won't make any difference which way the thread is cut. A lot of cnc machines will use a zig zag approach, where the left hand side of the tool is used first, and the 2nd pass it will use the rh side of the tool second, etc and finally uses a plunge cut to clean up both sides at the last cut.
Enjoyed the video and reading most of the comments/replies….I book learned compound, never attempted a change as it works even though years ago I understood that plunge cuts also produces the same thread….time for me to modify my methods….tks
Hi Chuck. Thanks for stopping by.
Hi Joe, as a retired toolmaker I find your videos of a high caliber and informative for many wannabe engineers . As far as threading is concerned I thought all my Christmases came together when I got hold of full profile carbide inserts ( many moons ago ) from a reputable brand . I soon found out how accurate these inserts were by comparing the effective size with the OD and found that working to a tolerance you didn’t need to measure with those horrible screw thread micrometers and could solely rely measuring the diameter ( crests ) with a standard micrometer and as a bonus no burrs . I am sure you would be aware of this . Happy screw cutting !
Most of the time I ignore the compound for threading, simply because it's rarely on the machine anyway. Heck, I just cut a M42x2 thread in cast iron at 650 rpm, 'cuz that's as slow as my beast goes, with minimal issues, except the terror of a possible crash.
Your right it dose cut the right side as well how ever by doing this that cutting length is minimal being only the length of your tool move. The means your only cutting load is still only 55% percent verses a full cut all across both sides of the cutter meaning 100% cutting load.
CNC lathes (Siemens 840d control, ShopTurn) offer an alternating left/right cutting cycle for threading for better wear and finer threads.
Could you do a follow-up on cutting the thread only on the cross slide, vs with the compound at 29.5, 30 and 30.5 degrees to see if there is a difference in chatter marks and on which face(s) they occur? Maybe it has to be in a harder material?
I'm pretty sure in his other videos he's stated that he never uses the compound to cut threads, always feeds straight in with the cross slide. So pretty much any of his videos where he threads will be with the straight in method.
29.5° will shave a slight amount off the right side with each pass, 30° will shave none off the right side with each pass except for the DOC at the tip of the tool and 30.5° will blow the thread profile! :-)
I have no idea why anyone would imagine that the 'back' of the tool is just there for decoration ;-)
Even a simple electronics guy can see that threading is a 'form tool' operation ...ah, well, myths have to come from somewhere, always fine to see another video from you, sir, even a 'myth buster' ?
I was thinking the same thing. I`m no machinist, I`m just a guy who bought a chinese 500mm lathe ... and I figured that out !
If the leading edge is the only thing cutting. Why, when you buy one of the tungsten insert threading tools, do they come with both sides of the profile formed? I never understood where this, one side doing all the cutting, came from. Leave it to "Joe Pi" to throw another misconception in the wood chipper.
So the right side is cutting the depth of each plunge? So if you made a took that had 20 to 30 thou on the right side you'd get a good cut?
On a manual lathe , the leadscrew always has slack in it. The only time I use the compound is to cut a multi-lead thread. My passes are .010 deep to the last .005, then .002. All straight in from the cross slide. I let most of my passes float with the leadscrew, Then let my palm rest on the apron handle to pull backlash out of the leadscrew. This switches the tool pressure from the left side of the thread profile to the right side. The last couple of thousands has a lot less tool pressure equally distributed around the entire profile. My success rate is 99.9%. If there's chatter, it usually comes from other issues with the machine or the setup.
I apply hand pressure drag to the top of my handwheel while threading 100% of the time. A very worn half nut or leadscrew can ruin a thread if you let it float. I believe the condition is called 'Drunk" and a single light pass is not guaranteed to clean it up.
@@joepie221 I couldn't agree with you more. I believe the idea of setting the compound at 60 was in the days of HSS. Each machine has its own character as you know, but I still enjoy the manuals over a CNC. Maybe its just a control thing. LOL
@@davidvollmer959 : May be a feedback thing too. Lots of info can be conveyed by a change in feel when you change your actions...
I always thread with the compound at zero: first day of apprenticeship I was told to do this. CNC lathes don’t have compounds and they make fantastic threads. I was lucky to run a Hardinge clone during my apprenticeship, I miss her dearly.
Excellent demo to prove a point....Thanks for Sharing....!
I paused the video at the beginning to make a statement of fact. The compound is set @ 29.5 degrees so that the tool is whiping clean the back side of the tread, so when you advance the compound it keeps the following side of the tool in contact the following side of a 60° thread that is.
I was taught that the leading edge cuts, the trailing edge guides and cleans the cut.
It's a self-piloting mechanism, sort of like a 'gun-drill'.
The lead-screw is drawing the carriage ever closer to the chuck, at the same time, the trailing edge of the tool is being guided forward by the screw-threads that have just been cut!
The grind of the tool is critical: the leading edge has a slightly steeper angle of attack than the trailing edge.
Slightly hollow-grind the top face of the tool, center the 'dip' near the trailing edge.
This puts the leading lip slightly higher and steeper than the trailing.
Yeah, both side of the tool are needed, but they are doing different jobs!
The tool is advancing into the material. It is impossible for the tool not to cut on its entire DOC profile. The bias of that cut will be determined by the angle of approach. BOTH sides cut.
Think about it, when you screw cut the correct way, it's the cross slide you dial in for each new depth of cut. With the cutting tool set up correctly at 90 degrees from the work piece going through the centre of the angled tip for a standard tooth profile, both cutting edges dial in the exact same amount, and therefore both cutting edges remove the same amount of material.
This whole idea of using only one tool cutting edge to cut a thread is counter productive.
Me, I started my engineering apprenticeship in September 1976 for Philips Industries in their Research and Development department as an instrument/tool maker.
When the compound is set at 29.5, the main chip flow is facilitated since coming off only one side of the cut while the tool is well supported by the 0.5 on the other side preventing chatter. The 29.5 setup also keeps pressure against the lead screw backlash as does conventional milling versus climb milling.
If all clearances on the hss tool are correct for brass, front + pitch angle + profile and rake(perpendicular to axis), the finnished profile on work will be same as tool. Slower speed with cutting oil helps as tooling point small. I was taught set compound slide half of thread angle and also cut first leading edge then adjust slide to cut trailing edge. The 45° for buttress threads. Cheers
Yeah even if you push the tool into the work at 30 degrees, when you start the movement to make a thread it doesn’t do that. So it should need both sides
Whenever anybody says that the 29 degree setting produces a "stair step", the real reason is that that the compound is not accurately set to 29 degrees AND/OR the tool bit is not ground to 60 degrees accurately AND/OR the tool bit is not mounted straight. With everything correct, the right edge of the tool must cut a little. Assuming you could have everything perfect and chose a 30 degree compound angle, I would still expect a little cutting on the right edge just because the tool will be flexed slightly to the right due to the pressure on its left edge even in a very rigid lathe set up.
The reason for the 29 degree (or 29.5 degree by some) is to control chip production. If you cut straight in, a chip curls up and to the right from the tool bit's left cutting edge - and - a chip curls up and to the left from the tool bit's right cutting edge.. These two chips are trying to go into the same air space above the tool tip. Since that is impossible, they collide and cause stress, possible tearing of the metal, and more force on the tool tip. With free machining metals like brass, this might be less of an issue. With harder materials, it can be a huge issue. In any case, you can end up with tearing of the metal at the tool bit tip. Being a little under 30 degrees insures that at least a small amount of cutting deliberately occurs on the tool bit's right cutting edge for not only a good finish but for good contact for heat transfer.
Hobbyists may not notice some of these problems as much as they often are making smaller parts with a low horsepower machine and often very light cuts. But in a production environment it can be very important.
Dead nuts, Chuck.
That's a good demo Joe! I was taught to use the compound to rough out the thread and leave a thou or 2 for a cross-slide pass to "back-face" the thread and remove the steps. I almost always run a spring-pass as the last cleanup pass.
Having cut threads for the last 50 years, I quit feeding in with the compound more than 20 years ago. I still set the compound on 29.5 or 30 degrees for clearance and to pick up threads.
Pick up threads?
@@janeblogs324 When there are existing threads being repaired or extended.
In the 1980s, I had an order for stock sling swivels and I had to make them with wood screw threads. Wood screw threads are tapered near the insertion end of the thread. I made these by two methods; form tool and form ground grinding wheels. I must say that I have never heard of this myth of half of a threading tool. It did as I expected; created steps on the trailing edge of the thread form. In finishing, my wood thread could not have been accomplished with half of the form and since I had to cut the threads on a taper half a thread form would have looked really bad. This was a very nice demonstration of a weird myth that has come into the machining business. Keep up the "Myth Busting" and I will await your next demonstration.
Thanks for disabusing me of yet another falicy. And thanks for your usual thorough, clear explanation aided by lots of examples. For what it's worth, I'm pretty sure I picked up this one in a night class I took while I was in high school about 50 years ago. While there are those who might say that understanding this process doesn't have any real affect on the final outcome, my experience has taught me that acquiring a deeper understanding of any process generally pays off somewhere down the road.
Awesome content and demonstration...many thanks
From a practicality standpoint, it would be good to explain how to go about re engaging a new tool after a disaster of breaking the tip off
the first tool. I have a way I use, but it would be good to show how you would approach it. Thanks!
I have a sneaking suspicion you'll find that video on my channel.
I am just surprised to see Joe Pi. cutting threads toward the chuck. :)
I thought so too but,this was a demonstration.😁
I actually feel awkward doing it this way, but its easier to video.
I have been looking at miniature lay down inserts (Dorian for example) and they make UN 60 deg full profile inserts but they always specify them as single TPI. It seems like I should be able to use that cutter for any thread pitch that is higher than the one specified. What am I missing? Are they not dead sharp?
great channel, it's nice how many other good channels refer to your work.
greg
The term full profile is the key. When the root and PD fall into place, the crest of the thread also forms. You can use the insert for different threads, but it probably won't top the thread profile. You can use the 16 TPI insert for a bunch of different Od threads of the same pitch.
So then how do you cut a buttress thread? Similar grind but only plunge with the cross slide?
Yep... 😎👍
You can do it that way, or if you are a compound guy, set the compound to stroke within the angle of the smaller side angle.
If you’re set up for high-speed photography, you could probably show directly that the right edge of the tool is cutting.
I'd like to see this too - where are the Slo Mo Guys or Lauri Vuohensilta (Beyond The Press) when you need them?!
Joe, Thanks for all of the vids you have made!
Did you have to go to confession after threading toward the chuck? ;)
Damn, stole my jab at Joe!
Yep. I had to run 5 - 16 pitch, 3 - 10 pitch and 1 double lead as penance.
I love this video ! I was taught to set the compound at 30 degrees, I never really thought about it. Early in my career I learned to cut double lead acme threads with no relief cut allowed. You had to time backing the tool out while cutting threads at slow rpm. I don't think i could do that these days.
Joe, great explanation and demonstration. I always wondered about how much the back side of the tool played a part in the thread formation in a single point operation. Seeing the result makes it as you demonstrated, makes it perfectly clear. Based on this demonstration, you don’t even have to set the compound on 29.5 degrees, because it only lightens the load slightly on the backside. It does not completely eliminate it, so it may improve the finish quality but does little to nothing in forming the thread. Thank you
How does the lathe start the cut at the exact same spot each pass?
There is a numbered thread gauge dial that runs on the feed rod that tells you when to engauge the feed.
I’ve used one since 1974, still a rookie, that’s why I watch Joe he’s the expert and I learn from every video.
@@jamesschrum8924 we just got a lathe and an end mill at the plant where I have been an industrial mechanic for 35 years and I want to learn how to use them.
You're on the right channel. feel free to ask questions. As for your specific question....assuming the machine is set and geared correctly...a solid rule of thumb is to leave the halfnut engaged at all times for a metric thread and control the carriage movement with the spindle direction, for an even thread you can use any line on the dial, and for an odd thread, use only the numbered lines. When in doubt on an imperial thread, always use the same line, numbered or not.
The only people that think the right side of the tool is not cutting have never ran a lathe.
or screw machine ..die heads.
You can set it greater than 30° or less than 30° depending on which way you want the chips to curl - in the feed direction or away from it. Useful if theading ALL the way to a shoulder to keep from trapping chips between the tool and shoulder.
Joe, I am a 70 YO who has minimal experience with lathes/mills (my career has been radar, computers, high tech electronics in general) but even without lots of hands on experience I can see that statement is foolishness. It's about the same as saying you can cut off the bottom half of the 60 cycle AC and still have your negative voltage.
Its not the same thing at all John... you kinda have to see it in "the flesh" to get yer head around it...
@@peterfitzpatrick7032 : It really is analagous, even to the extent of there being odd quirks that might still generate just enough negative that someone claims they were right after all (a negative voltage can be generated because one of the junctions of a transistor acting as an LED, causing the other junction to act as a solar cell- lousy amperage, but just enough to lead the unaware on wild goose chases...).
I was always trained to use a compound. We set it at 29 1/2 °, never understood why on a 60° tool? Great video as always.
dam fine demo there if you were watching it you can see the tool cutting on both sides doing it the proper way with the half ground tool you could see clearly it not cutting on the back side just a question i use a carbide threading tool insert can you cut a thread with out setting at 29* i don't use the lathe much for threading
Short, sweet and to the point with graphical proof. How simplier can it get. GREAT job Joe, you did it again !!!!!
Can you show a simple way of doing a higbee on a manual lathe?
I may actually show that. I do it manually. With a file that is.
General Discussion: Of course there are several ways to cut a thread on a lathe. Many machinists will do the whole process without using the compound slide at all. (The Index wheel is there for a reason.)
With this method (someone else) saying you don't need "the whole" half of the tool - is a little strange, you may not need the WHOLE of the right hand flank for thread cutting - not plunging, but you will definitely need that portion of the "right hand flank" which is making the depth of cut. (make a drawing and see that parts of the tip are "working" - you need those)
A tip ground like that demonstrated also has no support - yes it is very bad....
Another way for fun - would be to blue the tool and make a threading pass to show how much of the right flank cuts in normal thread cutting (using the compound slide).
When a machining channel host presents the statement" Only the left side of the tool does the cutting" it very clearly states the right side of the tool isn't doing anything, and therefore not needed. The half tool used in this demonstration is being used just to prove the right side is absolutely needed. Its the WHOLE point of this video. I personally never use a compound and most of my subscribers know that.
@@joepie221 : Of course when claiming "a thing" in video format it would also be great to demonstrate "said feature" - which you have in this fine demonstration, thank you so much.
When I got my lathe, I did the traditional 29+- compound method. After I saw Joe's video on inside-out/upside-down, I experimented in different metals, DOCs, feeds etc. Conclusion, Joe's method is faster, easier, and gives excellent results.
No myths busted here.
The reason behind setting the compound that way is to minimize the cutting load, so most of the load goes on the leading edge which will reduce chatter. That's also why you don't set the compound to 30 degrees, you want it slightly less so it does take a very small cut on the back edge.
Yea i thought 59° was the std so 29.5° would be ideal.. but unless your wanting to cut threads on a fastener thats going to be torqued to yield or if its for a worm gear or something critical of its cut than if she threads than the nut will finish the cutting.. lol..
Regardless of the compound setting, the tool always cuts on the back edge. Maybe not as much as the leading edge, but it does. So for anyone that thinks it doesn't, that myth was perfectly busted.
@@joepie221 Anyone who thinks the back edge doesn't need to be there has no place being anywhere near a lathe.
@@Z-Ack standard metric is always 60 degrees. The point of a thread is that both the screw/bolt/whatever has exactly the same tooth angle as the thread in the nut/housing/whatever. Threads work by locking together from maximum tooth to tooth contact. Just like how a morse taper works.
As for chatter, you either have the incorrect cutting edge angle for the material, or you're not centred correctly.
Or, on the other hand, you have bearings that need changing in your headstock, or too much slop between a carriage and it's slides.
Straight in is the British way of cutting threads. I was trained to cut threads at the 29 degree compound slope, and I found it tends to give more angle on one side than the other.. I use a mix of compound and crossfeed. Last two cuts straight in. I suspect that the spiral/helix and tool bit geometry actually suck the tool ahead causing a flatter slope on the trailing edge.
The trailing edge of the tool bit may not cut per se but it does scrape and clean up the thread.
An interesting experiment would be feed the compound it at say 1 degree to the right opposite of what we normally do and see what happens.
I must be british. I plunge all my threads.
I've never bothered with the angled compound, did tests years ago and found little to no difference in the final thread so I've not bothered since.
Me either. I plunge every thing.
And me toolmaker 50 yrs always plunge cut ,never found any benefit to set compound slide at an angle.
@@johns5447 And I have done the 28-1/2 because tghat is the way I was taught. ,,,,can some body get a sleever or big spud wrnch and help me get my foot out of my mouth. - Iv'e always extracted my foot that way. too so it must be the right way. ;).
But an interesting idea-- use your setup for this demonstration to thread both bolts AND nuts. Then have people try to put a standard nut on your custom bolt, a standard bolt into your custom nut.
Interesting demo. I think the rationale behind advancing the tool with the compound and the notion that the left edge of the tool is doing all the cutting harks back to the bad old days before insert tooling. Older, hand ground HSS tools were mostly equipped with side rake so the left edge was configured for optimal cutting angles on steel and similar ferrous stock. The right edge will cut but not as well as the left. However your demo clarifies the stepped nature of the cut as it advances. I think most machinists understand this intuitively but probably never see it played out this way.
I'm going to put my 2 cents worth in there...grind the cutter to fit the "V" groove on the threading "arrow-head" and then hold it on your cutting tool and adjust your tool post so that the back side of the arrow head is parallel to the work, and tighten it down. That puts the cutting tool as close to perfect as you can get. Run it slower and never run it out once it's in the cut. Stop the chuck and reverse the direction. (Do a dry run). Take a cut to the end of your run, and then reverse it and go back to taw and take another cut. If it takes another cut, go ahead and take the cut but NEVER disengage the threading gear (saddle drive), because you can never get it exact if you do.
I don't know about doing things with the X & Y electronic help. I learned it "Old School". I was a tool & die maker in the 70's.
Thanks for your video and for bringing old memories to light.
I never leave a threading tool in the thread form and reverse the machine. The backlash could instantly destroy the tool and part. Its OK to leave the halfnut engaged, but retract the tool is my standard practice.
@@joepie221 Exactly my thinking. I have heard people say they should just reverse the lead screw with the tool at depth and I have no idea why they insist on that because for the very reason you mention backlash will ruin the thread.
I never knew how many misconceptions there were in some people's minds around threading on a manual lathe until I watch this video and read the comments🤣