Worn nuts for mill leadscrew

[Gennady]

Hello folks.

My King USA mill started to act erratically for some time. I decided to have a look and yesterday removed table and started diagnosing. To my utter disappointment I discovered that nuts (there are two to take up a slack) are worn completely. I am not sure how this is happened - mill was always generously lubricated, anyway - here is a picture

I will have to rebuild it, so several questions -
1. Is that leadcrew 5 TPI or 6 TPI ? Seems to be right handed? I am a bit confused...

2. OD if this leadscrew is 1.129" - is there closest standard leadscrew. Nearest fractional size is 1 1/4 - does it look right to you, folks ?
3. Regarding fix - would be OK to bore internal diameter, have some decent wall thickness and then to make a threaded insert? OD of the threaded part is 1 3/4". Make a sliding fit, then to solder insert in pace ?

 

[David]

Looks like 5 tpi to me. What markings are on the handwheels for measurements?

 

[PeterT]

This link might help you with common (commercially available) ACME sizes. Maybe its 1.125x5 assuming its an inch graduated machine? Some folks cut their own leadscrews & nuts, some throw some $ at the problem & buy them, all depends on your tooling & abilities & aspirations. Try to find a machine parts/manual, online or otherwise. It will probably state the size there too for confirmation

Acme Lead Screws - Roton Products Inc.

Roton Products is a manufacturer of lead screws, ball screws, & more. View our acme screw engineering data & shop online for your power transmission needs.

www.roton.com

A more accurate way of measuring unknown threads is encompass as many threads as you can. Then just count the threads encompassed & divide by whatever the measurement reading is. In this machine you probably have a pretty good idea to narrow it down, but I'm talking generally if you aren't sure its maybe even metric. Now if you have significant wear, obviously this isn't going to be 100% accurate but maybe you can traverse outside of that wear range.

 

[jcdammeyer]

I'd look at the hand wheels first for markings. Next I'd consider just replacing the screws with ball screws setting the stage for CNC.

 

[Gennady]

Thanks for the response, folks.
here is the marking on hand wheel

It is definitely inch machine.

What I am planning to do is to cut test piece out of alum and see how it fits.

 

[combustable herbage]

I think you could do a sleeve when I did the one on my old mill I had to redo it all.
I have both an acme 29 degree pitch gauge and an acme 29 screw gauge if you plan to make a cutter with hss.
If they are of any help let me know I am happy to lend them to you.

 

[Gennady]

If they are of any help let me know I am happy to lend them to you.

Thanks a lot . I just happened to order these for myself today. But thanks again for the offer.

Folks. I am starting to collect bronze scrap to make a cast. If somebody in Ottawa and vicinities has bronze scrap - even smallest pieces - and willing to donate it please, LMK.

 

[Proxule]

If they are of any help let me know I am happy to lend them to you.

 

[Susquatch]

1. Is that leadcrew 5 TPI or 6 TPI ? Seems to be right handed? I am a bit confused...

I agree with David. Looks like 5 to me. Peter's method is very exact.

I think your confusion about whether it is 5 or 6 comes from counting teeth vs counting cycles (tooth and valley).

2. OD if this leadscrew is 1.129" - is there closest standard leadscrew. Nearest fractional size is 1 1/4 - does it look right to you, folks ?

I'd guess that 1-1/8 is close enough given that 5tpi was so exact. It seems strange for something to be 4 thou bigger than that, but when I take into account that its an acme thread, it is possible. Not only that, but its the nature of an acme thread to be less sensitive to pitch diameter and overall diameter.

3. Regarding fix - would be OK to bore internal diameter, have some decent wall thickness and then to make a threaded insert? OD of the threaded part is 1 3/4". Make a sliding fit, then to solder insert in pace ?

Not what I'd do, but I see no problem doing it.

 

[jcdammeyer]

View attachment 66906

 

[Doggggboy]

Shitfaced, we will be.