Lathe cross slide conversion to a ball screw

[tonyfoale]

I had a lot of backlash in the cross slide feed screw, which made it inconvenient to use and difficult to turn accurately. I have had the notion to change it to a ball screw running around in my mind for quite some time and recently I bit the bullet.

Here is a video link:

The original lead screw was 15 mm in diameter, the ball screws came in 16 and 14 mm. I choose the 16 mm which was a mistake, you can see in the video how much I had to cut off the ball nut to get it to fit. The 14 mm size would have made that easier and still been perfectly adequate. We live and learn.

I am over the moon with the results of the conversion and have no hesitation in recommending it to anyone. There were some tricky setups needed to machine things accurately but they are fully explained in the video. Here are a few stills.

Click thumbnails for full size.

[DIYSwede]

Excellent work Tony - and explanations are very good throughout, IMHO.
For a while I've been on the lookout for LH <12 mm dia ball screws preferably with a ca 3 mm pitch w/o any success...
Q: Isn't the movement so darned smooth now, that the cross slide will move when turning due to the unbalanced improvised handwheel?

Keep up the good work and ATB

Johan

[tonyfoale]

For a while I've been on the lookout for LH <12 mm dia ball screws preferably with a ca 3 mm pitch w/o any success...
Q: Isn't the movement so darned smooth now, that the cross slide will move when turning due to the unbalanced improvised handwheel?
Johan

I have been unable to find a LH version also.
No, there is no problem with unwanted movements. The action is very smooth but not loose, there is enough friction from the dirt seals to prevent back driving and the unbalance from the handle is trivial in comparison.

[DIYer]

Thanks tonyfoale! We've added your Cross Slide Screw Conversion to our Lathe Accessories category,
as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:

Cross Slide Screw Conversion by tonyfoale

tags: lathe, modification

[tonyfoale]

Paul Compton pointed out in the Youtube comments that LH ball screws are rare because these screws are mainly used in CNC machines and it is simply a matter of software as to which way they turn. So there is no need to make both RH and LH screws.

[nova_robotics]

That is a beautiful thing. You could drive a truck through the slop in my cross-slide. Hmmmm..........

[Toolmaker51]

Don't recall ever handling a cross slide equipped with a ball screw. Check that, just one, a Haas TL model. It runs Conversational CNC or manual using the built-in DRO. That handle was counterbalanced but still didn't feel as it would react to pressure and turn on it's own. When you let go, it stopped.

I'm certain elimination of backlash is part of that, with a common leadscrew subject to vibration, wear and imperfect mating surfaces.
It's also why climb milling [on ball screws] is OK, even by hand. We are so used to avoiding it, the sensations of touch, sound and vision can be unnerving.

I'll affirm rarity of LH ball screws, even in balancing mechanisms with 2 screws. Reversible motors and coding alleviate them.
The very best old [ie serious] heavy milling machines had anti-backlash mechanisms using 1 each. A few incorporated manual rapid traverse too, by choosing right or left handwheel. That expedited production, with an unloaded traverse motion not subject to feed rate.

[gatz]

Great work, Tony
McMaster-Carr has a few English LH ball screws/nuts; probably not useful over in Spain

But, I did find this company that has LH metric.. might be worth a look.

https://us.misumi-ec.com/vona2/mech/...0029090%3A%3Ac

[Toolmaker51]

McMaster-Carr? Not Amuzin, Kneebaye, Grunger, MshooshC or other inconsequential upstarts? Don't get me going on Asian marketers, that lose grip on your search terms.......like endmills and lipstick! What, at distance they look alike?
McMaster-Carr originated the concept of branched industrial warehousing, and ready supply lines. The others are, well just that, the others. There is even a thriving market for out of date MC catalogs, you don't get one without being a regular customer. The online version hands down exists as THE most easily navigated reference, especially when thousands upon thousands of categories [not mere items, lol] are described clearly.
I'm just a dedicated fan; not a stockholder!
But they respond w-o-r-l-d-w-i-d-e!

[gatz]

McMaster-Carr was our "go-to" source for many years in the tool & die business.
They were always, ALWAYS good on deliveries, and had most anything you could want.
Perishable tooling was usually bought from other companies that specialized in same.