Need chuck screw for 8" 4 jaw

A

AKPrybar

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Looking for a replacement chuck screw for an Atlas/Craftsman 8" 4 jaw chuck. Model number 101-21581 As you can see from the pictures, the previous owner broke the screw and welded on a 1/4" drive socket. I'd like to find a replacement rather than try to make one since I have no way to broach the 9/32 square keyway in the end. Let me know if anyone has any leads. I'm sure they are out there...just a matter of finding one. Thanks!

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I'd still suggest making it. It shouldn't be that difficult, even with the broaching :) For the square inside corner, if it were me I'd either make a broach holder for my tailstock, or just use the mill to make the square.

Basically, it needs a rounded corner anyway, so you hog it out as much as you can with a normal sized endmill. Then, you use a really small one (1/8"?) to touch up the corners.
 
I don't have a mill, and I don't have any of the square broach tooling. A rotary broach would be perfect but too expensive for the part it would produce. By the time I purchase materials and tooling I'd be in over what the chuck is worth. I'm sure someone has a box of these things laying around. I just need to find that guy!
 
If you can make the screw portion on your lathe then you can absolutely turn a round hole into a squareish chuck keyhole for sure and you dont need a mill or those fancy cutters, at least not for the quantity of parts you need made!

Of course if you can find that guy that has some laying around that would fit I think would be the way to go.
 
Latinrascalrg1 said:
If you can make the screw portion on your lathe then you can absolutely turn a round hole into a squareish chuck keyhole for sure and you dont need a mill or those fancy cutters, at least not for the quantity of parts you need made!

Of course if you can find that guy that has some laying around that would fit I think would be the way to go.
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Yeah, broaching is really quite easy, I did it by hand at one point with a vise and a piece of HSS. It took a while, but it worked. Additionally, a rotary broach holder can be made pretty easily with scrap materials based on some of the plans I've seen around here. Its on my list of things to do :)
 
I have seen techniques for creating shafting keyways on the lathe with a simple hss cutter and using the carriage manually (lathe not turning).
I suspect you could drill out the center hole and use the keyway technique to clean out the corners.
It might be easier if you used an internal groove cutter to undercut the bottom of the hole a bit.
 
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.
 
If you wanted to make a replacement, you could probably save a lot of work by starting with a piece of Acme leadscrew. Smaller diameters are cheap and the steel is good. Looks to me like that's how the original was done. You can broach with a boring bar in your tool post as mentioned above.

This would likely be a hard part to replace, which may leave you no choice but to make it, pay someone to make it, or move on to another chuck. I appreciate wa5cab's point, but the reality is that old machine parts can be impossible to find. Just saying. Lots of good ideas from the members of this site, all one has to do is post a question.
 
AKPrybar said:
I don't have a mill, and I don't have any of the square broach tooling. A rotary broach would be perfect but too expensive for the part it would produce. By the time I purchase materials and tooling I'd be in over what the chuck is worth. I'm sure someone has a box of these things laying around. I just need to find that guy!
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Depends on how fast you want it, it may take you a while to find that guy. As others have pointed out broaching can be done with limited tooling, especially when it just has to fit a chuck key not something ultra precise. pontiac428 has a good idea for staring with a piece of Acme leadscrew. I'm just trying to envision a scenario where someone would have an extra one of these.
 
If all else fails, there's probably a machine shop in the area that could turn one out.
Or maybe a member of the forum looking for a challenge?
 
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