FACT CHECK: Threading Myth BUSTED !! You'll Find This Interesting......
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- Опубліковано 31 сер 2021
- Most machinists have heard the right side of a threading tool does NOT cut with a compound set at 30 degrees. Armchair experts continue to preach this myth. Is this true? Watch this short demonstration and find out. This one is worth watching.
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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.
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!!
:) EVERYTHING can be made more complicated by the internet...
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.
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.
"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 😀
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.
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
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 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 :-)
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.
You’ve done a perfect job of explaining why cutting a staircase thread with a weakened tool would be stupid.
The only people that think the right side of the tool is not cutting have never ran a lathe.
or screw machine ..die heads.
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...
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.
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.
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
Can't believe I missed this when it came out. Well demonstrated and explained, and it makes total sense.
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.
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 👍
This further illustrates the earlier video you did on thread cutting this way. Good job and thanks.
Absolutely superb illustration of a problem I've faced in work many times Joe,& now have the correct ammunition to get my point across.
Cheers for this!👍🏻👍🏻
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 .
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.
Excellent demo to prove a point....Thanks for Sharing....!
Short, sweet and to the point with graphical proof. How simplier can it get. GREAT job Joe, you did it again !!!!!
Awesome content and demonstration...many 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 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.
Never doubted you. Thanks for the look.
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.
Hi Joe! Nice to see you again. All your tips 'n' tricks are most interesting and very helpful! An awesome and very understandable demo. Thanks Joe!
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.
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.
Excellent video and explanation Joe!
Your verbal explanation in a previous video was easy to misunderstand, even though it was 100% correct. This demonstration really helps to clarify the issue. Thanks for taking the time.
It would be interesting to see the same procedure, but with the tool having a small cutting edge on the right side about equal to the compound advancement. Again thanks for the video.
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.
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.
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 !
Always good info! Thanks Joe!.
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.
Greetings, I’m not a machinist but am addicted to your channel. Always good to learn new things, don’t know if I’ll ever use it but it keeps the brain working. Always a good thing 👍
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.
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
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
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’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 🤣
Good stuff Joe! Its actually kind of nice to see it in real time and hear what it sounds like cutting. Sometimes when you speed up the actual milling/turning I wish you would play it in real time so we can get a feel for what good milling/turning should sound like. And if it doesn't sound like that, we would know something is not right.
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
Another great video. Thank you, Professor Pie!
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.
Always learn from you, thank you sir.
Great presentation Joe, as always. Your half tool made me wonder how buttress thread are cut. Is the tool advanced perpendicular to the spindle axis or the compound clocked the opposite as with a 60 degree thread form and incrementally advanced toward the perpendicular flank of the thread with each pass?
Thanks for clarification Joe
thanks for that explanation your videos are always enlightening
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 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.
You show me right before my eyes but my brain needs a bit to catch up.Cheers ta Joe. And respect to you machinist folk.
Joe another good demonstration on thread cutting, I think its a matter of what you are use to doing that is easiest weather it is plunge cutting or compound cutting. The best advise I got from another of your videos was about the threading dial and how to close the half nut.
It would be fun to see you do something like special form threading such as light bulb sockets or buttress threads.
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.
Hi Joe, This was definitely one of the more interesting ones, I am slowly trying to learn and understand the whole turning art, and tool shapes have also been sort of a mystery to me ( I am not a machinist / fitter/turner). This showed quite a lot of things that I did not quite expect or know of before. Thanks again :)
Nice demo Joe, a picture says a thousand words. Thanks j
Thanks Joe. About time someone clarified this. Thanks !!
Always enjoy your videos nice work.
Glad you like them!
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.
Sweet Demo. Seen this topic discussed many times before I even knew what a single point operation even was.
Both sides hold their ground is what I remember most.
This is the way I learned to thread but I don't remember anyone claiming that only one side of the tool was cutting.
You have just demonstated what has always been obvious to me. What I could never understand is why it is not so for everyone !
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.
Very well done and informative. Thanks!
Nice work! Thank you.
Another great piece of pie. Thank you sir. Great info and presentation
Excellent demonstration.
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?
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.
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.
Made sense way before you even went to the effort of the video. The issue of single pointing the angle, similar to my world doing two rail sweeps, never smooth. Question from a total non-machinist (though I have a nice lathe and do a good bit of metal in the shop), I noticed the threading tool and the single sided tool cut dead smooth on the example cuts early in the video, but then the single sided tool chattered heavily on the stepped thread, and the 60 degree tool also chattered a bit? I know this was just for demonstration and the single sided tool likely suffered deflection due to fast feed speed.. but is the 60 degree tool chattering slightly mainly because the leading edge of the tool is doing more work than the trailing edge?
Great demonstration thanks Joe. I’ve had many arguments over this point over the years. This video proves the point (no pun intended) stay safe.
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?!
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.
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.
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
Perfectly demonstrated Joe, thank you!
Good video Joe. Most of the time I plunge straight in 80% of the way in then chase the rest with a die nut.
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.
This whole series on single point threading is phenomenal. I very much appreciate you going to the effort to show what is really happening by removing one side of the tool - the facts are now on show for everyone. I've been cutting threads by just going in straight with the cross slide on my new lathe, but it's got decent rigidity and for small threads the load isn't too much I think. I suspect that as I get to larger threads - 1" and bigger at a guess - the chatter will start to get evident and I'll need to set the compound over. Cheers and best wishes for 2024 (and beyond).
Its always bothered me when I hear someone say the tool doesn't cut on the right side when set at 30 degrees. I figured I'd put that one to rest.
Simply Awesome Joe. Proves that there are those who theorize and then there are those who know. I guess at the time I posted my comment there were 13 theorists who didn't like having their theory busted by your great demonstration. Thanks for sharing Joe. Thumbs Up! Best Wishes & Blessings. Keith Noneya
Great observations and demo. Enough said.
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.
Great video. I do have a question:
I'm not a machinist so excuse me if its an ignorant question.
Couldn't you just go in reverse with the tool to clean up the ragged edges? Or is the operation only one way, or perhaps too unsafe?
Also, is the control depth movement done by hand with a scale reference, or is it automatic? I don't see the whole machine in the video.
CNC lathes (Siemens 840d control, ShopTurn) offer an alternating left/right cutting cycle for threading for better wear and finer threads.
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.
Great demonstration Joe, I was taught this in my apprenticeship but have run into many people who hold the view of single edge cutting. Cheers, Jon
Throw some layout die on the part between passes and that should shut up the wizzards. If you do the 29-1/2 like the old South Bend book shows and if you got the tool ground perfectly there will be zero point no layout die on both flanks in each and every pass and both flanks will have no steps and be smooth as babies ,,,,,,,,,,,,
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.
Good Morning Joe.....best wishes, from Florida, Paul
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.
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.
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.
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.
Great demo