Turning and Holding Thin Wall Material Without Distortion
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- Опубліковано 8 лют 2025
- Part 2 to the Impossible inspection results video, this video offers several suggestions to avoid part distortion from clamping pressure.
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I hit the send button before i was done that’s what happens when you’re 82 years old. I’m tired of typing i enjoy all of your videos thank you.
lol
Awesome! I finally see one of your videos BEFORE I need it.
Nice to see that pressure turning has variation. Before I saw pressure turning in your videos, I felt like I had done something shameful.
Bonus takeaway: I found out that I already have a LARGE V-Block for measuring/Inspection; some assembly required.
Sense of dread creeps in...
What is somebody going to ask me to do "as a favour" where I'll need to make something like an External Jaw Spider.
As usual a good presentation. Every machinist should learn how to minimize distortion from the holding and/or machining. This shows ways to do it. However, one should always determine if the distortion is or will be a problem. Unfortunately I witnessed a major oilfield service company spend thousands on distortion that made absolutely no difference. Some engineers have no sense of reality and will specify unnecessarily tight tolerances. If you are a hobby machinist you have final say, so make sure you don’t overdo the precision.
Enjoy your work.
especially in PVC tubing!
@@glasslinger
The pvc was a prop for filming purposes. In practice, when using, let's say, a super alloy made of an extruded tube costing a coupla hundred bucks per foot to make a one off part, this is one of the best methods to use for optimal accuracy in the finished part.
Stan Ervin material makes a slight difference. Some may even exacerbate the issue (like non magnetic stainless steel, cold worked to 140,000 psi minimum yield). But consideration of two ideas should be taken. First and foremost is “is the part fit for purpose?” And how is compliance playing a role. If one is machining to print, then meeting print requirements is paramount, but if not, then the “compliance” factor should be evaluated. It will seldom be, that a part easily distorted by jaw pressure, will be tasked with holding size, shape, or location. It will be the compliant part. If that is the case, does it matter that in a free state it has the “right” measurements, or is it more important that it can “comply” to the “right” measurements? Case in point, as mentioned in my first comment. A fluid displacer that fit over a MWD Sub was specified to a ridiculously tight roundness callout. The only critical dimension (regarding fit) was that the ID was large enough. When being assembled the “displacer” would comply to the Sub with no problem at all, yet the “reliability engineers” forced spending thousands chasing an unnecessary requirement. Fortunately they were finally overruled. Hobby machinists should make sure they are not chasing an unnecessary goal also.
But as you stated, and I alluded to, if one is making a “one of” (short for one of a kind) part, knowing how to hold the part to minimize the effects of holding and machining are skills every machinist should master.
Hi Joe. Again you have done the heavy lifting which is defining exactly what the problem is. Another approach is as follows - Stretch out some cling film on a flat surface. Apply a thin smear of silicone grease to the inside where the part is to be gripped. Apply some Blu Tack or playdough to the edge of the job. Then press firmly onto the cling film to form a liquid proof barrier. Fill the job with two pack epoxy to the desired depth. Alternatively, to conserve epoxy fit a loose fitting plug and let the epoxy just fill the gap. (The plug is reusable). After curing the job can be gripped firmly with minimal distortion. The plug will just push out when finished. This method will work with odd shapes. Cheers John
John Spathonis Great idea. Could the heat of the curing epoxy add additional distortion?
@@836dmar Hi E If the mass of epoxy is large and a fast cure is selected - possibly. The use of a slug with epoxy around the circumference would not raise the temperature at all.
Very interesting. For some time now I've had a project in the back of my mind modifying 4" PVC fittings for my woodworking dust collector, but I'm very glad this video came first. Thank you! I'm sure you have now saved me from a lot of trouble.
I did a project a while back involving PVC pipe (lots of it) and I wasted a lot of time on it before I came up with the spider solution. I think out of everything I tried the spider worked the best. Great minds think alike, Joe. For the smaller stuff (3/4" and 1") I used a modified plug technique that involved several steps.
That spider solution makes perfect sense! one more tool on my list of things to make now.
You'll find many uses for it.
This series is prefect timing for me. I'm starting a project right now to make some tool holder parts for my Acroloc that the stock i'm using is 3" DOM with .250 wall thickness that I'm going to have to turn some features on the inside of. I threw it into the chuck and stuck a .0001 indicator on it and saw that even the pretty heavy steel would distort 2-5 tenths. Should have some videos up soon.
This is a weekly problem I endure with thin walled hydraulic and pneumatic cylinder tubes, especially when they're bigger diameters. I'll be making a few spiders, and try it out. Thank you Joe!
Good luck. Don't use excessive pressure on that spider and you should have good results.
Great part two Joe, thanks for sharing.
Thanks for watching
Thanks so much for taking your valuable time to share your priceless insight with us. Please keep ’em coming!
Another level of magnitude regarding a discussion of the tolerances of thin and flexible materials. Is it appropriate for you to share the tolerance of the parts you’re making, without giving any proprietary information away?
Metrologists! I had the good fortune to manage a 6 person lab, all sheepskined engineers, (I studied Mechanical Engineering but never finished). We had 18k+ instruments, electrical and mechanical, on the books. I learned a tremendous amount but gave as good as I got when we went for, and achieved, ISO9001 certification. So many wonderful heated discussions around logic, common sense, procedures, and statical analysis. Great time!
I like the v block you set up. That was a great ideal.
Hi Joe,
Thanks for these little gems of knowledge. Stay safe.
You sure chose a good field to be able to benefit from your ability to think your way out of boxes! I love how you always snatch victory from the jaws of defeat!
No inanimate object is going to beat you!
This pinch technique reminds me of turning the magnet off on an overhead grinder prior to making the last pass.
Suburban Tool interviewed another shop's machinist and he agreed that was the way to finish up and he also shared that they used to have a window that lined up with the grinder but now it's plywood......hmmm, wonder why :)
My last boss used to give me a project and say 'This is impossible" , then walk away smiling. Right up until he gave me my next impossible job.
@@joepie221 That's hilarious! He knew the right buttons to push!
I, too, love figuring out the impossible. :)
@@joepie221 speaking of impossible, I'd like to propose a project that many would deem to be impossible.
Make a light weight wheel whose only important parts are a center shaft and a strong rim.
Line the rim with relatively small motors which could be anything from battery powered ones salvaged from toys, to bathroom ceiling fan motors...... doesn't matter, just plain Jane off the shelf motors.
Now, bear in mind that the wheel is an infinite series of levers and we all know that levers mechanically amplify power - a child can lift a car with a simple lever.
Next, using a shade tree mechanic clutch (pulley/ bearing assembly on the end of a lever) we tighten a belt and engage an electrical generator.
Many little motors, with their feeble outputs amplified, do the impossible.
Then we use another hillbilly clutch to bring in a heavy flywheel that'll maintain rotation of the device for a short time.
We quickly switch out the power for the rim motors to power from the onboard generator. Once power is switched over, we remove the heavy flywheel and use it somewhere else or put it on the shelf until next time.
So, if we've done our homework, we're now powering our rim motors and supplying power to a refrigerator and a TV, etc.
The humble lever.
The simple device that mechanically amplifies power.
Energy created in ways like this must be gradually done on a grassroots level so that it doesn't tank society.
So, we're the grassroots.
Let's begin the transition to a new way of meeting our needs.
Have some fun with this :)
Thanks, Joe. Learned a lot from your videos. Another tool for my arsenal.
Great to hear!
Thank you Joe 👍 You have the best tips in whole internet.
I appreciate that! Thank you very much.
Well, Duh! Pity I never thought of that! Sometimes the bleeding obvious is just too obvious. Thanks Joe for setting me straight, again. Well done.
Thanks for watching.
Great info, enjoyed both videos and funny as I found a jaw spider in my tooling cabinet and DID NOT know what it was.....instant scrap (in my mind) to a tool!!!
Hi Chuck. Thanks for watching. It looks like a few more screw holes may be in order on your tool. Rainy day project. Stay well.
I've used a plug to cut pvc pipe, it prevented the part from coming out of the chuck... I like that spider idea. Going to make one tomorrow. Simple.. thanks.
Great explanation of the pressure turning process! Have not used that method much on such thin stuff, impressive tolerances on such a flimsy part. Would have thought it would relax more after machining. Most thin stuff like that I have encountered had to fit something od or id and I simply made the tolerance side first and the other supported. Big problem usually being creep changing the diameter.
Thank you for passing your knowledge on.
As always, great stuff Joe Pi
Joe - We sleeve a lot of large bearing housings. 12 to 14 in. And the disk is a light fit in the thin wall Shelby tubing machine the OD & Id
Interesting. Thanks for making the video. I have a 6” diameter six jaw scroll chuck. Six jaw chucks are supposed to be good for holding thin walled parts. But I would have to do a similar experiment to see what kind of results I would obtain. Stay healthy.
They are better than a 3 jaw, thats for sure. I have a video on chuck selection. You should check it out.
The large included angle between the 1-2-3 blocks used to test the part in the video is more suited to detecting the maximum out-of-round in a five lobed shape rather than a three lobed shape. Constant diameter lobed shapes can have any odd number of lobes. In order to detect the full magnitude of the lobbing, the contacts of the three-point measuring system must be arranged to be in phase with the lobing. The contacts need to be hitting all high points simultaneously (or all low points) as the part is rotated in the test setup. For a three lobed shape, the V-block needs a 60-degree included angle and for five lobes, it needs to be 108 degrees included. The tendency to produce such “lobed” cross sections that have relatively constant “diameter” is a perennial issue in centreless grinding. By its nature, the centreless grinding process, wherein the bar stock rolls between a regulating roller and the grinding wheel tends to produce sections with fairly constant “diameter” but not necessarily with circular cross section. So, a nice shiny piece of ground stock that mikes as exactly the required diameter, might not be quite all that it seems.
The large angle setup and inspection is far more accurate than rolling it under a test indicator set by a gage block.
@@joepie221 Yes and no. For a part with three lobes, any separation of the single lower contact point into two contacts, as when rotating the part on a V-block, will begin to reveal that the part is lobed. However, unless the angle of the V-block is optimised for the particular number of lobes (3, 5, 7, etc), the setup will not detect the maximum variation in radii of the part. The contacts need to be spaced around the circle to suit the number of lobes, so that as the part is rotated, it alternates between having all the contacts hitting the crests of lobes and then all contacts hitting the “valleys” between the lobes. Thus, compared with the roughly 120 degree V-block as used in your demonstration setup, an optimum 60 degree V-block would have registered 50% more movement at the indicator. A 90-degree V-block will miss much of the lobing in a 7 or 9 lobed part because 90 degrees is close to the worst possible angle for detecting these lobe numbers. I grant that 5, 7 or 9 jawed chucks are about as rare as rocking horse manure, but the higher lobe numbers can emerge from other processes such as centreless grinding. The required optimum included angle of the V-block is equal to 180-360/N, where N = number of lobes that you are checking for. I appreciate that the main thrust of the video was about distortion of thin walled parts, not the metrology of lobed parts. Thanks again for all the great videos. pmpaspeakingofprecision.com/2010/09/14/5-things-to-know-about-triangle-effect-pseudo-roundness-and-lobing/
Great tip! Thanks for sharing your wisdom with us novices!
Another solution is to use wax - ive used it to fixture and support sheetmetal when milling.
Joe and his spiders. Lol
Thanks for the video Joe.
Fuzzy, steel, bring them on.
Joe please Make a content about milling a helical gear, and its gear train installation and calcations, learned alot on your videos thanks
I realize that your test indicator did not have enough travel, but when I need to remove the minimum material from a distorted part it is the lows on the O.D. that matter the most. It is often a trick to get all the lows to read the same and the highs to be minimized as well. Plus, having match the existing face as closely as practical as well. This is where a 4-jaw chuck with copper pads becomes indispensable. Then there are the creative ways to clamp to the t-slots in the chuck. But, again, my parts are rather large (for your world) iron castings which I have to work with the existing machined features.
The lows would be the target surface.
These tip videos are really useful Joe. Many thanks 👍🏻
I have used Cerrobend to fill in the ID on odd shaped parts. Works great.
Good idea. Use a smaller diameter plug as filler so you don't need as much to fill the gap.
Thanks for the jaw spider idea! I just turned some thin wall copper pipe and made a plug. Not no more!
my last job involved turning down these 4ft tubes of 304 stainless talk about harmonics and distortion. Ended up using spiders a lot.
Use rubber expanding plumbing plugs on both ends and fill the pipe with sand. Harmonics are gone.
Awesome tip Joe, thanks!
I was wondering what your solution to this problem would be, and I wouldn't have thought of the spider, that's great. And I suppose once you've turned one properly round feature, you could then switch to a plug or collar for further operations without throwing the part out of shape.
Absolutely. Any distortion from that point on can be attributed to material stress.
Years ago I used to turn an old English penny in half then sandwich it to turn the edge and press it into a bored out other penny to make a double headed coin.
Another great video of super tips! Nice pants..Joe
You guys don't miss a trick.
Sheer genius! Thanks!
Spider Joe....... If You throw that spider (Time 2:06) at the wolf spider I'm sure about who will be running... Brilliant tip!
Large, thin parts..... Not my game, yet..
At time 5:09 it looks like things are even worse. The needle seams to have left contact with the ring.
very good video..thanks for your time
Bloody useful info!! Thanks. Mal
Glad you enjoyed it
I would suspect that some heat got into the part when cutting it
Then as it cools, it will push and pull it out of concentricity probably allowing for the slight errors seen,
Meaning one would have to make lighter cuts and a spread of time between cuts to keep heat distortion to a min.
Do you think that would answer the distortion encountered
Jaw pressure caused this.
Great tip.
Thanks,
John
Hello Mr. Joe, I remember clearly the first time I watched your UA-cam video, it was a wonderful experience and I quite remember you made a comment that when you see that guy running a lathe with a ring, watch and necklace on tap the 👎 button and since you have your ring on running the lathe I tapped the👎.....................😎😎
Nice try. I politely ask you to specify at what time in the video you see me running this lathe with a ring on.
@@joepie221 This took me 4 reads before I figured out what he was talking about... Been watching your videos for a long time, got my business partner, employees and my father watching your videos, great stuff always. Trolls are funny and this made me laugh enough to today to respond, keep up the delicate work!
@@mattfuchs7626 I appreciate your support. Thanks for the comment.
I think we need a go fund me to get joe some new pants 😂
i'll bet he paid good bucks for that look
They are actually just very old and beat. But would sell for around $100 or more new.
It would seem like if it was a one off part that you could fill the inside with a liquid that would harden into a solid.
depending on the part if thats the case why not just start with solid stock???
@@richardcranium5839 depends on how much stress you have in your stock material. Sometimes you get an oval
Is that a "Jaw Wolf Spider"? I will make myself one of those PDQ
Perfect, Thanks Joe
Thanks for sharing!
Thanks for watching!
Thanks Joe!
Hi Joe,
The sandwich method clearly was an improvement so thanks for that tip... Is there going to be a part 3 showing how to overcome this issue when boring?
Thank you in advance for your help.
Paul,,
You gave me nightmares about giant shop lurking spiders and you now tell me I need a spider! I used to like you Joe .lol
Cool! Great tips! Thanks 👍😁👍
Very clever
Would never have thought to machine like that. Thanks for sharing right to the end 🙏
Thanks for watching!
That was outstanding! Thank you.
Glad you enjoyed it!
Good tip.
Glad you liked it
Joe does enjoy his spiders.
New word, "strenth".
Well said..agree 100%👍
brilliant solution, I'm just going to make one. But who cares what you wear. Knowledge transfer can also be done in swimming trunks. I also have those pants that I don't say goodbye to, why because I don't care when I'm in my element.
I just got off my motorcycle.
Will there be a part 3 about fixing the ID? I hope?
As time permits. Yes.
Pour plaster like liquid to solid- transforming material into it before machining. Like non- shrinking epoxy but something cheaper
I agree. That would work.
Wish I saw this a month ago. Thanks!
Does the center of the spider have to be conc?
Close will assure the correct 3 point contact area lines up with the 120 degree jaws, but close is good enough.
One of those simple things that you say why didn’t I think of that.
Very instructional, can you now true up the I’d to have a radial thickness within.002?
I would make a collar for the part, or toe clamp it to a faceplate for that. I bet I could.
Hey Joe, wondering if you could show how to grind jaws in an independent 4 jaw chuck? There is plenty of info on 3 jaw chucks but not much for independent chucks. Thanks in advance
Thank you for sharing.ATB
as i thought you might do was the pressure holding idea, since there really is no other method i could think of that wouldnt have a lot of problems.
Pressure turning is the way to go.
Thanks for the Lesson Joe. BTW what happened to your hands...bike battle?
New bike gloves and some unfortunate lighting. Looked nasty, but really wasn't as bad as it looked.
@@joepie221 I had one of those back in the 70's. Broke my wrist, didn't hurt too bad but it was nearly impossible to work the turret on the lathe with the cast...removed it and carried on. It speaks to me now and again nearly 50 years later
What about the pressure from the indicator? You got a spring in the part that press on the spring in the indicator: The indicator push back on the part and moves the part instead of the tip in the indicator.
I've done paper thin roulon bushings that the indicator pressure would distort. No joke.
@@joepie221
That's beyond splitting haiirs. That's splitting cilia! What's the durometer of this 'roulon' substance?
@@stanervin6108 - I believe he's referring to 'rulon'. en.wikipedia.org/wiki/Rulon_(plastic)
Could you make a plug a little smaller and 2 side tape it or glue it the peice
A plug is fine if the inner diameter is round.
There is another way to skin a cat.I dont know whats it called but if you make a ring and slit it with a hacksaw and put it in the 3 jaws it will act as a collet.Same thing goes if you need to shorten a screw for example -by using hacksaw and cutting 1 side of a nut it will hold the thread like a collet.just make sure that a slit is in between 2 jaws.
Althou that little spider is a great idea.
How about supergluing to a faceplate and using a second on on a live center?
superglue solves a lot of problems, but is not practical for production.
Hey JP, dig all your stuff. Tnx! Trough watching I learned about & have procured this model General mag base, but haven't yet found the snug you're using. Did you make it or was it a production item? If so, do you know what name or part # to look for? Any help is much appreciated. Tnx again!
Its the body clamp for a Starrett last word indicator with a simple turned pin adapter to fit the B&S clamp. Shown in the attached image. You could easily make one. www.starrett.com/metrology/product-detail/711FSZ
@@joepie221 Thanks for info & tip. I'm sure you're busy & I didn't expect a reply, but it's Super Cool you did. Tnx again!
At 3:40, if you had snugged up the jaw spider, and then tried to rotate it inside the part, the eccentricity would have shown up easily.
very cool /// thanks.
Awesome!
First.
@@joepie221
🏁💰🏆
Another problem with a plug is that being squeezed between the jaw and the plug will cause the part to deform: thinning at the pressure point and expanding sway from it.
If you use bored jaws and lighter pressure, it is unlikely to happen due to the surface area contact.
Eureka. . A jaw spider just what need. . . Thanks.
Joe - We sleeve
Yes you are entirely correct, however, if you back fill with a structural foam you will succeed.
Nesghe Polska, Nesghe Nowa
I wonder how the material turned simultaneously inside and outside would behave
k cool what did I miss why do you want a part that's round on the outside and has varying wall thickness?
The wall thickness is even all the way around, and not even close to being round. Maybe you didn't see part 1.
@@joepie221 now I'm really confused. Quite clearly in this video you are trying to make the outer diameter as round as you can. Quite clearly the wall thickness varies.
@@SoWe1 My comment was referring to the shape of the part I started with. The final part is as you have stated. It will all make sense if you watch part 1. This was a repair/recovery technique video for a very specific condition.
@@joepie221 thx :)
What is your magnetic base?
US General model 387
Great video Joe. I'll try this because I usually use expandable plugs which take some time to make. If I can mention something OT about a subject we talked about earlier: lignum vite. I found out that Russian submarines and the USS Nautilus use it for their prop shaft bearings. Where they get big pieces, I don't know. I figure they use them because they're quieter than metal bearings, just a guess. I thought you'd be interested or I wouldn't have brought it up. Cheers and thanks for the videos. www.core77.com/posts/25224/lignum-vitae-wood-so-bad-ass-its-used-to-make-shaft-bearings-for-nuclear-submarines-and-more-25224
My walking stick is from Jamaica. I don't know if thats the only place the wood grows, but don't they call it the "Iron wood". Thanks for the article. I'll check it out.
@@joepie221 It is also called ironwood along with other species. I never knew it as that as a young tree climber in Md (now I'm in WV.) We had another ironwood that is also heavier than water. Don't know the Latin name. I left those names to my boss.
The Rabbit Channel I’m trying to remember why I looked up lignum vite. I know I was reading about it just a couple of weeks ago. Maybe it’s just the submarine videos I recently watched. Oh well...time to watch Das Boot again. You guys have me thinking about subs again. That and the recent Tom Hanks movie....Greyhound.
A collet-type affair? I think I've done that in the past. Have to try it.
Nice job! Can you true up the inside now? Stay safe CHEERS
Yes I can
Joe pie in his hipster pants :)
Something I have done in the past is super glue this kind of part to a face plate in the lathe.
OK, the OD is within +- .003 But now how to turn the ID concentric? Now that's a trick.
Not a machinist, but now that the OD is done I would just bore out some aluminium and lightly press it into that, machine it that way. Or maybe glue it to a faced part depending on the material. Would be interested to know the correct way though.
I'll make a split cup with a nice fit and gentle pressure. Shouldn't be too tough.
Why not just make a 350* clamp with 2 halves screwed together then center and turn it ?
Because its the OD you need to true up.
Are we just going to ignore his pants?
they are fashion pants! :)
Yes. Yes, we are.
My motorcycle pants.
Mate what happened to your jeans?
Age and abuse. They are actually in style and sell new looking like this for big money. I took the high road and beat them up myself actually working.
👍👍😎👍👍
Cyanoacrylate glue to a verified flat surface. Fly cut id and od in single setup, alternating so as to 'creep up' to final desired dimension.
Drop the mic! 🎤
Holy pants batman
I have never priced jeans like this, but I understand they sell for a lot of money. Especially in Japan.
www.levi.com/US/en_US/clothing/men/jeans/c/levi_clothing_men_jeans/facets/feature-distress/distressed/price/%2475-%24100
Make a plug with glass filled bondo, turn the out, make a mold of the exterior, chuck and turn the inside.
What happened to your jeans.
A whole lot of hard work, years of abuse and some occasional battery acid. Other than that, they have held up well and are actually fashionable in some circles. I wear them when I ride my motorcycle on a hot day.
Joe Pieczynski thanks for responding.
I thought « Joe Spider » was your nickname 🙄😜
I'm sure I have many nick names by now.