Heavy 10 - lenthen leadscrew?

I am swapping out the worn bed on my 3.5' heavy 10 with a less worn one + saddle. The only issue is that the new bed is 4', and my 3.5' leadscrew won't work. I can't find a replacement online either. It is for a single tumbler gearbox and all the one's I've found are for a double tumbler, so the end past the shoulder that goes in the gearbox is longer.

Have any of you ever lengthened your leadscrew? I was thinking of chucking up my 3.5' leadscrew in my other lathe and threading the end of the leadscrew, then screwing/loctiting on a 6" extension to reach the end support bracket.

Thoughts? Anyone try this before? I could also just hold out until I find the right leadscrew because the lathe is not yet put back together.

I have lengthened motor shafts befor. I made one shaft end a male cone and the mating shaft female cone, with the compound angle setting undisturbed for a perfect fit. Both shaft sections were tapped and connected with a stud locktited in. Make the add on section oversized and turn down to match the original shaft axis. I'm sure there are other ways.

Personally, I would rather an original, correct length lead screw to replace the one that's too short.
I understand the difficulty in finding an original might prompt you to explore other options. I'd contact SBLatheman here on the forum if you haven't already. If he can't help, there is a video here:
Southbend 9" Gearbox Conversion Part 3 - COMPLETE! - YouTube
on lengthening a lead screw on a 9" South Bend, it might give you some ideas.
CWC(4)

CWC(4) said:

Personally, I would rather an original, correct length lead screw to replace the one that's too short.
I understand the difficulty in finding an original might prompt you to explore other options. I'd contact SBLatheman here on the forum if you haven't already. If he can't help, there is a video here:
Southbend 9" Gearbox Conversion Part 3 - COMPLETE! - YouTube
on lengthening a lead screw on a 9" South Bend, it might give you some ideas.
CWC(4)

Click to expand...

Thank you, I will check out that video later tonight. Ted doesn't have one and neither does ebay.

mach2 said:

I have lengthened motor shafts befor. I made one shaft end a male cone and the mating shaft female cone, with the compound angle setting undisturbed for a perfect fit. Both shaft sections were tapped and connected with a stud locktited in. Make the add on section oversized and turn down to match the original shaft axis. I'm sure there are other ways.

Click to expand...

I think it's a good starting point, maybe I could machine down 3" or so and then take a bar of the same diameter as the leadscrew and bore out to a press fit, then pin it in a few spots.

Just cut the original one off at the gearbox, pull the stub, bore it the collar, insert ANY 3/4"x8 tpi lead screw with the right key way and pin it.

Makes it easy for future maintenance too.

The 9" and 10k leadscews (model A and B)would work,and those are everywhere.

I see pins used a lot so in must work out ok. One problems is the connection working loose over time. The method I discribed does not require pins if done right. Pins wouldn't hurt though.

The lead screw on my 36" c-c lathe was worn pretty good up at the headstock end. I found an almost new screw from a shorter bed model but obviously it wouldn't drop in. I turned a section of 3/4" steel to match the old one for the outboard support, and cut it to the needed length. Flipped it around and dialed in on the four-jaw, bored and reamed the end to be a light interference fit on the end of the new lead screw. Heated the extension up, droped it on and then cross-drilled for a small pin. It runs concentrically and I've never had a problem with it other than not being able to use power feed or thread on the far right side of the machine, which hasn't posed a problem for me. If needed I could always swap the old screw in because it is good on that end. The "new" one is fully functional on a shorter length machine if wanted, the cross pin hole doesn't hurt anything. This was on an Atlas, but same could be done for the 10L and thread the end of the extension as needed for the support. I'd still fit them together the same way.

Cutting and flipping (as well as stubbing new ends on) isn't hard, it's just a matter of getting everything bored and turned concentrically. The steel is much softer than you might be expecting, very easy to machine (and the reason these screws wear so readily).

Here's a quick series of clips from when I cut and flipped the screw on my 16". I now have brand new threads and drive keyway near the headstock where it's most likely to be needed. The cheapest quote I got for having a new screw made from scratch was around $1,500 and that was from a friend of a friend doing me a favor. For the 16" machines, the screw is 1-1/8 x 6TPI. You can buy 5TPI ACME rolled stock or even ground stock, but 6TPI is a rare animal.

Instagram