Spindle thread on SB 9"

[craptain]

I have had my 1937 South Bend for several years. During that time I made a new backing plate for my new chuck. Then I picked up a Jacobs Flex-collet chuck which didn't quite fit. I planned on cleaning up the thread a bit but never got round to it. Fast forward to last month and I picked up a 1957 9A. This is going to replace the early model, but I want to keep the newer chuck and other parts. So I start by swapping chucks and find that the chuck from the newest machine is a very tight fit on the old machine. Get the collet chuck and it fits perfectly on the newer machine. Same story with faceplates, drive plates etc. So did sizes or tolerances change over the years? Everything fits the new lathe but not easily for the reverse.

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[songbird]

I have had my 1937 South Bend for several years. During that time I made a new backing plate for my new chuck. Then I picked up a Jacobs Flex-collet chuck which didn't quite fit. I planned on cleaning up the thread a bit but never got round to it. Fast forward to last month and I picked up a 1957 9A. This is going to replace the early model, but I want to keep the newer chuck and other parts. So I start by swapping chucks and find that the chuck from the newest machine is a very tight fit on the old machine. Get the collet chuck and it fits perfectly on the newer machine. Same story with faceplates, drive plates etc. So did sizes or tolerances change over the years? Everything fits the new lathe but not easily for the reverse.

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I’ve had several SB 9a’s through the years. There is a a section of the thread spindle that is slightly oversized, to allow the chuck to register correctly. Double check that section. Your older lathe may be worn, the newer one may be slightly dirty. Hope this helps, Jim

 

[craptain]

I’ve had several SB 9a’s through the years. There is a a section of the thread spindle that is slightly oversized, to allow the chuck to register correctly. Double check that section. Your older lathe may be worn, the newer one may be slightly dirty. Hope this helps, Jim

I could understand that. But the older lathe appears to be slightly larger, rather than worn smaller. In fact the major diameter of the thread is .003 smaller on the newer machine. Other measurements are within .0005

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