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Lathe Cross Slide Problem

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Lathe Cross Slide Problem
EdK Offline
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#1
04-18-2014, 02:33 PM
I discovered some time ago that my cross slide has way too much movement in it. I wondered why I could never seem to turn to a correct dimension consistently. It really reared its ugly head after I installed the DRO. It has about 15-20 thousands of movement. I tried the usual like tightening up the gib but that didn't do anything but make it hard to turn the cross slide dial. I played with the set screw on the cross slide nut to tighten up the play but that didn't help much either and it caused the cross slide to bind at some points on the lead screw. So I disassembled the cross slide and took some pictures in hopes of getting some tips on what I can do to decrease the amount of movement in the cross slide.
Some observations.
  • The nut looks like it was made on a Monday using a grinder and a coarse file.
  • The surface where the nut mounts on the underside of the cross slide is a raw cast iron surface.
  • The bushing with the slot in it that the nut is supposed to sit in is a press fit and can't be easily swiveled to line up the nut with the lead screw.

One thing for sure is I need to mill the underside of the cross slide where the nut sits to make a flat surface for it to sit on. Then I need to mill the nut surfaces flat so it will sit on that newly milled flat surface on the cross slide. I'll likely need to shim the nut to line it up with the lead screw. I think I need to take a very small amount off the diameter of the bushing so it can swivel enough to line up the nut with the lead screw.

I'm open to all hints and suggestions on how to fix this problem.

Ed

       

       
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unioncreek Offline
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#2
04-18-2014, 02:58 PM
Ed,

Don't know if this will help. But on my 8x12 HF lathe the compound had a lot of play. Never could get it adjusted out with the split nut. I finally made a brass washer that fit in the recess of the bearing for the compound screw. That took the vast majority out. Hopefully someone will come up with a solution to the problem.

Bob
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EdK Offline
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#3
04-18-2014, 03:46 PM
(04-18-2014, 02:58 PM)unioncreek Wrote: Ed,

Don't know if this will help. But on my 8x12 HF lathe the compound had a lot of play. Never could get it adjusted out with the split nut. I finally made a brass washer that fit in the recess of the bearing for the compound screw. That took the vast majority out. Hopefully someone will come up with a solution to the problem.

Bob

Bob,

My lathe has an adjustment for that. I really think it's a nut mounting problem or a bad lead screw but I'm open to all suggests so thanks for the idea.

Ed
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awemawson Offline
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#4
04-19-2014, 03:03 AM
Definitely a 'COI' issue. Yikes

Change the COI to something from the Western Hemisphere and your problem will be solved.






1742817428 Don't know what COI is 17428174281742817428







Smiley-dancenana try Country of Origin Smiley-dancenana
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Sunset Machine Offline
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#5
04-19-2014, 08:32 AM (This post was last modified: 04-19-2014, 08:42 AM by Sunset Machine.)
Are we talking about backlash, or is the thing wandering around in its slideway? If the latter, remove the nut and blue things up a bit to see where it's bearing.

My Southbend's compound was curved like a bannana, convex side up. As it moved it became loose. Prussian Blue showed it was contacting at opposite ends. A scraper made from an old file fixed it nicely.
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EdK Offline
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#6
04-19-2014, 05:05 PM
I was planning on knocking this bushing out but I noticed it's knurled. I don't know how they could have pressed a knurled bushing into the hole and expect the milled slot to stay at a right angle to the cross slide. It looks to me like the slot is not at a right angle to the cross slide and that might be causing some of my problems. Chin

I need to get the bushing out so I can mill that raw cast iron surface flat for the nut to rest on.

Ed

       
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krv3000 Offline
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#7
04-19-2014, 05:17 PM
hi have you had a go at adjusting the grub screw at the front of the led screw nut its their to remove play in the thread on the led screw and i wood mack a new bush up as the knurling is a bodge sum times used on bushes that the OD is to Small for the hole it gos in so by knurling it you mack it biger so that it will fit the hole
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EdK Offline
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#8
04-19-2014, 05:27 PM
(04-19-2014, 05:17 PM)krv3000 Wrote: hi have you had a go at adjusting the grub screw at the front of the led screw nut its their to remove play in the thread on the led screw and i wood mack a new bush up as the knurling is a bodge sum times used on bushes that the OD is to Small for the hole it gos in so by knurling it you mack it biger so that it will fit the hole

Yes, I have adjusted the set screw to get rid of backlash. I was thinking the same thing about the bushing. Knock it out, enlarge the hole to get rid of the skid marks left by the knurled bushing and make a new, proper bushing.

Ed
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krv3000 Offline
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#9
04-19-2014, 05:53 PM
yep that wood be the way to go
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PixMan Offline
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#10
04-21-2014, 06:58 AM
Is that bushing pressed into a counterbore with a specific depth?

If so it seems to me that the best thing to dow would be to get the bushing out, mill the opening square and parallel, them make a new bronze split nut to fit the screw at the correct centerline height which has a mating square on it.

What size thread is on the screw? Looks like 1/2"-10 Acme?
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