What acme thread?

[Athomp]

I have a South Bend 13 that I've had for several years an now there is about .050 backlash on the cross slide. I was thinking of making a new nut for it but I don't know what tap to get. Can anyone tell me what kind of acme thread is used on SBs - is it 29 degree or 15 degree or what?
Thanks

 

[kitno455]

29 degrees. But, before you jump into replacing the nut, the problem could be in two other places- the screw could be worn undersize, or the screw might be moving axially because the thrust bearing is shot.

allan

 

[Illinoyance]

Measure the OD of the screw and the pitch. That will define the thread size. Acme is, by definition, 29 deg. included angle.

 

[iwananew10K]

Just an FYI-

South bend lathe crossfeed leadscrew nut for 13",14",14.5" and 16" | eBay

if you need ACME screw tooand don't want to make it yourself there are also several sources to buy just the threaded rod that you may graft onto your existing front half...(handle shaft and gear)

It's really hard to justify a tap you will only probably use once when you can buy the completed nut cheaper.

 

[GenePoole]

Jayhawkman, a member here (and referenced in the above ebay link), can also rebuild your existing crossfeed leadscrew.

 

[Athomp]

Thank-you but his ad says he doesn't ship to Canada and I'd like to give it a try myself.

Just an FYI-

South bend lathe crossfeed leadscrew nut for 13",14",14.5" and 16" | eBay

if you need ACME screw tooand don't want to make it yourself there are also several sources to buy just the threaded rod that you may graft onto your existing front half...(handle shaft and gear)

It's really hard to justify a tap you will only probably use once when you can buy the completed nut cheaper.

 

[Athomp]

Thanks for the replies.

 

[Tex-VA]

Here's a thread I worked on quite a while ago and it might have the information you're looking for? Good luck, Tex
< http://www.practicalmachinist.com/vb/south-bend-lathes/making-new-cross-slide-acme-screw-150571/ >

 

[yanshi]

It IS 29 degree, know more about ACME thread, you can check the machinery's handbook

Machinery’s Handbook |

by search: ACME thread, you can get enough information

 

[hsracer201]

Just an FYI-

South bend lathe crossfeed leadscrew nut for 13",14",14.5" and 16" | eBay

if you need ACME screw tooand don't want to make it yourself there are also several sources to buy just the threaded rod that you may graft onto your existing front half...(handle shaft and gear)

It's really hard to justify a tap you will only probably use once when you can buy the completed nut cheaper.

If I can hitch hike on this thread instead of starting a new one I will. Where can I find 7/16"x10 LH acme? I have called every supplier of Acme thread that I can find on the internet and each place I call refers me to 3 other places. After calling them all, I still cannot find it. Its to replace a worn section of crossfeed screw on a H10.

 

[iwananew10K]

south bend lathe 1L crossfeed leadscrew rebuild kit | eBay

 

[hsracer201]

south bend lathe 1L crossfeed leadscrew rebuild kit | eBay

Is that long enough for one with a T.A.?

I sent that seller on eBay a message on August 6th inquiring but never got a reply. It's almost October 6th. 2 months. Guess he doesn't want my business.

 

[iwananew10K]

These guys can take care of you-

Products – Miller Machine and Fabrication

 

[tommy1010]

My SB 13 has an 1/2 x 8 tpi cross feed screw thus the 125 division dial on the crank. I do not know what you have but I have gone to 10 tpi crossfeed screws and nuts. You need to get or make a new dial with 100 or 200 divisions if you do. If you have a DRO then it doesn't matter what the dial says. If you have 10tpi now you can get or make that stuff easily. Overseas taps for 1/2 x 10 tpi LH acme are cheap. If you are making the nut make with a backlash eliminating slot and screws. Will last a long time.