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Replacement of lead screw on Atlas 618 Lathe with 1/4-20 acme

G

Goldxxx

Active Member
Finding acme 1/2-20 threaded rod is non existent to repair/replace an Atlas 618 lead screw. Would 1/4-20 or 3/8-20 acme have enough strength to pull the table across? Would it also allow me to use the same gear ratios for thread cutting because it’s 20TPI only half the size?

I know I would have to make a new half nut in 1/4 or 3/8. I remember my Sherline Lathe had a small lead screw. I’m just throwing this out there. I must have been absent the day we studied lead screws and gear ratios in machine shop.

Or could it be converted to standard 1/2-20 standard 60 degree threads and still cut decent threads with the gear clusters.
 
Last edited:
pdentrem said:
$11.75 per foot. Cannot beat the price!


1/4 - 20 Right Hand Acme Lead Screws & Nuts for Power Transmission - Roton Products, Inc.

Shop 1/4 - 20 Right Hand Acme from Roton Products, Inc. View all of our products and shop online for your power transmission needs.
www.roton.com
Click to expand...

I’ve bought 1/2” left & right ACME from them. They’re good to deal with and quick, I’d put them on my approved vendors list.

They’re also have some nuts of various configurations.

D :cool:
 
McMaster Carr $219.72( US? maybe and GST ) for a three foot section of 1/2-20 acme is out of price range.
 
This place carries a lot of leadscrew goodies, including matching nuts which you can typically machine to suite & save you potentially expensive taps. Unfortunately USA source & getting anything is becoming more problematic each day until our strike mess gets resolved

Personally, I think your lathe was designed with a leadscrew diameter for a reason. I've seen some guys metri-cate or un-metricate (are those legal words? LOL) & even that had knock on effects of how the screw integrated into the other bits; bushings, bearings, clamshell...

Lead Screws and Ball Screws for Power Transmission - Roton Products

Roton is the premium manufacturer of lead screws, ball screws, and acme screws for power transmission applications. Shop online for your lead screw needs.
www.roton.com
 
PeterT said:
This place carries a lot of leadscrew goodies, including matching nuts which you can typically machine to suite & save you potentially expensive taps. Unfortunately USA source & getting anything is becoming more problematic each day until our strike mess gets resolved

Personally, I think your lathe was designed with a leadscrew diameter for a reason. I've seen some guys metri-cate or un-metricate (are those legal words? LOL) & even that had knock on effects of how the screw integrated into the other bits; bushings, bearings, clamshell...

Lead Screws and Ball Screws for Power Transmission - Roton Products

Roton is the premium manufacturer of lead screws, ball screws, and acme screws for power transmission applications. Shop online for your lead screw needs.
www.roton.com
Click to expand...
A glance at their chart told me they dont make 1/2" with 0.05" lead but they do make a 3/8" 20 which have a static load capacity of over twice that of the 1/4 the OP is considering
 
The McMaster option is a good one for expedience but like everything these days its going to cost you. $220USD plus shipping and taxes and and and and and...
And then you still need to machine it to fit. I hate to say it but ebay may be a better option:
ebay Atlas 618 leadscrews
 
Mcmaster has several grades from $2/foot low strength to $6something/foot for 316 stainless "regular" unf 1/2-20, can you just run a 1/2-20 tap through your nut and it would work?
 
If I got some of the 3/8-20 acme and was able to change the split nut to match, would the gear ratios be the same on the threading table as using the original 1/2-20 lead screw? If I’m asking the right question properly.

I would graft the old lead screw with the new section of acme so the bushings and drive should stay the same.
 
Or am I getting to hung up on it needing to be an acme thread profile where regular V thread will hold up?
 
Goldxxx said:
Or am I getting to hung up on it needing to be an acme thread profile where regular V thread will hold up?
Click to expand...

I can show you first hand what happens when you use 60 degree threaded rod. My mill drill came to me that way. It's a BAD idea. It wears WAAAAY TOO FAST and won't hold a load as well without distorting. There are other problems too, but those should stop you cold.
 
Goldxxx said:
Or am I getting to hung up on it needing to be an acme thread profile where regular V thread will hold up?
Click to expand...
any lead screw profile should work, dont fixate on that, worry about diameter and pitch. You could even buy balls screws, so long as the pitch remains 0.05" but they cost even more

that said buy a matching nut for whatever screw you buy.
 
Tecnico said:
FWIW, I was able to have Roton mail my order, saving on the courier and side stepping the brokerage issue.

Worth asking.

D :cool:
Click to expand...
I was referring to Mcmaster, but yes good point. Many US vendors will ship via USPS if you just ask. Cheapest brokerage fees around
 
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