Cushman Top Jaw Issues

[coreyg089]

Hello first post here, I have an old cushman 10in that came with the new to me lathe I purchased a year ago. I need new top jaws for the chuck because the jaws have been cut (someone tried to fix them) and the runout is terrible around .020, if I take the top jaws off and measure runout on the main jaws(the scroll jaws) its .004.

I asked the cushman guy if you can use the main scroll jaws to hold parts and he wasn't happy with my question haha so I guess that's a no. I've found jaws that I think will work but my top jaws have a male groove and every new replacement jaw I can find on the internet has a female groove. So with that being said the only thing I can think of is to buy key stock from mcmaster and use it to locate the new female groove top jaws and female groove old scroll jaws.
I called cushman and the engineer I spoke with was not helpful and very rude. I've done a ton of research to try and find replacement ones for this old chuck. The chuck model number is 10 B5498, the cushman guy said its old and they don't have parts for old dinosaur chucks.

Here are the specs for the top jaws in there now tongue is .500, centerline to centerline bolt hole is 1.75 with 3/8 bolts. the groove is .312. the width of the jaws is 1.125 length is 3.01 and lastly the tongue location is 1.31 from the jaw front where it grabs the part.

Here are the only jaws I can find to work 8" x 1.259"HT American Standard Tongue & Groove Soft Steel Chuck Jaw Set
But as you can see they have a female groove, I've added photos to help explain my problem. Thanks for the help.

 

[Limy Sami]

W4elcome aboard.

Have a look here money

 

[eKretz]

I assume he would be looking for hard jaws... Soft jaws are going to wear pretty quick in general usage. Unless you want to periodically recut them?

Anyway, all that aside, I'd just regrind the original jaws and call it a day.

 

[Limy Sami]

Looks????? like they do hard as well (but ya won't like the $$ ) money

 

[4GSR]

That's definitely a dinosaur you have there. Time to buy a new chuck....

 

[coreyg089]

Thanks for the info, it would have been nice if the cushman guy would have just told me what the jaws types are called (acme serrated key)haha.

 

[coreyg089]

I would like to regrind them however the replaceable jaws have been cut or reground and now when the chuck fully closes the master jaws touch before the replaceable ones. I guess it wouldn't matter unless I needed to use the thru hole in the chuck.

Yikes thats insanely pricey for hardened ones, i could always heat treat the steel soft jaws maybe.
I would buy a new one but thats easier said then done ha, the backing plate is a L1 tapered key and also big money, I guess ill just have to save up for one.

 

[NC Rick]

I'm not too smart so you should choose another plan. I think I have the same chuck. I hard turned the jaws with some success and then decided I needed soft jaws so I made some. (Never had them before). The time these took me is silly considering the cost of "American standard" Asian ones cost. Meanwhile I bought a cheap 8" Asian job from one of the "usual scumbags" for my rotary table and got a back plate for it also. The best thing I read on this thread "get a new Chuck".

 

[Limy Sami]

I would buy a new one but thats easier said then done ha, the backing plate is a L1 tapered key and also big money, I guess ill just have to save up for one.

No you don't, you use the same backing plate ...or if it's part of the actual chuck you machine away the old chuck until you're left with a backing plate.

 

[Turbowerks]

I have hard turned them with cmng cbn cutters. Works good. Had one chuck i cut the master jaws so i could still get stuff through the chuck. Make sure to load them in the right direction before cutting.


Sent from my iPhone using Tapatalk

 

[Mud]

They are not acme serrated, that's a different animal, generally seen on CNCs of the 80s.
I've never seen exactly what you have, it's clever but unique. I'd suggest calling Small Tools Inc, they specialize in rebuilding chucks, have a lot of inventory, might have what you need.
First. I'd measure the repeatability of your chuck, see if it holds a part in exactly the same place every time it is tightened. If it does, you can regrind your jaws and have a good chuck. If it doesn't, it's probably because the ID of the scroll is worn where it fits the body, and that's probably cause for a new or better used chuck, because a 10" chuck will cost more to rebuild than you can buy another for..
And yes you can turn material in the master jaws without the top jaws, but it's not a good long term strategy.

 

[eKretz]

You can regrind the master jaws to get them out of the way too.

 

[4GSR]

...................................................
I would buy a new one but thats easier said then done ha, the backing plate is a L1 tapered key and also big money, I guess ill just have to save up for one.

I have a 12" Bison Set True 3-jaw chuck sitting here that probably has never been put on a lathe just from the looks of it. It has a L-1 back plate, too. It weighs 137 lbs., would have to go either UPS or Fedex freight. If interested send me a PM and we can talk. Ken

 

[Nmbmxer]

Looks to me like a standard top jaw would fit in one of two locations to increase the holding capacity of the chuck.

 

[Seaman]

I didn't run through all your dimensions, but the male key in the old set is held in with a socket cap screw. If you removed this key, are the old jaws equivalent to an American Standard jaw? If so, get a standard set and use the key to hold them in position. You could then go hog wild and braze, glue, or screw the key to the new jaws as desired.