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10:06 AM
January 12, 2012
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Well….I don't know how I found this site. But I am damn glad I did!!!!
Looks like a great place to be for the novice, and I am definitely one of those. I have an Atlas TH-42 lathe, lantern toolpost and shot lead screw. I've been tinkering manually with it, and getting some decent results, but alas the lathe is 45 minutes away from where I live (at dad's house) so I don't get to spend as much time with it as I would like…..having to work cramps my style y'know?
See ya in the trenches!
10:13 PM
April 27, 2011
Online
Welcome to this site!!!
Everyone loves pics of past projects etc!!!
Mtw fdu.
10:56 PM
January 9, 2009
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Hi Johnpaulh, welcome to the site!
It's a bummer that your lead screw is broken, but as you've discovered you can still do just about everything without it – it just takes some practice. Threading is tuff, but back before leadscrews threads were cut (or chased) by hand. However, back then things weren't made to the tolerances they are now …
Anyway, I'm glad you found the site and you've been finding it useful. Let us know if there is anything we can do to help you out.
By the way, is there any chance the lead screw's shear pin is simply sheared? If so you can make a new pin out of brass? It needs to be made out of something soft like brass so that it can re-shear if things bind up. They are easy to make. They are typically tapered, so measure the diameter of each of the holes going through the part that your leadscrew connects to (I'm not sure what the part is called – a coupler?).
If one hole is larger than the other you've got a tapered shear pin. Chuck up a slightly oversized piece of brass rod and take a file to it to make a new shear pin. Make sure you've got the file flipped around and backwards so that the handle is poingint away from you – you'll want to file from the underside of the part. And don't use a file without a handle. The tang can be dangerous! If you don't have a handle a drilled out golfball works great in a pinch and is surprisingly comfortable.
Once you've got the shear pin filed to the right size cut it off (leave a little longer than you'll need) and tap it into place after aligning the hole in the leadscrew to the holes in the coupler. Tap it in place with a hammer and file away the excess.
And viola! You've got a fixed leadscrew (assuming that the shear pin was the problem) 
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5:27 AM
September 26, 2011
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I saw a site on the web where he used bamboo skewers for shear pins. Cheap (gotta love that), and strong enough to work yet still shear off if a jam is encountered.
5:21 AM
January 12, 2012
Offline
Hi all,
Unfortunately the lead screw simply has the symptoms common for a lathe this old…..it is worn out near the headstock where most of the work has been done. The ACME threads are almost a class 2 (sharp!) in that area, and while I haven't examined the half nuts, I think they are still OK as they engage fine further down the ways.
Once I scrounge up some $$$, I plan to buy a piece of ACME screw stock, and have a local machine shop cut the groove in it for the power crossfeed, then I will turn down the bearing ends and fit it to the lathe.
OR, maybe someone knows of a decent used screw I can pick up cheap? If so, PLEASE let me know…..4/3-8 ACME…not sure of the length on the TH-42….but I own a tape measure!
Right now I have been working with my son on a project, he is building an electric upright bass, so we have encountered some parts where the lathe has been indispensable. I made him a mount for the foot peg, and this weekend we decided instead of using tuning machines at the head (wildly expensive!!!) we will use old school tuning pegs.
The problem? Upright basses haven't used tuning pegs in a century. Soooooooo…..I took some stock and made a tapered "D" reamer to cut the tapered holes, and this weekend the old Atlas will be turning some Marblewood (pretty stuff, and hard as hell) to make the pegs.
The reamer turned out OK (my first taper, and since it is 3.75" long, required some manipulation with the compound, which has a 2.25" travel…..but I did it!) it isn't pretty by any means, but after hardening and honing, we tested it and it cuts a nice tapered hole….which is great because that is what it is supposed to do!
I'm glad I found this site, I've been reading and learning a ton, and I am sure I will have questions as I advance in skills.
Chips Ahoy!
John
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