Help w/ Cushman Chuck

[motorick]

Trying to get my Atlas 618 lathe up and running. The lathe came with a 5" Cushman chuck that I can't figure out how to separate the back plate from the chuck to clean. Might not even be worth the effort as I still need to source an additional back plate to mount to my 8 tpi thread. Any tips appreciated!

 

[kaymccampbell]

Are the three tiny holes at the perimeter threaded? If they are, then I'd run a bolt down all three and see if they separate things.

 

[DocsMachine]

Put screws in those three threaded holes out on the periphery. Screw them in evenly, and they'll 'jack' the back plate away from the body of the chuck.

And I suspect you'll be better off trying to find a chuck already threaded for 1-1/2"-8. That's a D1-3 chuck, and I'd bet the backplate is integral to the chuck. (That is, the scroll bears against it on the inside.) You probably won't find a "loose" threaded backplate that will fit, and making one would be tricky.

On the other hand, chucks of that thread are common from the importers and on eBay.

Doc.

 

[Provincial]

In my old Atlas catalogs from the 1970's, the spindle thread on the 618 was listed as 1"-10 tpi. I believe that early production threads may have been different, but still 1" major diameter.

Edit: According to Lathes.uk, the early thread was 8 tpi, so you have an early production lathe.

 

[bmwrd0]

That lathe spindle (six inch Craftsman or Atlas 618) is threaded for 1"-10tpi while early ones are 8tpi, so if you do go looking to source a new chuck, make sure that you know which ones you are getting and which you need. I believe that MyMachineShop.com or LittleMachineShop.com sell the backplates,

 

[motorick]

Thanks all. My lathe has the Timken bearings which I assumed made it a later model... but the spindle is definitely a 8tpi

 

[motorick]

fyi, I finally got the chuck 'open' using a 24mm socket & BFH. In case anyone is interested here is what the internals look like