Anti-Backlash Nut

[Uglydog]

I'm working on a Pratt Whitney 12x30C lathe.
Bed was in good condition, cross slide and compound were a mess.
Cross Slide rebuild came together nicely.
Am now working on the compound. I figured I needed to make a new compound feed screw and nut. However, todays preliminary results showed that the new nut moved backlash from .080 to less than .010 and I'm good with that. This weekend I hope to have final fit up and scraping of the compound flat, tails and gib. Will see if the .010 improves....

Anyway, I thought I'd show pics of the anti-backlash compound feed screw nut I made.
The new nut is as large as I could make it inside the cavity of the compound as I needed to add the two set screws and jam screws.
I've not made an anti-backlash nut before. Spoke with my mentor (Danich) and read some stuff.
My only point in this post is that anyone can do good work, have fun and be safe.
If you've got a backlash problem, you might likely be able to repair your problem without significant expenditures/purchases.

Daryl
MN

 

[sdelivery]

Nice. This and a few other variations exist.
Bridgeport is the one most people see.
Good thinking

 

[brino]

Great work Daryl!
Thanks for posting.
Brian

 

[vtcnc]

If you've got a backlash problem, you might likely be able to repair your problem without significant expenditures/purchases.

Well done. Thanks for sharing. I think many members appreciate this sentiment and the photos showing the results.

 

[WobblyHand]

For those of us who are following along, are there set screws in the tapped holes that basically expand the slit, which in turn takes up the backlash? Just want to make sure I understand the concept.

 

[Uglydog]

For those of us who are following along, are there set screws in the tapped holes that basically expand the slit, which in turn takes up the backlash? Just want to make sure I understand the concept.

Wobbly,
That's exactly what happens in this design.
And the jam screws hold the 10-32 set screws in place.

Typically the feed screw is worn in a specific area.
Thus, finding an adjustment which is works for the range of movement takes some tweaking.

Daryl
MN

 

[motormech1]

Thanks for the post. I might need to do this on my "C" too. Won't know 'til I get the compound reassembled and inspect. What is the most slop you would accept?

 

[sdelivery]

You will feel the handle get harder to turn as you eliminate the backlash.
This will be one clue. most of the used lathes are around a 1/8 to 1/4 turn of the hand wheel, this is in the .010
To .050 range.
You can go tighter but
You would like some feel as you are cutting and you don't want it to be hard to crank.
As always this is my opinion and based on my experiences.