Thread: Cross Slide Nut

I have an old Brackenbury and Austin lathe which needs a new cross slide nut. It is 1/2 inch 8 TPI acme thread I think. Does anyone know if there is a Hercus or other equivalent nut that I might be able to buy?I do realise that the spindle is likely to be worn also but I figure a new nut will substantially reduce the backlash.Thanks in advance for any replies.

I think my 12 X 36 lathe is that size , but would have to check.


Stuart do you know what yours is?

Dave

Double check the profile as it may be square.

I just checked and it's no good as it's 5/8 diameter, and is square as Pipeclay said.
Have you worked on these type of lathes Pipeclay?

Dave

I have made a 1/2 square nut for a similar machine,but that was to suit the leadscrew,.

My manual came with detailed drawings of the half nuts, which I thought was good for years down the track when their unavailable.
Did that lathe have drawings or did you have to copy the old one?

Dave

Hello raypat,
I made a cross slide nut for my lathe by making the body of the nut from mild steel and then boring a hole for the leadscrew and then cutting a thread the same profile as the thread on the leadscrew in a piece of phosphor bronze bush, and I then used loctite to secure the bronze bush in the M.S. housing. If the thread ever wears out,I only have to make another bronze section.
Perhaps you could do the same with your worn out nut.
Regards, Russell .

Dave,might of misled you with my reply,when I said similar I was reffering to the age/style of lathe.
The nut in question was complete and not a 1/2 nut,it was permenatly attached to the leadscrew.
It was made to suit the leadscrew the original nut was worn,all I could get from it was the external dimensions.

No problem, Did you use a full width tool for the square thread, or do either side with a smaller tool?
If you ever get a job to fix the half nuts on a a Chinese lathe, you are welcome to a scan of the drawing in my manual, as I presume they are all similar.
Mine has an imperial lead screw.

Dave

Thanks Dave,I did the thread with a full form tool,only problem I had was that for some reason when I set the tool up I didnt leave enough tool out of my bar to get full depth.
Not the easiest thing to track a 1/2" square thread to finish to depth.

raypat,

I have the same lathe, also with a fairly well-worn cross slide nut, so will be interested to hear how you get on. Don't forget, if you are looking for a tap, that it is a left hand thread. Ten TPI LH 1/2" Acme taps are fairly readily available, but the 8 TPI ones seem to be harder to find.

There were a couple of threads recently on the HSM forum on making new cross slide nuts from acetyl plastic, using the unworn part of the acme screw to mould the thread, which might save an awkward bit of small bore internal threading with the lathe:

Making Acetal leadscrew nuts the easy way - The Home Shop Machinist & Machinist's Workshop Magazine's BBS

Having Trouble With Acetal Nuts - The Home Shop Machinist & Machinist's Workshop Magazine's BBS


I have also heard of instances where people have bored out the old nut and successfully cast a new Acme thread in it in Babbitt metal, again using the unworn end of the acme screw as a mould after blackening it with soot so the babbitt won't stick to it.

Regards,

Frank.

Thanks to all for the replies. Rusty I am afraid I am a novice turner and the fix you describe is definitely beyond me at this stage.Franco, I have already made one from acetal and while after several attempts I have managed to get a good profile in the acetal I am having a lot of trouble making a housing for it as there is not much room even after turning the acetal down as much as possible there is little room to leave any meat on the housing. I have attempted two housings so far, one in brass and one in mild steel. So I am left with the problem of finding a nut commercially. As no one suggested there was one close in a similar lathe I will have to look for someone to make me one I guess.Thanks anyway to those that tried to help.Wait, maybe I can try and make the whole thing from acetal. Why didn't I think of that before? Hahahaha.

Originally Posted by pipeclay

Thanks Dave,I did the thread with a full form tool,only problem I had was that for some reason when I set the tool up I didnt leave enough tool out of my bar to get full depth.
Not the easiest thing to track a 1/2" square thread to finish to depth.

I could imagine it would have been a bit of a nightmare getting it realigned. Thanks for the extra info, I am thinking of making a new telescopic cross feed screw to go on a taper attachment. Being the hardest part I thought I would do it first.


Dave

raypat,

Any use to you? Scroll down to see some 8 TPI 1/2" LH Acme nuts. At the price it would seem to be a cheap way to go if one of these could be modified.

1/2 - 8 Left Hand Acme Lead Screws & Nuts for Power Transmission - Roton Products, Inc.

Frank.

Thanks Franco those sleeve nuts look interesting.I will chase them up this week and let you know how I get on. I might even get a length of matching screw thread as well its only $10 a foot. Thanks.