I used to work with an old millwrght - he showed me the tricks - he said before we started that the steel would draw back one half as much as the heat moved it. After determining where the bend was we moved the indicator to the end of the shaft - we heated the shaft until the end of the shaft moved nearly 1.5 times the runout and removed the heat. His system worked like a charm.. he said to always pull the heat before you reached the 1.5 target. Once the shafts start moving they have some inertia from the heat. Then when things cool down you can make what he called a trim adjustment.. he was a genius - he was a master at balancing rotating machinery and alignments ... we could align machinery with a hand full of indicators some feeler guages a sledgehammer and a slugging wrench before the "smart guys" could set up their $80,000.00 electronic infrared alignment tool. And ours wouldn't shake. I know this video is old but maybe someone will get some good out of it... it seems all the kids want a computer to tell them what to do instead of actually knowing the basics of what they should be doing... I'm 71 years old and still doing consulting on machinery alignment. It's a sign the young guys did not learn their trade -
wow lol I have been working on straitening a box I welded up for something a while back. The welds are horribly undercut and its too rusty now to use, but I have been working on heat striatening using a resistive heater. I hooked up a brazing transformer to a 600 amp welding clamp (the ones for lathes) and then I brazed a 1/2 inch copper rod into a 4/0 lug and connected it with 4/0 to the transformer studs (its a box meant for those big carbon soldering pliers). If you touch the sheet metal with the rod it starts buzzing and you get a hot spot the size of a dime in a few seconds on 10 gauge. I was practicing hitting it with a hammer and different patterns etc. Dip it in a cup of water once in a while to cool the electrode. Really interesting setup (about 5V OCV, floating, at 1500ish amps). I just wanna make some kinda handle piece and put some teflon heat shrink on the rod etc to insulate it a little bit. Very fun. Just if you get those ancient boxes they need a bit of work.. I added vents, and some wire supports with ETFE heat resistant zip ties to neaten up the wiring, itts built a little scary (looks like if the transformer really failed hard the primary insulation could touch the secondary, so you need to megger it too, 1940 is not that great a electrical safety! Going to add some fiberglass silicone sleeves on the primary wiring too just incase.. but honestly it runs pretty damn cool considering all thats going on there. Nice technology with no O/A fumes and soot.
I know absolutely nothing about machining metal but I can learn by watching you. You do a great job of narration and your explanations are simple but make sense. I'm an old fart but I still love to learn new things and you do a super job of teaching. Thanks for sharing your talents. Laff in OKC, Ok.
ml7898 Thanks Laff - I too am slowly becoming one of those "old farts" myself! So happy that you are enjoying the site and learning something along the way!
Amazing. My summers were spent working on my Aunt' and Uncle's Farm Character building as we lived in Chicago my father said. Their machine shop looked much like yours as I remember it from the 60's and 70's. I learned how to flame straighten all kinds of drive, cutter, auger, etc... shafts exactly as you showed it. Thank you for the trip back to my roots. I'll be spending the rest of the night watching the rest of your videos as I see some very familiar equipment and techniques.
Ed Andrews Thanks Ed - there is nothing like working on a farm to build the character of a young person. I know that experience had a huge impact on me! Glad that you are enjoying the videos!
Keith Fenner uses compressed air to cool the shaft. It may need to be chilled from the red. However your method works just fine. I am going to see if I can straighten the spindle on my drill press, it would be nice to get rid of the wobble. Thanks for your tireless hours making these videos. :)
Provided that the cutter flanks are square to the bore, they will probably pull most of the .007" out when the nut is tightened. A very interesting video. I like the way that you sampled the full length first. Nothing more frustrating then to straighten one section first only to find the main bend was somewhere else. I used to straighten launch shafts. Some of them could be literally curly after striking a sand bank at speed.
Excellent video Keith! I have always been curious about flame straightening shafts and most people don't want to share their secrets. Very informative and helpful, thank you for sharing this with us. Regards, Bill
A very measured approach and well thought out Keith. I enjoyed seeing how you went about the process. Keith Fenner did at least one if not two videos on straightening propeller shafts. They were also very informative. Thank you! Fred
Great video Keith. I had the thought while watching about having the indicator on the end while heating to see just how much it moves..... second camera and split screen would be simply awesome!! Thanks for sharing! Colin
Very nice. My grandfather was an engineer on the Union Pacific's main line. Drove a FEF from Council Bluffs to North Platte. It started as a coal engine but was converted to oil about the start of WW2.
Very informative video, thank you. One suggestion though...most people watch videos from start to finish and if something is missed or misunderstood, we can hit the replay button. I'm sharing this with you so that in future videos you won't have to verbally repeat what you are doing every five seconds and the videos would be a LOT shorter : ) No offense intended : )
A number of years ago I was fortunate to be able to attend a living history demonstration at Bridge Park near Battle Creek, MI. The presenters straightened two foot high sections of bridge support I beams by heating the flanges in a variation of the method you used. While they were working they gave a running description of the methods used and their effect on the beam. They mentioned how much damage a semi hauling too high a load can cause to a bridge beam.
Another great video. I have used heat for straightening on various things myself. It is amazing how well it works. I also used to straighten motorcycle fork tubes with my hydraulic press. I made some wide "C" shaped tools to press down on the fork tubes and also to support the ends. I could get them within ten thousandths most of the time.
At shipyards they use the same technique for bending steelplates in irregular patterns , for example at the bow-nose and the portions of hull under the waterline where the bending radius changes over the length. At the shipyards it is completely made by hand and blowtorch.
Hi Keith, Great job and video. I have only one suggestion.... When you quench the piece start by cooling the OPPOSITE side from the side you heated. It's the longer side of the bend and what you're trying to do is shorten it and lengthen the heated or shorter side. It will make the job go more quickly and you'll use less gas.:) Dick ( the blacksmith )
Keith, Take a piece of 1/2" square and hold it in a vise horizontally with about 2' sticking out. When you play the torch against one side you'll see the end of the bar move. If you cool the opposite side with a wet rag, you'll see that you can freeze part of that bend ( movement) in or even pull more in the direction of the movement. Hope this helps, Dick
Dick Sargent you are 100% correct. I apprenticed under a Swiss Master machinist. He taught me much about expanding and shrinking steel. Heating one side and cooling the opposite side attains the desired result much quicker and with less chance of damage to the metallurgical structure of the steel.
I've straightened many bent axle housings this way. Heat one side, cool the opposite. As an auto technician for 21 years some of my customers are construction workers and their vehicles see severe terrain and conditions loaded with supplies/equipment and bend the axle tubes. This is just one more reason why I suggest a thrust alignment for solid axles or a 4 wheel alignment for independent, over just a simple front end alignment.
Keith nice job on the spindle looks like you were able to save it. Good to see your take on flame straightening. Good tips on setting the zero on your dial indicator too.
Nice job Keith. Knowing the trick to flame straightening saves a lot of time & money for you & your customer. It's a great solution if you can get it right, and I think your slow and easy approach is the way to go. Thank's for another great vid. Cheer's from Canada !
Great video, I need to do this to a brake lathe spindle and this told me exactly what I wanted to know about how to accomplish my goal. It looks very similar to the part your working with, and its out 0.028 at the end. So I think I should be able to get it dead on.
Keith , there is a guy here who uses heat to straighten custom drive shafts----the tircks as I understand it is to heat it up ---put a indicator on the end to check alignment ---spin chuck by hand and use a wet rag and COOL the side you want to draw ----slowly spinning the chuck as you go ----when the low comes up--put wet rag there. Also in earlier video where you received round carbide disks---they are button tool inserts for forming radius on lathes --also we use them to rough out extremely uneven lathe work surfaces (flames cuts and etc.) . The inserts are much tougher than regular inserts --and even when they do chip , you can slightly turn them in the holder and gain a new cutting edge. great job---jdb21867---journeyman of 37 years --age 57.
Keith, Good job. I've done thousands of shafts, ejector pin and mandrels. What i've found works best is slightly heat the area of bend and with a 2x4x? us as leverage to make straight. This action will anti-bend. Sometimes you have to flip the shaft .. even several times to make straight. and sometime heat will just mess you up. depends on the shaft, the size, thickness, area of bend and thickness. (Many factors determine the action fix) Of course heat treated shafts are a whole new kettle of fish. Being mindful of DeTempering and even reheatreating will put the bend right back in it. A whole new method of heat treatment requires it to free hang during initial heat treatment and draw back. But good job just the same. What i'm talking about requires much more intuition and effort.
Nice video Keith. My understanding of the process is that when the part is heated to red heat and then quenched the outside of the metal quickly cools to stabilise the metal on the outside making it rigid while the inside is still in a plastic state. Due to the metal being cooled on the outside first, the metal cools slower on the inside while holding it's shape. Some internal stresses are present but not enough to worry about. Welding is different because you are introducing more metal to the part which cools quickly and pulls the parent metal towards the weld but also introduces a heat affected zone around the weld that crystalises the parent metal due to the rapid cooling. This is why you would heat the weld or parent metal before or after to normalise it to relieve the internal stresses if you had a critical part. Just my two cents worth. Interesting discussion. :-)
Bill Lewis the way the shaft is bent, it's bent towards the high side, heating that side near the base makes that side grow a little longer therefore pushing the other end back where it needs to go. Putting water on to cool quickly helps "freeze"it where it is. If he'd let it just cool it probably would be back where he started
Bill Lewis Hi Bill, Its almost purely mechanical in nature. Its an upset. The rapid heating pushes against the surrounding cooler material and forms a small upset. The net change is a shorter section right where the material was heated. It acts just like a tiny turnbuckle pulling the material up. I have a chapter dedicated to the process in my books if you want to learn more. Welding does the same thing. As the hot weld cools it shrinks causing the same turnbuckle effect. All the best, Tom
oxtoolco Tom- I have the same question as Bill. I replayed a couple times and if I understood Keith's indicator, in this case the work moved the _opposite_ way; that is, the hot spot didn't shrink, it grew. Conventionally the heated spot (or weld bead) should freeze under tension and shrink. ??? -mike
I'm surprised at how this worked. In a prior life I was a structural steel welder/fabricator and did lots of heat straitening (up to 60ft long beams). Our practice was and my experience still is ( I work with sheet metal now) that the shrinking/cooling effect is more powerful than the expansion/heating. I always heat the OUTSIDE of the bend. Adding water or compressed air to cool increased the effect. Does a solid shaft react opposite of a structural/hollow member? I'm totally confused at how/why this worked for you Keith.
76RSLT Hi 76, The net result of the application of the heat is a shrink. So you are correct that the high spot or outside of the bend it heated and cooled. Initially there is an increase in the bend but on cooling the net is a shrink. Its behaves just like welding. Cheers, Tom
That's pretty dang slick, i didn't know the metal would react that way by just heating it. I am taking notes this is very interesting info. Thank you Sir for sharing.
Hi Keith, Very good video with the cone theory and how to determine the kind of bend, now I feel I can try it with confidence if needed. Thanks again for giving us yourself and your time. Pierre
Excellent explanation, another tip for smaller shafts is to use a tig torch. It heats a much smaller area and is easier to control. Really enjoy your videos!
Well done. It surprises me that the axle doesn't bend back when getting cold down. The first job for my mini lathe was straightening a 2 feet long, 1/2" candle stick being bent to a shape like a cork screw. It was painted as well... Masking tape for protection, the cross slide and the tool post was used to press it, once every 2". It worked out well.
I am not a machinist but I love to watch you work. What you did was fascinating and elegant. I suspect that if you took the data points you gathered and plotted them on graph paper you would get a picture of where the bend really is. For the x axis, use the distance along the shaft from some reference point, like the bottom flange. It won’t matter where you pick the reference, as long as you are consistent. For the y axis of each data point, use the high value you measured with the indicator. For a single bend or misalignment, you should find the points are all on a straight line. Where this line crosses y=0 is the source of the problem. Just estimating in my head, I suspect that the real problem is that the spindle threads to the motor shaft are the source of the misalignment. In such a case, you chose exactly the right point to apply heat, although you will always have a 6 thou runout.
Hey Keith, Great video! I just learned something else I can put in my "Bail-Your-Nuts-Out-of-the-Fire" file. Thanks for sharing your knowledge and experience with us novices! Regards, Dave
Learned this as a apprentice panel beater we called it heat shrinking when the panel was stretched we would put a 5 mm hot spot then quench it the spot would shrink tightening the panel up .
Huh. Your elegant approach there worked surprisingly well, I've learnt something new as I wouldn't have expected much to happen by applying heat alone... In my mind I thought you would need both heat AND force in the opposite direction to the bend to get the result. Anyways, many thanks for showing us how it's done!
I have had good luck with my homemade tool. It’s like a knurling tool but I have smooth bearings and I use a live center. Using heat and the homemade tool I have had surprisingly good results. It saved from having to spend 800 dollars on a cross feed screw.
Keith, Great video. I have flame straightened quite a bit of steel. I was taught that you want to use counter pressure as well as heat to speed things up. Also if you are flame straightening square stock you want to use the counter pressure to insure a proper bend and not have your work twist as it cools. This is not as critical on round stock but it is very critical on c channel, square tubing and H or I beam. On square stock you use a V shape heat pattern where the Top of the V is the area you are wanting to shrink. You begin the cooling process at the bottom of the V and move upward.
I agree with you, counter pressure can provide better control over the response of the item to heating and cooling. I have worked in the construction industry. We have straightened out deformed structural members by loading the element with hydraulic rams or chain come alongs while applying heat. This works well when building up large plate girders on site.
Great video, Keith. I plan to try this on a shaft from a Gravely mower deck soon. One question/suggestion. It seems to me that it would be very handy to keep the indicator on the part (far from the flame obviously) so that you could observe the movement as you heat and cool. In the case of your part, you could put the indicator at the far end and you should observe a lot of movement.
If you do this, you will see the indicator move in the WRONG direction (ie, increasing the bend) as you apply the heat. The usual practice is to keep the heat on until the wrong-way movement is about three times the desired right-way shrinkage.
There was something sold for Copper pipe work that you would use as a between the copper pipe and the wood frame it like a 1/2 in thick and 8 x 12 used a shield for the wood (made out of some type of cloth material). Hardware stores have them in the pluming section. It does a good job of keeping heat away when you have to sweat copper in a wall.
Cool video. I Didn't even know that heat straightening was a thing until now. When you were polishing the shaft at the end of the video it was interesting that the lathe took quite a while to get up to full speed. Sounded somewhat like a turbine.
Thanks for sharing Keith... I have an ACME threaded lathe compound screw with a slight "S" bend in it that I think should benefit from this straightening technique. I was just going to machine a new one so got nothing to lose by trying this...
a few years ago union pacific flame straightened a bridge near my house. it is 97 years old now and still carrying up to 20 main trains per day....2 men worked for 2 weeks with rosebuds heating the bottoms of I beams...the bridge amounts to a bunch of beams laid on top of concrete buttress, covered with wood and gravel, it would be interesting to lay that aside for a few weeks then remeasure it to see if it changes with time
Nicely done sir! I need to straighten a bent drill press spindle, that I can’t buy a replacement part. I have no Lathe, no oxy - acetylene torch, and no run out dial indicator, so with just a vice & butane torch & straight edge, I’m guessing I’ll have to employ a hardwood 2 x 4 & some leverage & wing it and see how I go! Still handy to see the principle at work by an expert.
Don't let people get under your skin by questioning your decisions. I would just tell them "Thanks for the feedback but It's my shop, my lathe, and my job. You can do it any way you want." For example, in steel construction, we don't heat the steel so hot but we apply considerable force to coax a structural member into the desired position. But those are very different grades of steel from steel shafting with very different loading patterns.
Someone else may already have suggested this, but I reckon a handy addition to a dial indicator is an "elephant's foot", basically a large diameter thin cylinder (like a coin only smaller, with a screwed extension) which fits in place of the usual ball-ended tip, enabling clocking up over a thread, keyway, tips of gear teeth, or whatever, without the tip descending into the valleys. You can make them, or buy them.
In the last few years I've learned a lot about heat straightening, since watching a couple of youTube videos on the underlying mechanism from the superb channel "An Engineer's Findings". every thing I've attempted since then has worked, plus I now have an understanding of weld distortion, something which had eluded and frustrated me previously. I've only watched to 12:10 so far, but I'm going out on a limb to say that reheating that first spot is not likely to produce much further action. I can see why Keith chose to do that, because there's no point trying elsewhere because that's clearly where the bend is concentrated. I perhaps would have tried the face immediately beside (to the left of) the spot he heated. If that helped but more was needed, I'd try a could of shrinks immediately adjacent to the first one and on the same cylindrical surface, one each side, at the same distance from the face referred to above. So now I'm going to watch what really happened as opposed to what I think will happen.
So yes, reheating the first spot didn't do it. Keith actually tried something I considered and discarded, which was to heat further away from the face. I realised that would reduce the runout at the end of the shaft (which it did) but I felt it would leave the shaft slightly bent, like a question mark which had been almost straightened out but not quite. In other words, the left and right ends of the shaft would be true, but not the middle. (Another way of describing it would be a skipping rope)
Always thought that you drew metal using heat and cold. (the side that you wanted the metal to travel, would be where you put the heat) We would use the dial indicators several places and get the reference points, like you did. We would draw 12 to 18 ft. x 4" agitator shafts back into spec, but we would put the heat on the side, the way we wanted it to draw, then cool it with ice and sometimes co2. The heat caused it to expand, then the cold drew it back past were it was before applying the heat.
I see comments throwing words like "temper" and "quenching" around. Keith didn't wet it down from anywhere near critical temp, but for some steels the localized heat will make the rest of the spindle act as enough of a heat sink to cause problems. Whatever steel it is, a little or alot of stress is introduced. For this high speed use a stress relief at 5-600 C could be a good idea, and I'd be interested to see if that interferred with the "set" gained by straightening.
Sometimes, after a treatment like that you can “ring” it sharply with a steel hammer to relieve the stress and the runout will change slightly. Doesn’t hurt to check it again.
Keith, I'm wondering how you could check to make sure the spindle is straight on the arbor? For example, if you had a burr or a highspot on the area which the spindle registers on the arbor.
From 15:45 to 16:10 it sounds like your lathe is picking up speed?? Is that even possible? Thought it was a geared head? Makes me want to get the tach out now.
The only thing I was thinking was if the lathe was wired 480V but was being fed 240V power. Under big loads like running high gear I have seen this same thing where it takes a bit to get to full speed because of the lower voltage. Probably just dopler effect from mic position though like you said.
I heard this also on the last video where he turned and threaded the 3/4" spindle, in the same situation where he geared the speed up for polishing. My guess is that the motor is struggling a little to spin up that massive 4-jaw chuck. In higher gears, the motor provides more speed and less power, so it takes more time to accelerate to the speed specified on the motor. Yes, a geared head means that the chuck is turning at a fixed ratio relative to the motor speed....but the motor speed can vary depending on load, and a high gear places a larger load on the motor. The doppler effect will be insignificant at the speeds that Keith is moving around the lathe, so that's certainly not the explanation.
i used to straighten 40' and 60' trailers by putting heat in to the neck of the trailer similar sort of thing but on a bigger scale use to put the heat in the shape of a v
I thought that when you heated the metal red hot and quenched it the spot would shrink, causing the bend to be worse. Instead, heating and quenching froze the metal in the expanded condition, correcting the bend. I see I was wrong in my analysis so I learned a lot from this video.
In the exchanges between Bill Lewis and Tom Lipton, I noticed that Tom interpreted Keith's referring to the side with the higher indicator reading as the "high side" or "high spot" of the bend. I prefer concave or convex, and don't see how heating, then cooling, on the concave side got the result that it did - and I've read Tom's book, with particular attention to this chapter.
Very informative and your skill level is obvious. One suggestion - tell us something 1 time! eg.: several times you informed us you were not an expert - got it.
I know it’s been years since this was done but this process was in reverse. The correct way to straighten with a flame on a solid bar is to put the low end down and heat the opposite end top. And do not use coolant. This video shows the opposite working. Baffling. But I think I know why. If you try to straighten a tube or hollow section you use this method as shown in this video. If you look when he removes the shaft to show you the threaded section it looks as though there is a certain amount of counterbore which in effect makes this a solid bar at one end and a hollow bar at the other. Therefore he is actually straightening a hollow section. I worked in a reclaimation engineers shop on a large dock using this process to straighten shafts up to 6” diameter up to 10 feet long. And hollow sections too. It could take all day to straighten a shaft as you had to wait for the shaft to cool. I have seen comments stating this process is the opposite of what most people do. Jeff
Most likely that part wasn't bent in the shaft. the way its built is essentially two cylinders joined by a plane. The plane (where it sits flat on the end of the spindle) is probably where it deformed. After getting it straight, it probably would have been best to face the mounting surface off on the inside, but that probably would have been overkill. Either way, you did salvage a damaged part.
11:46 Do you have any idea if you can do this with a MAP gas torch? Also do you think you have to get it red hot inorder for it to permanently bend? The reason I ask is I have a bent spindle that I'm thinking of straightening like this but I'm worried about affecting the heat treatment of the splined shaft. Plus I REALLY REALLY REALLY don't want to (or even have the means to) remake the splined spindle with a MT2 on one end.
Seems to me tho that in doing this aren't you tempering out any of the hardening that has been put into this shaft. Is that an issue or are we to assum it had no hardening to begin with. If that's the case do you still get the straw thru purple colors when heating campletely annealed steel? I haven't done enough metalwork to know all the details like this yet as I've only just started into smithing casting and machining.
It might be worth having a word with Keith Fenner about this proccess. He cools the hot spot very rapidly and I suspect this might give a sharper response to the bend you create. Maybe you would be able to reduce this run out even more. By the way was that a proper engineers sponge or just a regular household type?
14:57 @AvE would appreciate that diss to woodworking. I totally get it though and it's something I struggle with myself going from metalworking to woodworking-that is the completely different dimensional stability between their materials.
I've never done this before but when you cool the metal, would it have more of an effect if you just touch the sponge to the side opposite the heated spot?
Many thanks, that's been most interesting and informative. Is there any reason why this technique could not be used with shapes of shaft e.g. square, rectangular or even angle iron?
Best plan-first try to straighten the spindle- if successful great- if not turn it down to make the 3/4 one, then use your material to make a new 1.25 unit.
I used to work with an old millwrght - he showed me the tricks - he said before we started that the steel would draw back one half as much as the heat moved it. After determining where the bend was we moved the indicator to the end of the shaft - we heated the shaft until the end of the shaft moved nearly 1.5 times the runout and removed the heat. His system worked like a charm.. he said to always pull the heat before you reached the 1.5 target. Once the shafts start moving they have some inertia from the heat. Then when things cool down you can make what he called a trim adjustment.. he was a genius - he was a master at balancing rotating machinery and alignments ... we could align machinery with a hand full of indicators some feeler guages a sledgehammer and a slugging wrench before the "smart guys" could set up their $80,000.00 electronic infrared alignment tool. And ours wouldn't shake. I know this video is old but maybe someone will get some good out of it... it seems all the kids want a computer to tell them what to do instead of actually knowing the basics of what they should be doing... I'm 71 years old and still doing consulting on machinery alignment. It's a sign the young guys did not learn their trade -
wow lol I have been working on straitening a box I welded up for something a while back. The welds are horribly undercut and its too rusty now to use, but I have been working on heat striatening using a resistive heater. I hooked up a brazing transformer to a 600 amp welding clamp (the ones for lathes) and then I brazed a 1/2 inch copper rod into a 4/0 lug and connected it with 4/0 to the transformer studs (its a box meant for those big carbon soldering pliers). If you touch the sheet metal with the rod it starts buzzing and you get a hot spot the size of a dime in a few seconds on 10 gauge. I was practicing hitting it with a hammer and different patterns etc. Dip it in a cup of water once in a while to cool the electrode. Really interesting setup (about 5V OCV, floating, at 1500ish amps). I just wanna make some kinda handle piece and put some teflon heat shrink on the rod etc to insulate it a little bit. Very fun. Just if you get those ancient boxes they need a bit of work.. I added vents, and some wire supports with ETFE heat resistant zip ties to neaten up the wiring, itts built a little scary (looks like if the transformer really failed hard the primary insulation could touch the secondary, so you need to megger it too, 1940 is not that great a electrical safety! Going to add some fiberglass silicone sleeves on the primary wiring too just incase.. but honestly it runs pretty damn cool considering all thats going on there. Nice technology with no O/A fumes and soot.
This is super helpfull. Rebuilding the spindle of my surface grinder. Thanks!!!
Keith, this is the best description of heat straightening I have found. You sir are an outstanding craftsman. Thank you sir.
I know absolutely nothing about machining metal but I can learn by watching you. You do a great job of narration and your explanations are simple but make sense. I'm an old fart but I still love to learn new things and you do a super job of teaching. Thanks for sharing your talents. Laff in OKC, Ok.
ml7898 Thanks Laff - I too am slowly becoming one of those "old farts" myself! So happy that you are enjoying the site and learning something along the way!
Amazing. My summers were spent working on my Aunt' and Uncle's Farm Character building as we lived in Chicago my father said. Their machine shop looked much like yours as I remember it from the 60's and 70's. I learned how to flame straighten all kinds of drive, cutter, auger, etc... shafts exactly as you showed it. Thank you for the trip back to my roots. I'll be spending the rest of the night watching the rest of your videos as I see some very familiar equipment and techniques.
Ed Andrews Thanks Ed - there is nothing like working on a farm to build the character of a young person. I know that experience had a huge impact on me! Glad that you are enjoying the videos!
Awesome job Keith!! That spindle looks as good as new. Thank you for sharing with us!
Adam
Great video
Keith Fenner uses compressed air to cool the shaft. It may need to be chilled from the red.
However your method works just fine. I am going to see if I can straighten the spindle on my drill press, it would be nice to get rid of the wobble.
Thanks for your tireless hours making these videos. :)
Provided that the cutter flanks are square to the bore, they will probably pull most of the .007" out when the nut is tightened. A very interesting video. I like the way that you sampled the full length first. Nothing more frustrating then to straighten one section first only to find the main bend was somewhere else. I used to straighten launch shafts. Some of them could be literally curly after striking a sand bank at speed.
Excellent video Keith! I have always been curious about flame straightening shafts and most people don't want to share their secrets. Very informative and helpful, thank you for sharing this with us.
Regards, Bill
A very measured approach and well thought out Keith. I enjoyed seeing how you went about the process. Keith Fenner did at least one if not two videos on straightening propeller shafts. They were also very informative. Thank you! Fred
Great video Keith. I had the thought while watching about having the indicator on the end while heating to see just how much it moves..... second camera and split screen would be simply awesome!!
Thanks for sharing!
Colin
Very nice. My grandfather was an engineer on the Union Pacific's main line. Drove a FEF from Council Bluffs to North Platte. It started as a coal engine but was converted to oil about the start of WW2.
Very informative video, thank you. One suggestion though...most people watch videos from start to finish and if something is missed or misunderstood, we can hit the replay button. I'm sharing this with you so that in future videos you won't have to verbally repeat what you are doing every five seconds and the videos would be a LOT shorter : ) No offense intended : )
Excellent video. You are among the best in the machining industry.
A number of years ago I was fortunate to be able to attend a living history demonstration at Bridge Park near Battle Creek, MI. The presenters straightened two foot high sections of bridge support I beams by heating the flanges in a variation of the method you used. While they were working they gave a running description of the methods used and their effect on the beam. They mentioned how much damage a semi hauling too high a load can cause to a bridge beam.
+Old Sneelock's Workshop I saw a UA-cam video showing straightening a bridge beam. Pretty impressive!
Another great video. I have used heat for straightening on various things myself. It is amazing how well it works. I also used to straighten motorcycle fork tubes with my hydraulic press. I made some wide "C" shaped tools to press down on the fork tubes and also to support the ends. I could get them within ten thousandths most of the time.
excellent idea for straightening the fork tubes
At shipyards they use the same technique for bending steelplates in irregular patterns , for example at the bow-nose and the portions of hull under the waterline where the bending radius changes over the length. At the shipyards it is completely made by hand and blowtorch.
Hi Keith, Great job and video. I have only one suggestion.... When you quench the piece start by cooling the OPPOSITE side from the side you heated. It's the longer side of the bend and what you're trying to do is shorten it and lengthen the heated or shorter side. It will make the job go more quickly and you'll use less gas.:)
Dick ( the blacksmith )
Keith,
Take a piece of 1/2" square and hold it in a vise horizontally with about 2' sticking out.
When you play the torch against one side you'll see the end of the bar move. If you cool the opposite side with a wet rag, you'll see that you can freeze part of that bend ( movement) in or even pull more in the direction of the movement.
Hope this helps,
Dick
Dick Sargent
you are 100% correct. I apprenticed under a Swiss Master machinist. He taught me much about expanding and shrinking steel. Heating one side and cooling the opposite side attains the desired result much quicker and with less chance of damage to the metallurgical structure of the steel.
I've straightened many bent axle housings this way. Heat one side, cool the opposite. As an auto technician for 21 years some of my customers are construction workers and their vehicles see severe terrain and conditions loaded with supplies/equipment and bend the axle tubes. This is just one more reason why I suggest a thrust alignment for solid axles or a 4 wheel alignment for independent, over just a simple front end alignment.
Hi Keith !
Nice to see how straightning is done with a torch - thx for sharing !
Keith nice job on the spindle looks like you were able to save it. Good to see your take on flame straightening. Good tips on setting the zero on your dial indicator too.
That's the way to learn and get experience, by trial and error and to see other do it. That's my way of learning anyway. Thanks for sharing.
Nice job Keith. Knowing the trick to flame straightening saves a lot of time & money for you & your customer. It's a great solution if you can get it right, and I think your slow and easy approach is the way to go. Thank's for another great vid. Cheer's from Canada !
Nice job Keith , we use to start the cooling on the opposite side like the other gentleman stated. Thanks for all your videos
Great video, I need to do this to a brake lathe spindle and this told me exactly what I wanted to know about how to accomplish my goal. It looks very similar to the part your working with, and its out 0.028 at the end. So I think I should be able to get it dead on.
Keith , there is a guy here who uses heat to straighten custom drive shafts----the tircks as I understand it is to heat it up ---put a indicator on the end to check alignment ---spin chuck by hand and use a wet rag and COOL the side you want to draw ----slowly spinning the chuck as you go ----when the low comes up--put wet rag there.
Also in earlier video where you received round carbide disks---they are button tool inserts for forming radius on lathes --also we use them to rough out extremely uneven lathe work surfaces (flames cuts and etc.) . The inserts are much tougher than regular inserts --and even when they do chip , you can slightly turn them in the holder and gain a new cutting edge. great job---jdb21867---journeyman of 37 years --age 57.
Keith, Good job. I've done thousands of shafts, ejector pin and mandrels.
What i've found works best is slightly heat the area of bend and with a 2x4x? us as leverage to make straight. This action will anti-bend.
Sometimes you have to flip the shaft .. even several times to make straight. and sometime heat will just mess you up. depends on the shaft, the size, thickness, area of bend and thickness. (Many factors determine the action fix)
Of course heat treated shafts are a whole new kettle of fish. Being mindful of DeTempering and even reheatreating will put the bend right back in it. A whole new method of heat treatment requires it to free hang during initial heat treatment and draw back.
But good job just the same. What i'm talking about requires much more intuition and effort.
Nice job on the straighting of the arbor. One of those thing you don't until you try it. Great video again. Thank you.
Nice video Keith.
My understanding of the process is that when the part is heated to red heat and then quenched the outside of the metal quickly cools to stabilise the metal on the outside making it rigid while the inside is still in a plastic state. Due to the metal being cooled on the outside first, the metal cools slower on the inside while holding it's shape. Some internal stresses are present but not enough to worry about.
Welding is different because you are introducing more metal to the part which cools quickly and pulls the parent metal towards the weld but also introduces a heat affected zone around the weld that crystalises the parent metal due to the rapid cooling. This is why you would heat the weld or parent metal before or after to normalise it to relieve the internal stresses if you had a critical part.
Just my two cents worth.
Interesting discussion. :-)
Hey Keith,
Nice video. You got the technique right. The arbor was a great example for the process.
All the best,
Tom
Bill Lewis the way the shaft is bent, it's bent towards the high side, heating that side near the base makes that side grow a little longer therefore pushing the other end back where it needs to go. Putting water on to cool quickly helps "freeze"it where it is. If he'd let it just cool it probably would be back where he started
Bill Lewis Hi Bill,
Its almost purely mechanical in nature. Its an upset. The rapid heating pushes against the surrounding cooler material and forms a small upset. The net change is a shorter section right where the material was heated. It acts just like a tiny turnbuckle pulling the material up. I have a chapter dedicated to the process in my books if you want to learn more. Welding does the same thing. As the hot weld cools it shrinks causing the same turnbuckle effect.
All the best,
Tom
oxtoolco Tom- I have the same question as Bill. I replayed a couple times and if I understood Keith's indicator, in this case the work moved the _opposite_ way; that is, the hot spot didn't shrink, it grew. Conventionally the heated spot (or weld bead) should freeze under tension and shrink.
???
-mike
I'm surprised at how this worked. In a prior life I was a structural steel welder/fabricator and did lots of heat straitening (up to 60ft long beams). Our practice was and my experience still is ( I work with sheet metal now) that the shrinking/cooling effect is more powerful than the expansion/heating. I always heat the OUTSIDE of the bend. Adding water or compressed air to cool increased the effect. Does a solid shaft react opposite of a structural/hollow member? I'm totally confused at how/why this worked for you Keith.
76RSLT Hi 76,
The net result of the application of the heat is a shrink. So you are correct that the high spot or outside of the bend it heated and cooled. Initially there is an increase in the bend but on cooling the net is a shrink. Its behaves just like welding.
Cheers,
Tom
That's pretty dang slick, i didn't know the metal would react that way by just heating it. I am taking notes this is very interesting info. Thank you Sir for sharing.
Hi Keith,
Very good video with the cone theory and how to determine the kind of bend, now I feel I can try it with confidence if needed.
Thanks again for giving us yourself and your time.
Pierre
Excellent explanation, another tip for smaller shafts is to use a tig torch. It heats a much smaller area and is easier to control. Really enjoy your videos!
Well done. It surprises me that the axle doesn't bend back when getting cold down.
The first job for my mini lathe was straightening a 2 feet long, 1/2" candle stick being bent to a shape like a cork screw. It was painted as well...
Masking tape for protection, the cross slide and the tool post was used to press it, once every 2". It worked out well.
Very good tutorial of heat straightening! Thanks for sharing Keith.
I am not a machinist but I love to watch you work. What you did was fascinating and elegant. I suspect that if you took the data points you gathered and plotted them on graph paper you would get a picture of where the bend really is. For the x axis, use the distance along the shaft from some reference point, like the bottom flange. It won’t matter where you pick the reference, as long as you are consistent. For the y axis of each data point, use the high value you measured with the indicator. For a single bend or misalignment, you should find the points are all on a straight line. Where this line crosses y=0 is the source of the problem. Just estimating in my head, I suspect that the real problem is that the spindle threads to the motor shaft are the source of the misalignment. In such a case, you chose exactly the right point to apply heat, although you will always have a 6 thou runout.
Hey Keith,
Great video! I just learned something else I can put in my "Bail-Your-Nuts-Out-of-the-Fire" file. Thanks for sharing your knowledge and experience with us novices!
Regards,
Dave
Learned this as a apprentice panel beater we called it heat shrinking when the panel was stretched we would put a 5 mm hot spot then quench it the spot would shrink tightening the panel up .
Huh. Your elegant approach there worked surprisingly well, I've learnt something new as I wouldn't have expected much to happen by applying heat alone... In my mind I thought you would need both heat AND force in the opposite direction to the bend to get the result. Anyways, many thanks for showing us how it's done!
Keith, you are the greatest. Your explanations are perfect. Please keep the videos coming.
Thank you - please keep watching!
GREAT job keith ,keep the videos coming from a old woodturner.
I really appreciate your videos. they are very informative. thank you for taking the time to share your knowledge with us.
Learn something new every day, thanks for today's lesson Keith
Wow excellent work! Man I have been itching to see a video on this for a couple of years now THANKS!
I have had good luck with my homemade tool. It’s like a knurling tool but I have smooth bearings and I use a live center. Using heat and the homemade tool I have had surprisingly good results. It saved from having to spend 800 dollars on a cross feed screw.
Keith, Great video. I have flame straightened quite a bit of steel. I was taught that you want to use counter pressure as well as heat to speed things up. Also if you are flame straightening square stock you want to use the counter pressure to insure a proper bend and not have your work twist as it cools. This is not as critical on round stock but it is very critical on c channel, square tubing and H or I beam. On square stock you use a V shape heat pattern where the Top of the V is the area you are wanting to shrink. You begin the cooling process at the bottom of the V and move upward.
+Scott Young Thanks for the tips!
I agree with you, counter pressure can provide better control over the response of the item to heating and cooling. I have worked in the construction industry. We have straightened out deformed structural members by loading the element with hydraulic rams or chain come alongs while applying heat. This works well when building up large plate girders on site.
or you use a diamond shape its called diamond heating.
Great video, Keith. I plan to try this on a shaft from a Gravely mower deck soon.
One question/suggestion. It seems to me that it would be very handy to keep the indicator on the part (far from the flame obviously) so that you could observe the movement as you heat and cool. In the case of your part, you could put the indicator at the far end and you should observe a lot of movement.
If you do this, you will see the indicator move in the WRONG direction (ie, increasing the bend) as you apply the heat. The usual practice is to keep the heat on until the wrong-way movement is about three times the desired right-way shrinkage.
Wonderful video and great instructions on what to expect and why. Thank you for taking the time to share this.
Nice job keith. Ive often wondered how het straightening was done, now youve given me a pretty good idea. Maybe ill get to try it someday.
Mark
There was something sold for Copper pipe work that you would use as a between the copper pipe and the wood frame it like a 1/2 in thick and 8 x 12 used a shield for the wood (made out of some type of cloth material). Hardware stores have them in the pluming section. It does a good job of keeping heat away when you have to sweat copper in a wall.
Cool video. I Didn't even know that heat straightening was a thing until now. When you were polishing the shaft at the end of the video it was interesting that the lathe took quite a while to get up to full speed. Sounded somewhat like a turbine.
Thanks for sharing Keith... I have an ACME threaded lathe compound screw with a slight "S" bend in it that I think should benefit from this straightening technique. I was just going to machine a new one so got nothing to lose by trying this...
a few years ago union pacific flame straightened a bridge near my house. it is 97 years old now and still carrying up to 20 main trains per day....2 men worked for 2 weeks with rosebuds heating the bottoms of I beams...the bridge amounts to a bunch of beams laid on top of concrete buttress, covered with wood and gravel, it would be interesting to lay that aside for a few weeks then remeasure it to see if it changes with time
Nicely done sir!
I need to straighten a bent drill press spindle, that I can’t buy a replacement part.
I have no Lathe, no oxy - acetylene torch, and no run out dial indicator, so with just a vice & butane torch & straight edge, I’m guessing I’ll have to employ a hardwood 2 x 4 & some leverage & wing it and see how I go!
Still handy to see the principle at work by an expert.
That's some quality work right there. I'd be more than happy to duplicate that result.
midway ww2
Don't let people get under your skin by questioning your decisions. I would just tell them "Thanks for the feedback but It's my shop, my lathe, and my job. You can do it any way you want." For example, in steel construction, we don't heat the steel so hot but we apply considerable force to coax a structural member into the desired position. But those are very different grades of steel from steel shafting with very different loading patterns.
Someone else may already have suggested this, but I reckon a handy addition to a dial indicator is an "elephant's foot", basically a large diameter thin cylinder (like a coin only smaller, with a screwed extension) which fits in place of the usual ball-ended tip, enabling clocking up over a thread, keyway, tips of gear teeth, or whatever, without the tip descending into the valleys. You can make them, or buy them.
In the last few years I've learned a lot about heat straightening, since watching a couple of youTube videos on the underlying mechanism from the superb channel "An Engineer's Findings". every thing I've attempted since then has worked, plus I now have an understanding of weld distortion, something which had eluded and frustrated me previously. I've only watched to 12:10 so far, but I'm going out on a limb to say that reheating that first spot is not likely to produce much further action. I can see why Keith chose to do that, because there's no point trying elsewhere because that's clearly where the bend is concentrated. I perhaps would have tried the face immediately beside (to the left of) the spot he heated. If that helped but more was needed, I'd try a could of shrinks immediately adjacent to the first one and on the same cylindrical surface, one each side, at the same distance from the face referred to above.
So now I'm going to watch what really happened as opposed to what I think will happen.
So yes, reheating the first spot didn't do it. Keith actually tried something I considered and discarded, which was to heat further away from the face. I realised that would reduce the runout at the end of the shaft (which it did) but I felt it would leave the shaft slightly bent, like a question mark which had been almost straightened out but not quite. In other words, the left and right ends of the shaft would be true, but not the middle. (Another way of describing it would be a skipping rope)
I learn so much from these clips my heds gon splod
+bryan lawless Thanks!
Always thought that you drew metal using heat and cold. (the side that you wanted the metal to travel, would be where you put the heat) We would use the dial indicators several places and get the reference points, like you did. We would draw 12 to 18 ft. x 4" agitator shafts back into spec, but we would put the heat on the side, the way we wanted it to draw, then cool it with ice and sometimes co2. The heat caused it to expand, then the cold drew it back past were it was before applying the heat.
Thanks so much for posting this.....We learned some things together it by your sharing this video.
Thanks for the video. Been looking into this method for a little while, and plan on giving it a try this weekend.
I see comments throwing words like "temper" and "quenching" around.
Keith didn't wet it down from anywhere near critical temp, but for some steels the localized heat will make the rest of the spindle act as enough of a heat sink to cause problems.
Whatever steel it is, a little or alot of stress is introduced. For this high speed use a stress relief at 5-600 C could be a good idea, and I'd be interested to see if that interferred with the "set" gained by straightening.
Regardless of how and why it is a neat straitening proses!!!.... IIII LIKE IT.
Thank you, Keith
Awesome video! Learned something new. Thanks
Sometimes, after a treatment like that you can “ring” it sharply with a steel hammer to relieve the stress and the runout will change slightly. Doesn’t hurt to check it again.
Keith, I'm wondering how you could check to make sure the spindle is straight on the arbor? For example, if you had a burr or a highspot on the area which the spindle registers on the arbor.
From 15:45 to 16:10 it sounds like your lathe is picking up speed?? Is that even possible? Thought it was a geared head? Makes me want to get the tach out now.
The only thing I was thinking was if the lathe was wired 480V but was being fed 240V power. Under big loads like running high gear I have seen this same thing where it takes a bit to get to full speed because of the lower voltage. Probably just dopler effect from mic position though like you said.
I heard this also on the last video where he turned and threaded the 3/4" spindle, in the same situation where he geared the speed up for polishing. My guess is that the motor is struggling a little to spin up that massive 4-jaw chuck. In higher gears, the motor provides more speed and less power, so it takes more time to accelerate to the speed specified on the motor.
Yes, a geared head means that the chuck is turning at a fixed ratio relative to the motor speed....but the motor speed can vary depending on load, and a high gear places a larger load on the motor.
The doppler effect will be insignificant at the speeds that Keith is moving around the lathe, so that's certainly not the explanation.
i thought i hear the same thing also lathe picking up speed lol.
i used to straighten 40' and 60' trailers by putting heat in to the neck of the trailer similar sort of thing but on a bigger scale use to put the heat in the shape of a v
*****
i was doing this some 30 years ago when i was a whipper snapper lol
I thought that when you heated the metal red hot and quenched it the spot would shrink, causing the bend to be worse. Instead, heating and quenching froze the metal in the expanded condition, correcting the bend. I see I was wrong in my analysis so I learned a lot from this video.
I felt it was done in reverse as well. I can't explain why it went the correct way unless there was some normalizing going on.
Love your videos keep them coming very interesting
Thanks Keith, you just taught me something!
I have a sewing machine shaft (13/32") I've been trying to straighten - I might try this!
In the exchanges between Bill Lewis and Tom Lipton, I noticed that Tom interpreted Keith's referring to the side with the higher indicator reading as the "high side" or "high spot" of the bend. I prefer concave or convex, and don't see how heating, then cooling, on the concave side got the result that it did - and I've read Tom's book, with particular attention to this chapter.
Heat is 1 amazing way to accomplishing many task at hand. And a fine job at that if i do say so my self.
Very informative and your skill level is obvious. One suggestion - tell us something 1 time! eg.: several times you informed us you were not an expert - got it.
Read some of the comments. Some people did not get it. Maybe he should have said it a few more times.
keith,nice job.I would chuck up the spindle and check the run out on the face of the spindle and maybe reface.
I know it’s been years since this was done but this process was in reverse. The correct way to straighten with a flame on a solid bar is to put the low end down and heat the opposite end top. And do not use coolant. This video shows the opposite working. Baffling. But I think I know why. If you try to straighten a tube or hollow section you use this method as shown in this video. If you look when he removes the shaft to show you the threaded section it looks as though there is a certain amount of counterbore which in effect makes this a solid bar at one end and a hollow bar at the other. Therefore he is actually straightening a hollow section. I worked in a reclaimation engineers shop on a large dock using this process to straighten shafts up to 6” diameter up to 10 feet long. And hollow sections too. It could take all day to straighten a shaft as you had to wait for the shaft to cool. I have seen comments stating this process is the opposite of what most people do. Jeff
Exactly, the metal actually shrinks as it cools, it doesn’t stretch!
cool process bro.. always wondered how they did that.
Seeya
Dude
Hi Keith, Thanks for the flame straighting vidio.. I am going to try it myself and I think like most techniques practice makes perfect.. Harvey
Most likely that part wasn't bent in the shaft. the way its built is essentially two cylinders joined by a plane. The plane (where it sits flat on the end of the spindle) is probably where it deformed. After getting it straight, it probably would have been best to face the mounting surface off on the inside, but that probably would have been overkill. Either way, you did salvage a damaged part.
Very interesting
Thumbs up from Sweden
11:46 Do you have any idea if you can do this with a MAP gas torch? Also do you think you have to get it red hot inorder for it to permanently bend? The reason I ask is I have a bent spindle that I'm thinking of straightening like this but I'm worried about affecting the heat treatment of the splined shaft. Plus I REALLY REALLY REALLY don't want to (or even have the means to) remake the splined spindle with a MT2 on one end.
Seems to me tho that in doing this aren't you tempering out any of the hardening that has been put into this shaft. Is that an issue or are we to assum it had no hardening to begin with. If that's the case do you still get the straw thru purple colors when heating campletely annealed steel? I haven't done enough metalwork to know all the details like this yet as I've only just started into smithing casting and machining.
It might be worth having a word with Keith Fenner about this proccess. He cools the hot spot very rapidly and I suspect this might give a sharper response to the bend you create. Maybe you would be able to reduce this run out even more. By the way was that a proper engineers sponge or just a regular household type?
i guess it got bent near the base from some overload issue it had, or some big tree trunk crashed into the cutter
Locked in going though your old videos (David)
Interesting, I have a 2hp Electric motor w/ bent shaft. I would like to try to salvage vs the purchase of new. I'll let you know how it goes.
14:57 @AvE would appreciate that diss to woodworking. I totally get it though and it's something I struggle with myself going from metalworking to woodworking-that is the completely different dimensional stability between their materials.
...we used to straighten crankshafts in a press between v-blocks...
...a little rap with a lead hammer to give it a set...
Don't the heated area contracts more then before? I saw many videos talk about heating on high spot rather than low spot !
Would the part have to be annealed once the process is completed? Assuming it is tool steel.
I've never done this before but when you cool the metal, would it have more of an effect if you just touch the sponge to the side opposite the heated spot?
Great advice!
The other Keith is heavy into this but will not show it on line.....trade secret. It sets his shafting apart from competition. Nice job Keith.
Great video.
Many thanks, that's been most interesting and informative. Is there any reason why this technique could not be used with shapes of shaft e.g. square, rectangular or even angle iron?
Nice save
Very nice and I really enjoyed this! Thank you!
+Arlyn Smith Thanks for watching!
Wood working equipment often times turns at high RPMs. I would be concerned with vibration, especially with a heavy nut spinning on the end of it.
two points - did you make sure the large diameter in the chuks was centralised - and is that tool steel !!!!!
I'm guessing that's Mrs. Rucker's dish pan?
puck pan from hospital
Best plan-first try to straighten the spindle- if successful great- if not turn it down to make the 3/4 one, then use your material to make a new 1.25 unit.