Straighten a acme lead screw?

Tonight..I did a bad thing.
I dumped a Gorton pantograph on its side.
The hoisting gear broke, everything pivoted and it rather gently fell
over on its side. Breaking the tables crossfeed bearing casting on one
side. Which is easily fixable..but it bent the cross feed screw.
Damnit.
Damit to hell. Shit.
Anyone know the best way to straighten an acme lead screw?
Gunner
"Anyone who cannot cope with firearms is not fully human. At best he
is a tolerable subhuman who has learned to wear shoes, bathe and not
make messes in the house."
With appologies to RAH..
Reply to
Gunner
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> Tonight..I did a bad thing. > > I dumped a Gorton pantograph on its side. > > The hoisting gear broke, everything pivoted and it rather gently fell > over on its side. Breaking the tables crossfeed bearing casting on one > side. Which is easily fixable..but it bent the cross feed screw. > > Damnit. > Damit to hell. Shit. > > Anyone know the best way to straighten an acme lead screw? > > Gunner > > snip
Reply to
wws
My 2 thoughts.
[1]Its the kind of thing I'd ask YOU
[2] If it is a common pitch use nuts while working it to avoid over bending [breaking] it. Maybe cut them in half and clamp with them something like that.....
Reply to
Your Name
I watched a TV show where they were straightening shot gun barrels by hand. The owner of the German factory said there was no machine that could do as good a job as the man.
Dan
Gunner wrote in message >
Reply to
Dan Caster
Is it bent, or BENT? Are we talking a couple of degrees, or could you enter it in an interesting knots contest.
Reply to
Ian Stirling
You need access to one of these
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or maybe you could make one of these to bend it straight again
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Good luck Abrasha
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Reply to
Abrasha
First a story. then the advice.
After we had lifted my first (and only) VMC over the house with a 90Ton crane, and placed it mostly in position. My brother, I and a friend were jacking it sideways using a crowbar, and those heavy duty tank rollers. We had everything blocked and all squared away (or so we thought) when all of a sudden in slow motion, the whole thing (all 10,000 lbs) of it started verrry slowly tipping towards my brother and I. I of course was on the ground, setting a vibration pad. During all of this, my mind racing faster than 10,000 pounds can accelerate to maximum squish velocity, considering how dead I was going to be, or, if I could get my arms and legs to react, survive the crash, figure out HOW on earth to tip it back up again. My brother, with more clarity of thought, than is usual for him, reached up, and before our very eyes, stopped it with his hand, from continuing its decent (or rather, tip over motion). I suddenly had gained not only more gratitude for my younger brother, and his ability to think, and move FAST. But a newfound regard for BALANCE. Particularly all things large and cast iron.
Advice. I several times have had to straighten a shaft, but mounting in a lathe chuck near the start of the bend, and fixing a dial indicator on the side and close to the chuck nose, and then very carefully (with a piece of close fintting tube/pipe) bent the shaft just past center, reclamping the newly straighted section, and then repeating the process. At every step, I would spin the shaft to find the high side.
clay
Gunner wrote:
Reply to
clay
Gunner,
Whats the dia and pitch ?
I got a nice piece of brand new saginaw 1.00 dia kicking around here somewhere.....
A 6 ft length, it would be either 4 or 5 tpi-----I paid a purty penny for it many years ago, for a project that was later abandoned......
Reply to
PrecisionMachinisT
Ive not removed it yet, but the end that broke out of the casting now runs out about .5-.75.
I suspect its only a single bend.
Gunner
"Anyone who cannot cope with firearms is not fully human. At best he is a tolerable subhuman who has learned to wear shoes, bathe and not make messes in the house." With appologies to RAH..
Reply to
Gunner
This is actually the first time Ive encountered this sort of problem.
There is an idea.
Gunner
"Anyone who cannot cope with firearms is not fully human. At best he is a tolerable subhuman who has learned to wear shoes, bathe and not make messes in the house." With appologies to RAH..
Reply to
Gunner
The end thats tweaked runs out about .5-.75. Im pretty sure its a single kink. Ill pull it today or next weekend and check
Gunner
"Anyone who cannot cope with firearms is not fully human. At best he is a tolerable subhuman who has learned to wear shoes, bathe and not make messes in the house." With appologies to RAH..
Reply to
Gunner
This is about what Id figured Id have to do. Its not bad bad..but bad enough.
Thanks
Gunner
"Anyone who cannot cope with firearms is not fully human. At best he is a tolerable subhuman who has learned to wear shoes, bathe and not make messes in the house." With appologies to RAH..
Reply to
Gunner
This is the way I thought to do it. Thanks for the info.
Gunner
"Anyone who cannot cope with firearms is not fully human. At best he is a tolerable subhuman who has learned to wear shoes, bathe and not make messes in the house." With appologies to RAH..
Reply to
Gunner
Ill check
Im pretty sure its only around 5/8 or .75 max. Ill pull it today. I think your screw is gonna be a bit big, but thanks anyways.
Gunner
"Anyone who cannot cope with firearms is not fully human. At best he is a tolerable subhuman who has learned to wear shoes, bathe and not make messes in the house." With appologies to RAH..
Reply to
Gunner
Another possibility I would consider is using some aluminum V-blocks, and an hydraulic press - with a pressure gage.
Set the shaft up with the high spot right between centers, and using a dial gage, rotate to get the high spot up. Then come down with a third pusher block and dial in the force to get it to move.
I've done small shafts by putting a dial indicator in the toolpost, check for the close spot, and then bump the shaft with the toolpost only, some certain dial-in on the cross slide. Then re-check for TIR on the indicator, repeat until you know how much dial-in brings it past the yield point.
This works best, with bigger lathes. Or smaller shafts.
For big stuff the press with a pressure gage is nice.
Jim
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Reply to
jim rozen
I toured the FN plant in Belgium in 1958. That was my Dad's idea of tourism. :>)
They had a room with about 8-10 guys using barrel straightening vises that were mounted at eye level from heavy ceiling beams. Each vise had a large handwheel and an Acme or square thread screw that brought a anvil down on the barrel as it lay across two blocks. This was done at eye level and the workmen were looking through the barrel at windows across the room. My Dad commented that they could look at the reflection of the window sill inside the barrel and spot the bends, and rotate the barrel to get it at the top. As they slide the barrels in and out across the blocks, they applied light pressure until they found the point that got the barrel straight. Then they overbent it a little, let it relax to straight.
This may have been the high point of my Dad's vacation but I still remember getting to see the Mannikin Pis statue in downtown Brussels. Oh yeah, we also got to see the 1958 World's Fair.
The next year we got to tour the Norma ammunition manufacturing plant in Sweden.
Reply to
Jack Erbes
My mentor at the gunshop where I learned about such things did the same with bent rifling rods. He put the bent rod in the chuck with two or so inches sticking out. He straightened the rod and as he worked out the bend kept pulling the rod farther out, always checking with the indicator at the end of the rod. When he was done there was two inches of rod in the chuck and no appreciable runout 36" down at the end. I've straighted al. arrows the same way. Tom
Reply to
Tom Wait
My understanding of the straightening process is that with a arbor press, V blocks, and a dial indicator you can straighten most any shaft.
You might need some padding or three half nuts that mesh with the threads. First find the sharpest position of the bend by rotating the shaft in the V blocks and sliding it end to end. Most of the shaft will not be bent. This process should allow you to map the bend quite accurately.
Next place each V block at each end of the bent region of the shaft. Mount the shaft in your arbor press. A hydraulic press is best. Press the shaft a small amount. Measure the deflection with the dial indicator. At first the shaft will spring back to it's original shape when the pressure is released. Increase the amount of deflection that you induce and measure the recoil. At some point you will exceed the yield strength of the shaft. Now you are starting to straighten it. Continue the process until it is straight when you roll the shaft under the indicator. After this process you should probably re-map the bend in the shaft as described above.
However, I am told that there is quite an art to the process. It will probably take you longer than a pro but there is little risk of ruining the shaft.
Pete.
Reply to
Peter Reilley
The trouble with bending a screw is that you'll often deform the thread shapes. If the bend is in a threaded area, then just putting the whole thing back on a single centerline might not make it workable. This might be a replacement job.
KG
Reply to
Kirk Gordon
Sounds like a job for a lead hammer with a soft 2x4 underneath for padding. Gary Brady Austin, TX
Reply to
Gary Brady

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