Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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  #1   Report Post  
Gunner
 
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Default 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. ****.

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..
  #2   Report Post  
wws
 
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Default Straighten a acme lead screw?


"Gunner" wrote in message
...
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. ****.

Anyone know the best way to straighten an acme lead screw?

Gunner

snip

Does it look like a bananna or the letter L?



  #4   Report Post  
Dan Caster
 
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Default Straighten a acme lead screw?

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
Anyone know the best way to straighten an acme lead screw?

Gunner

  #5   Report Post  
Ian Stirling
 
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Default Straighten a acme lead screw?

In rec.crafts.metalworking Gunner wrote:
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. ****.

Anyone know the best way to straighten an acme lead screw?


Is it bent, or BENT?
Are we talking a couple of degrees, or could you enter it in an interesting
knots contest.

--
http://inquisitor.i.am/ | | Ian Stirling.
---------------------------+-------------------------+--------------------------
Tad Williams has an interesting new fantasy: http://www.shadowmarch.com/


  #6   Report Post  
Abrasha
 
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Default Straighten a acme lead screw?

Gunner wrote:

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. ****.

Anyone know the best way to straighten an acme lead screw?


You need access to one of these
http://www.thomasregister.com/olc/57410102/straight.htm

or maybe you could make one of these to bend it straight again

http://www.americanartifacts.com/smma/barnes/b17.htm

Good luck

Abrasha
http://www.abrasha.com
  #7   Report Post  
clay
 
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Default Straighten a acme lead screw?

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:

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. ****.

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..


  #8   Report Post  
PrecisionMachinisT
 
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Default Straighten a acme lead screw?


"Gunner" wrote in message
...
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. ****.

Anyone know the best way to straighten an acme lead screw?


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......

--

SVL


  #9   Report Post  
Gunner
 
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Default Straighten a acme lead screw?

On Mon, 22 Sep 2003 06:24:20 -0500, "wws" wrote:


"Gunner" wrote in message
.. .
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. ****.

Anyone know the best way to straighten an acme lead screw?

Gunner

snip

Does it look like a bananna or the letter L?


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..
  #11   Report Post  
Gunner
 
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Default Straighten a acme lead screw?

On Mon, 22 Sep 2003 16:23:48 +0000 (UTC), Ian Stirling
wrote:

In rec.crafts.metalworking Gunner wrote:
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. ****.

Anyone know the best way to straighten an acme lead screw?


Is it bent, or BENT?
Are we talking a couple of degrees, or could you enter it in an interesting
knots contest.

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..
  #12   Report Post  
Gunner
 
Posts: n/a
Default Straighten a acme lead screw?

On Mon, 22 Sep 2003 16:28:49 GMT, Abrasha wrote:

Gunner wrote:

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. ****.

Anyone know the best way to straighten an acme lead screw?


You need access to one of these
http://www.thomasregister.com/olc/57410102/straight.htm

or maybe you could make one of these to bend it straight again

http://www.americanartifacts.com/smma/barnes/b17.htm

Good luck

Abrasha
http://www.abrasha.com


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..
  #13   Report Post  
Gunner
 
Posts: n/a
Default Straighten a acme lead screw?

On Mon, 22 Sep 2003 17:27:14 GMT, clay
wrote:


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


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..
  #14   Report Post  
Gunner
 
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Default Straighten a acme lead screw?

On Mon, 22 Sep 2003 10:59:07 -0700, "PrecisionMachinisT"
wrote:


"Gunner" wrote in message
.. .
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. ****.

Anyone know the best way to straighten an acme lead screw?


Gunner,

Whats the dia and pitch ?

Ill check

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......


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..
  #15   Report Post  
jim rozen
 
Posts: n/a
Default Straighten a acme lead screw?

In article , Gunner says...

On Mon, 22 Sep 2003 17:27:14 GMT, clay
wrote:


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.


This is the way I thought to do it. Thanks for the info.


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

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================



  #16   Report Post  
Jack Erbes
 
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Default Straighten a acme lead screw?

On 22 Sep 2003 09:23:12 -0700, (Dan Caster) wrote:

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.


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.



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  #17   Report Post  
Tom Wait
 
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Default Straighten a acme lead screw?

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
"Gunner" wrote in message
...
On Mon, 22 Sep 2003 17:27:14 GMT, clay
wrote:


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


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..



  #18   Report Post  
Peter Reilley
 
Posts: n/a
Default Straighten a acme lead screw?

In rec.crafts.metalworking Gunner wrote:
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. ****.

Anyone know the best way to straighten an acme lead screw?


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.


  #19   Report Post  
Kirk Gordon
 
Posts: n/a
Default Straighten a acme lead screw?

Gunner wrote:
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. ****.

Anyone know the best way to straighten an acme lead screw?


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
--
I'm sick of spam.
The 2 in my address doesn't belong there.

  #20   Report Post  
Gary Brady
 
Posts: n/a
Default Straighten a acme lead screw?

Anyone know the best way to straighten an acme lead screw?

Sounds like a job for a lead hammer with a soft 2x4 underneath for padding.
Gary Brady
Austin, TX


  #21   Report Post  
Eric R Snow
 
Posts: n/a
Default Straighten a acme lead screw?

On Mon, 22 Sep 2003 10:20:50 GMT, Gunner
wrote:

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. ****.

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..

Greetings Gunner,
I have straightened lots of shafts. And got 'em really straight. This
is what worked for me. Saw vee blocks out of aluminum. The shaft rests
on these in a hydraulic press. Beneath the shaft mount a 1 inch travel
indicator. Rotate the shaft to find the high spot and use an aluminum
pusher between the ram and the shaft. When doing threaded shafts I
used a wide indicator point that bridged the crests of the threads so
that the indicator didn't need to be moved constantly to find the high
spot. Start to apply pressure and note where the indicator is. Relieve
pressure and see how much bend was taken out. By applying more and
more pressure and noting how much indicator travel equals how much
bend removed you can guess how much firther you will need to go. Since
the aluminum crushes with pressure you need to rotate the shaft each
time when it gets close to straight to guage how straight it is. When
the shaft starts to yield a little it will take less movement to get
the same amount of straightening than when first starting out. When
the shaft gets close to straight it will be very easy to over bend. If
this happens it will take much less pressure the opposite way to put
the bend back in. To get the shaft really straight you will need to
move it in .001 increments. With a manual hydraulic press I have used
a long bar on the pump so it is easy to depress and so a large
movement of the handle translates into minute movements of the ram.
You know my number so feel free to call if you want more help.
Cheers,
Eric R Snow,
E T Precision Machine
  #22   Report Post  
clay
 
Posts: n/a
Default Straighten a acme lead screw?

I can't believe you snipped my great story!!!!!

Gunner wrote:

On Mon, 22 Sep 2003 17:27:14 GMT, clay
wrote:


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


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..


  #23   Report Post  
Stanley Dornfeld
 
Posts: n/a
Default Straighten a acme lead screw?

Very Good information.

Regards,

Stan-
"Eric R Snow" wrote in message
...
On Mon, 22 Sep 2003 10:20:50 GMT, Gunner
wrote:

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. ****.

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..

Greetings Gunner,
I have straightened lots of shafts. And got 'em really straight. This
is what worked for me. Saw vee blocks out of aluminum. The shaft rests
on these in a hydraulic press. Beneath the shaft mount a 1 inch travel
indicator. Rotate the shaft to find the high spot and use an aluminum
pusher between the ram and the shaft. When doing threaded shafts I
used a wide indicator point that bridged the crests of the threads so
that the indicator didn't need to be moved constantly to find the high
spot. Start to apply pressure and note where the indicator is. Relieve
pressure and see how much bend was taken out. By applying more and
more pressure and noting how much indicator travel equals how much
bend removed you can guess how much firther you will need to go. Since
the aluminum crushes with pressure you need to rotate the shaft each
time when it gets close to straight to guage how straight it is. When
the shaft starts to yield a little it will take less movement to get
the same amount of straightening than when first starting out. When
the shaft gets close to straight it will be very easy to over bend. If
this happens it will take much less pressure the opposite way to put
the bend back in. To get the shaft really straight you will need to
move it in .001 increments. With a manual hydraulic press I have used
a long bar on the pump so it is easy to depress and so a large
movement of the handle translates into minute movements of the ram.
You know my number so feel free to call if you want more help.
Cheers,
Eric R Snow,
E T Precision Machine



  #24   Report Post  
Ken Davey
 
Posts: n/a
Default Straighten a acme lead screw?


"Gary Brady" wrote in message
...
Anyone know the best way to straighten an acme lead screw?


Sounds like a job for a lead hammer with a soft 2x4 underneath for

padding.
Gary Brady
Austin, TX


The way I see it is there is no way to restore precision without replacing
the screw. If absolute precision (in that axis - in otherwords relative
position is is enough) is not needed then straightening (an lapping in) to
the point of non-binding may suffice.
Your call.

Hope this helps.
Ken.


  #25   Report Post  
Gunner
 
Posts: n/a
Default Straighten a acme lead screw?

On Tue, 23 Sep 2003 01:21:35 GMT, clay
wrote:

I can't believe you snipped my great story!!!!!


Terribly sorry old man..Im still stressing about dropping the Gorton
Pantograph...

Gunner


Gunner wrote:

On Mon, 22 Sep 2003 17:27:14 GMT, clay
wrote:


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


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..



"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..


  #26   Report Post  
Gunner
 
Posts: n/a
Default Straighten a acme lead screw?


I removed the table tonight..and the screw is bent in two places, both
of which should be easy to straighten. Unfortunately......the bends
are on the wrong side of the nut, which is bolted to the top of the
knee, under the table. And the screw will turn, but only to the first
bend. Unfortunately again..it only will screw out in one direction, as
there is a flange machined into one end of the screw, so the
direction it comes out..is the one blocked by the bend.

The nut is held in with a couple of large screws, both directly under
the screw. The screw has to come out to get to the nut fasteners..and
it wont come out because of the bend...sigh. Now I have to figure out
a way to straighten it while its still in the machine, though fully
exposed. The nut is a long cast iron "tube" tapped inside for the
thread

I suppose I could take a die grinder and cut away that flange that
holds the screw from going the other direction..but it aint gonna be
pretty....

This is gonna be a head scratcher..

125 thou per revolution, so its 8 TPI by 7/8", if anyone happens to
have 4' of this kicking around...

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..
  #27   Report Post  
Gunner
 
Posts: n/a
Default Straighten a acme lead screw?

On Mon, 22 Sep 2003 19:38:55 -0700, "Ken Davey"
wrote:


"Gary Brady" wrote in message
...
Anyone know the best way to straighten an acme lead screw?


Sounds like a job for a lead hammer with a soft 2x4 underneath for

padding.
Gary Brady
Austin, TX


The way I see it is there is no way to restore precision without replacing
the screw. If absolute precision (in that axis - in otherwords relative
position is is enough) is not needed then straightening (an lapping in) to
the point of non-binding may suffice.
Your call.

Hope this helps.
Ken.

I really dont need to much absolute precision, as this is from a 3-Z
Gorton Pantograph ( I found the data plate and serial number finally).
I doubt if it will ever be used as a mill, but only for a engraver of
letters and numbers on a plate. I have mills for the more precision
work.

If I could get the screw and nut out...Id consider swatting it with a
lead hammer, as its only bent about 5 degrees or so, with another
smaller tweak out on the end just outside of the (broken) thrust
bearing housing, which prevents a collar and the thrust bearing from
coming off.

I removed the table tonight..and the screw is bent in two places, both
of which should be easy to straighten. Unfortunately......the bends
are on the wrong side of the nut, which is bolted to the top of the
knee, under the table. And the screw will turn, but only to the first
bend. Unfortunately again..it only will screw out in one direction, as
there is a flange machined into one end of the screw, so the
direction it comes out..is the one blocked by the bend.

The nut is held in with a couple of large screws, both directly under
the screw. The screw has to come out to get to the nut fasteners..and
it wont come out because of the bend...sigh. Now I have to figure out
a way to straighten it while its still in the machine, though fully
exposed. The nut is a long cast iron "tube" tapped inside for the
thread

I suppose I could take a die grinder and cut away that flange that
holds the screw from going the other direction..but it aint gonna be
pretty....

This is gonna be a head scratcher..

125 thou per revolution, so its 8 TPI by 7/8", if anyone happens to
have 4' of this kicking around...

The beasty is mint. The scraping marks under the table are proud and
there is NO wear anywhere I can find. Not even polising out of the
scraping marks..which ****es me off even more that I dumped it over.
Not that I had much choice..the hoist busted a bolt..but damn....sigh

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..
  #28   Report Post  
Anthony
 
Posts: n/a
Default Straighten a acme lead screw?

Gunner wrote in
:


I removed the table tonight..and the screw is bent in two places, both
of which should be easy to straighten. Unfortunately......the bends
are on the wrong side of the nut, which is bolted to the top of the
knee, under the table. And the screw will turn, but only to the first
bend. Unfortunately again..it only will screw out in one direction, as
there is a flange machined into one end of the screw, so the
direction it comes out..is the one blocked by the bend.

The nut is held in with a couple of large screws, both directly under
the screw. The screw has to come out to get to the nut fasteners..and
it wont come out because of the bend...sigh. Now I have to figure out
a way to straighten it while its still in the machine, though fully
exposed. The nut is a long cast iron "tube" tapped inside for the
thread

I suppose I could take a die grinder and cut away that flange that
holds the screw from going the other direction..but it aint gonna be
pretty....

This is gonna be a head scratcher..

125 thou per revolution, so its 8 TPI by 7/8", if anyone happens to
have 4' of this kicking around...

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..



Gunner,
Try McMaster Carr, they care ACME screws in standard lengths/sizes, and
are relatively inexpensive.


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email
  #29   Report Post  
dann mann
 
Posts: n/a
Default Straighten a acme lead screw?

I might just have 4 feet of that stuff, Came off a large process camera,
I'll let you know tomorrow




  #30   Report Post  
Larry Jaques
 
Posts: n/a
Default Straighten a acme lead screw?

On Tue, 23 Sep 2003 06:16:21 GMT, Gunner
pixelated:


I removed the table tonight..and the screw is bent in two places, both
of which should be easy to straighten. Unfortunately......the bends
are on the wrong side of the nut, which is bolted to the top of the
knee, under the table. And the screw will turn, but only to the first
bend. Unfortunately again..it only will screw out in one direction, as
there is a flange machined into one end of the screw, so the
direction it comes out..is the one blocked by the bend.

The nut is held in with a couple of large screws, both directly under
the screw. The screw has to come out to get to the nut fasteners..and
it wont come out because of the bend...sigh. Now I have to figure out
a way to straighten it while its still in the machine, though fully
exposed. The nut is a long cast iron "tube" tapped inside for the
thread


If you can get to the outside of the bend, maybe a porta-power
bow-and-arrow sling would do it. Wrap cable (bow string) around
the ends of the screw (bow), secure, and insert the porta-power
ram (arrow) in between, against the bend. Pump it straight. Use
additional cables to maintain the integrity of the screw in the
mid points if necessary.


----------------------------------------------------------
--== EAT RIGHT...KEEP FIT...DIE ANYWAY ==--
http://www.diversify.com/stees.html - Schnazzy Tees online
----------------------------------------------------------


  #31   Report Post  
Eric R Snow
 
Posts: n/a
Default Straighten a acme lead screw?

On 22 Sep 2003 17:30:41 -0700, jim rozen
wrote:

In article , Eric R Snow says...

move it in .001 increments. With a manual hydraulic press I have used
a long bar on the pump so it is easy to depress and so a large
movement of the handle translates into minute movements of the ram.


Once again, a pressure gage on the press makes this
easier to do.

Jim

================================================= =
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
================================================= =

Yes Jim, but the indicator shows the movement, which is the most
important thing.
ERS
  #32   Report Post  
Glen
 
Posts: n/a
Default Straighten a acme lead screw?

On Tue, 23 Sep 2003 09:49:22 GMT, Anthony
wrote:

Gunner wrote in
:


I removed the table tonight..and the screw is bent in two places, both
of which should be easy to straighten. Unfortunately......the bends
are on the wrong side of the nut, which is bolted to the top of the
knee, under the table. And the screw will turn, but only to the first
bend. Unfortunately again..it only will screw out in one direction, as
there is a flange machined into one end of the screw, so the
direction it comes out..is the one blocked by the bend.

The nut is held in with a couple of large screws, both directly under
the screw. The screw has to come out to get to the nut fasteners..and
it wont come out because of the bend...sigh. Now I have to figure out
a way to straighten it while its still in the machine, though fully
exposed. The nut is a long cast iron "tube" tapped inside for the
thread

I suppose I could take a die grinder and cut away that flange that
holds the screw from going the other direction..but it aint gonna be
pretty....

This is gonna be a head scratcher..

125 thou per revolution, so its 8 TPI by 7/8", if anyone happens to
have 4' of this kicking around...

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..



Gunner,
Try McMaster Carr, they care ACME screws in standard lengths/sizes, and
are relatively inexpensive.


--
Anthony


MSC has them too, but they are rolled threads. I would think a fellow
could cut an acme thread more accurately in any good lathe. I've made
many of them of 12L14 at the Lumber mill I used to work in. Of course
if the lead screw is worn out you get a sloppy lead thread in your
screw. Cutting acme threads with a follow rest is a bit like juggling
sometimes until one gets used to it.
  #33   Report Post  
\The Unusual Suspect\
 
Posts: n/a
Default Straighten a acme lead screw?


"Gunner" wrote in message
...

I removed the table tonight..and the screw is bent in two places, both
of which should be easy to straighten. Unfortunately......the bends
are on the wrong side of the nut, which is bolted to the top of the
knee, under the table. And the screw will turn, but only to the first
bend. Unfortunately again..it only will screw out in one direction, as
there is a flange machined into one end of the screw, so the
direction it comes out..is the one blocked by the bend.

The nut is held in with a couple of large screws, both directly under
the screw. The screw has to come out to get to the nut fasteners..and
it wont come out because of the bend...sigh. Now I have to figure out
a way to straighten it while its still in the machine, though fully
exposed. The nut is a long cast iron "tube" tapped inside for the
thread

I suppose I could take a die grinder and cut away that flange that
holds the screw from going the other direction..but it aint gonna be
pretty....

This is gonna be a head scratcher..

125 thou per revolution, so its 8 TPI by 7/8", if anyone happens to
have 4' of this kicking around...


Gunner,

The force that bent it was from the handle hitting the dirt, am I correct ?

Can you remove the handle and housing and put a long piece of pipe on it up
almost to the nut?

Or if its on the other side of the nut, maybe use a pinch bar and an
aluminum block, after rotating the bow towards the underside of the
table..... Better yet, get a helper and do both.......

Im straightening aluminum extrusions in the vises, loaded on the cnc before
machining, measuring warpage with an indicator in the spindle, Im using a
16in. crescent wrench and a piece of pipe to add leverage.........

The keyword here is "leverage"......

Good Luck.

--

SVL


  #34   Report Post  
geoff merryweather
 
Posts: n/a
Default Straighten a acme lead screw?

Gunner, have you looked at the precision leadscrews from
http://www.mcmaster.com? My FiL used one to fix up his lathe -
accurate and cheap.
Geoff
  #35   Report Post  
Joel Corwith
 
Posts: n/a
Default Straighten a acme lead screw?



Gunner,

The force that bent it was from the handle hitting the dirt, am I correct

?

So turn the screw 180 and drop it again?



Joel. phx


Can you remove the handle and housing and put a long piece of pipe on it

up
almost to the nut?

Or if its on the other side of the nut, maybe use a pinch bar and an
aluminum block, after rotating the bow towards the underside of the
table..... Better yet, get a helper and do both.......

Im straightening aluminum extrusions in the vises, loaded on the cnc

before
machining, measuring warpage with an indicator in the spindle, Im using a
16in. crescent wrench and a piece of pipe to add leverage.........

The keyword here is "leverage"......

Good Luck.

--

SVL






  #36   Report Post  
Gunner
 
Posts: n/a
Default Straighten a acme lead screw?

On Tue, 23 Sep 2003 17:36:39 +0200, J. Nielsen
wrote:

On Tue, 23 Sep 2003 06:16:21 GMT, Gunner wrote:

The nut is held in with a couple of large screws, both directly under
the screw. The screw has to come out to get to the nut fasteners..and
it wont come out because of the bend...sigh. Now I have to figure out
a way to straighten it while its still in the machine, though fully
exposed. The nut is a long cast iron "tube" tapped inside for the
thread

I suppose I could take a die grinder and cut away that flange that
holds the screw from going the other direction..but it aint gonna be
pretty....


You could try straighten the screw by heating the bend with an acetylene
torch. If you heat it to cherry-red it will bend easily. Perhaps you can
straighten it by running it through the lead nut while it's still red?

Don't worry about ruining the hardening, the screw is probably soft anyway
- besides, it's not a swiss clockwork we're dealing with here. g


I think this is my only option at the moment. The Nut is a hotdog
shaped piece of cast iron, and will not take a lot of pressure, if I
try to do a pipe and force straighting, and there is not too many
places I can clamp it, to take the pressure off the nut. The screw is
pretty darned soft btw.

Master Carr doesnt carry 8 tpi 7/8" acme screw..or its not listed in
my yellow book..sigh..so Ill try the red heat thing with a rosebud,
then back it through the nut, unless anyone
thinks this is a "Bad Idea".

Anyone?

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..
  #37   Report Post  
Gunner
 
Posts: n/a
Default Straighten a acme lead screw?

On 24 Sep 2003 04:26:06 -0500, geoff merryweather
wrote:

Gunner, have you looked at the precision leadscrews from
http://www.mcmaster.com? My FiL used one to fix up his lathe -
accurate and cheap.
Geoff


Yup. No 7/8 x 8 tpi listed. Darn it.

Respects

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..
  #38   Report Post  
Larry Jaques
 
Posts: n/a
Default Straighten a acme lead screw?

On Sat, 27 Sep 2003 09:19:42 GMT, Gunner
pixelated:

Yup. No 7/8 x 8 tpi listed. Darn it.


Y'all can find a steel bar and a file, cain't ya?
It'll be good practice. gd&r


--
Music washes away from the soul the dust of everyday life.
---- --Unknown
  #39   Report Post  
ian R. Weeks
 
Posts: n/a
Default Straighten a acme lead screw?

Dear All, I missed the first part of this posting ,so I dont know the
size of the Lead screw. However 2 years ago I straightened a 3ft 3/4"
screw on a Theil Miller. It was bent 100Thou eccentric but took less
than 1/2 an hour to get within 0.5 thou of concentricity. The method was
suggested by my friend Harold who called It a "Jim Crow".
Take 2 pieces of angle iron I used 2"x2"x6"
long ,on the first I welded a piece of 1/2" square bar on the 2nd at
each end I welded a similar piece. Place the angle iron between the vice
jaws. Mount leadscrew between centres on lathe. "clock maximum
eccentricty, mark ,transfer to vice ,nip gradually,transfer to between
centres,re-clock, transfer to vice-repeat ad nauseam and in about 1/2
hour good as new leadscrew!
Kind Regards IanIn article afn2nvg7s4m0ldkni48gk7mobqee2ur
, geoff merryweather
writes
Gunner, have you looked at the precision leadscrews from
http://www.mcmaster.com? My FiL used one to fix up his lathe -
accurate and cheap.
Geoff


--
ian R. Weeks
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