Need chuck screw for 8" 4 jaw

wa5cab said:
Look, guys, not everyone subscribes to the mantra that if a needed or wanted item is make-able on whatever equipment they have, then they must make it instead of buying it. In the first place, not everyone is capable of making everything that is potentially make-able on whatever equipment they might have. In the second, some just prefer originals to clones. And in the third, some have things that they want to, need to or must do that won't get done if they spend all of their time making the things to do what they have to, need to or want to do.
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There are two things this forum is terrible at: convincing someone to not buy a new tool they dont need, and talking someone into skipping a project because you can buy it easier. I'm surprised you're not used to this by now! :-D

In seriousness, chances of finding the part in good shape is slim, even slimmer in any reasonable timeframe.
 
I just checked Mcmaster-Carr, they've got Acme rod for about $50 - $60 a piece, from the pic's it looks to be about 3/4" or 7/8" left-hand Acme. Now all we need is that pesky 9/32" square drive hole in the end!
 
If the screw works why not just use it as is ? :dunno: I wouldn't let a different screw hold me up from using a machine . Or ….buy another chuck . Those chucks are a dime a dozen for $100 or less . If you go this route , you'll be the one to have 3 extra screws lying around to sell .
 
Thousands if not tens of thousands of that particular 8" 4-jaw chuck were sold by Atlas (I have one), Sears, and many other companies. Finding the screw or a chuck with the screw should be pretty simple. But the two least likely places on the Internet to find either the chuck cheap or just the screw are here in this Atlas Forum or in the rather similar Atlas-Craftsman Group on groups.io. I have an Atlas lathe and one of the chucks. If I had one extra screw, it probably would not be available for sale. Where you need to look, besides the Wanted forum near the bottom of the Forum list would be in the fora for larger machines. Many of those folks started off with a smaller Atlas, Clausing, Logan or SB machine and have gone on to a larger one for whatever reason. Quite often, they don't manage to sell off all of the bits and pieces that went to the smaller machine.

As for using the repaired one that he has, if the other three screws had a 1/4" square socket, I would agree with Dave. But mine doesn't and his probably doesn't, either. Remember what one most often uses a 4-jaw chuck for. And how many times you usually have to insert the wrench and loosen or tighten each jaw in order to get the part properly set for the operation. Having one jaw out of the four require a different wrench would be a PITA that would certainly justify spending more than a few bucks to get rid of.
 
I'm glad this post started a discussion! I am in no particular rush as I have another 8" 4 jaw chuck (much heavier duty) and a 6" 3 jaw as well. I did think about buying a piece of L hand acme screw and just dealing with the square hole in the end as an option. I have also thought about cutting the socket off the messed up screw, grinding a bit of a V in the cracked portion, and tig welding it back together then just having to clean up the threads with the lathe. I don't currently have any L hand acme threading tooling nor have I ever tried to cut any. As mentioned above, it's not really worth spending $150 on parts and tooling and then 2 days messing with it when I could just buy another chuck if I really needed one...which I don't. The chuck is good otherwise and I just hate to see it sit for years and eventually get scrapped by someone else. I will post an add in the wanted section though. Thanks for the idea!
 
I've seen independent chuck screws for sale on the internet, but only for Bison chucks. And they are expensive.

Are these always acme thread? Could they be square thread?
 
They could be but on the chuck in question, they are most likely Acme. I have what may be the same chuck except sold by Atlas and it is Acme.

But looking at my chuck, I suddenly realized what had been bothering me about the repaired screw. The portion of the screw that was replaced by the socket should mostly be threaded. The threads ran to the end of the original screw.
 
I believe they are L hand acme threads. I also believe this is an Atlas chuck although it is not marked as such it could have been sold under the Craftsman brand I suppose. As far as the repair, the portion of the thread visible in the picture on top just to the R of the socket is the top, factory thread. All of the ground down area seems to be weld that was ground down for clearance around the socket. The thing that bothers me about the screw is the fact that there is still quite a bit of cracked area down below the socket that was not repaired and in fact is not even lined up very well which strangely is leading to binding when the screw is turned.
 
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