Eliminating Cross/Compound Backlash (7x's)

[2_many_hobbies]

I am interested in hearing what methods owners have used to eliminate backlash in the cross and compound slides of their 7x12/14's

I cant find any good pictures of the ways, screw recess and brass nuts to come up with any ideas for antibacklash nuts.

Essentially this issues is whats holding me back and if I can figure out how to get ~0.001" repeatability across the whole travel ill buy ASAP.

Your pics and solutions welcome, Thanks!

[snoopy27]

The only good solution is a new precision ballscrew. The Sherline solution I am told that works well is to split the brass nut at the bottom, and then slightly compress it.

I bought a precision ballscrew and will be mounting it to the cross slide plate on the opposite side of the spindle. Others have done this, and it is the best compromised solution I have seen.

[2_many_hobbies]

I want to try to stay away from ball screws if its going to be a manual machine because with their 95%+ efficiency you would need to lock the gibs constantly or they would drift with the slightest pressure.

My current lathe uses a brass nut split on the bottom, it requires a squeeze every week or two to keep it within 0.001" but its getting annoying.

I was thinking of making a new nut with a compression spring putting pressure on a second nut. It would take about 0.25 of travel out of the cross slide and im not entirely sure how to mount the second nut yet.

Anyone seen a thread or webpage that goes through the creation of your own antibacklash nuts? All ive found is nuts in delrin blocks kept apart with two screws. It works but wont fit under the cross or compound.

[Twmaster]

I slit the nut on my H-F 7x10 and the backlash went away for a while. It's back now...

How hard is Delrin? Could one make a nut out of that?

[2_many_hobbies]

I don't think delrin will be of much use here, The brass split nut does work and eliminates backlash but it requires a squeeze every few weeks and more often over time.

Im waiting on a length of 1/4-20 stainless steel rod and some springs to make up some antibacklash nuts for my Taig. Its a tight fit but im extending the threaded screw by 4in for a project so its viable now.

[blades]

Delrin is more appropriate for use with an ACME screw. The cross-slide screw on our 7x lathes looks more akin to a standard screw thread. My "solution" for getting rid of slop from the compound slide/screw was to do away with it. Granted, this may not be an acceptable solution for everyone, but it was for me. I replaced it with a solid piece of steel, and it's proven to be very stable. You can see pics of it in my "7x10 Project Started" thread. Other than that, my cross slide has very minimal, if any, backlash at all. I was comfortable enough with it's tolerance to use it as-is on a CNC conversion. A ballscrew conversion would be nice, but small size ballscrews are very expensive on Roton's website.

[2_many_hobbies]

Originally Posted by blades The cross-slide screw on our 7x lathes looks more akin to a standard screw thread

How did you deal with backlash on the cross slide? I have never adjusted one like the 7x's have before (solid nut with a pressure screw in the center) and on the machines I tried out they all had a noticeable amount of backlash in the 0.02" range. My Taig when adjusted is <0.001" across 2.5" and at worst it was 0.002" across 2.5" (I have a DRO still as hand wheel math gets annoying)

[blades]

I don't have anywhere near .020 on mine, although it's seen very little use, so I'm sure it's subject to wear. As I said, there is very minimal backlash in mine, to the extent that I didn't do anything to address what's there.
If you're seeing excessive backlash, I'd look at the screw retainer and see if there's excessive slop between the depth of the c'bore on the back of the retainer vs. the actual thickness of the shoulder on the screw. I haven't yet had mine apart, so I don't know what sort of setup they have for anchoring the nut to the slide, but I would suppose there is the possibility of slop or looseness in that also.