3 jaw questions

Has the backing plate ever mounted on the spindle correctly? , if not have you checked it with a thread gauge, hardening has 2 1/4 x 10 tpi spindles they look close. Been there with a spindle thread protector, just sayin
 
Has the backing plate ever mounted on the spindle correctly? , if not have you checked it with a thread gauge, hardening has 2 1/4 x 10 tpi spindles they look close. Been there with a spindle thread protector, just sayin

The lathe is 1980s Jet(Taiwanese) 12x36 belt drive, 2 1/4x8 threads; 2 chucks and a face plate I have install easily. I picked up the chuck in question when I just got a 1991 12x24 Chinese lathe, same thread as measured with a thread gauge. The chuck mounted correctly(slightly snug ) on the lathe I was given as does a face plate(easily), which also mounts correctly on my lathe.

I'm thinking the threads may be slightly dimensionally different. If I had a tap that size I'd use it, I think that's the best option but don't have one. I'll get in my shop this evening and try some and try some of the suggested fixes.

thanks, Brian
 
You can remove the backing plate from the chuck . It'll be easier to do then spinning all that on your lathe . It's only about 4-6 bolts usually. Plus you can clean the chuck repair and relubed as needed. I wouldn't mount it in the four jaw with the chuck mounted . Just my opinion.
 
Also, you can put the Dykem on it then work it on to where it binds. Then look at it closely to see where it is binding., But agree with Dlane as unless it has fit prior it may be a little diff thread, I know the Jet 10x24 I have is a Metric size with a 8 tpi Kinda diff and hard to find.
 
You can remove the backing plate from the chuck . It'll be easier to do then spinning all that on your lathe . It's only about 4-6 bolts usually. Plus you can clean the chuck repair and relubed as needed. I wouldn't mount it in the four jaw with the chuck mounted . Just my opinion.

I'll remove the backing plate, marking/indexing the plate and chuck for reassembly.

Also, you can put the Dykem on it then work it on to where it binds. Then look at it closely to see where it is binding., But agree with Dlane as unless it has fit prior it may be a little diff thread, I know the Jet 10x24 I have is a Metric size with a 8 tpi Kinda diff and hard to find.

Dykem is a good idea. The thread is definitely 8tpi as measured by a thread gauge, the difference(if the problem is thread size) is most likely a few .001s.

Brian
 
after you remove the backing plate try to tread it on back wards, more than likely the thread is a little under size in the chuck. You may be able to lap it in with valve lapping compound, i had on years ago that did the same thing.
 
I think I have a tap and die in my shop that size , I watch for them on eBay the die I got for $20. If I remember right new not used hss too. I bought them to help make adapters for my logan . I want to make several , er collet 32-40 , Jacobs lathe chuck from an atlas #20 size it's threaded 1 1/2 - 8 . I have it so why not use it.
 
after you remove the backing plate try to tread it on back wards, more than likely the thread is a little under size in the chuck. You may be able to lap it in with valve lapping compound, i had on years ago that did the same thing.

Backing plate will not go on farther than a few turns from the back, about the same as from the front. Given this it seems most likely that the chuck is undersize. Any one have a 2 1/4" 8tpi tap they want to rent me? On the other hand it may be best to instal a new backing plate.

thanks, Brian
 
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Do me a favor and measure the openings etc on that backing plate. It almost sounds like it fits my 10X24 If so I would possibly like to purchase it off you. It sounds like it is the metric size X8 that fits mine. Then you could put a new one on the chuck.
 
Do me a favor and measure the openings etc on that backing plate. It almost sounds like it fits my 10X24 If so I would possibly like to purchase it off you. It sounds like it is the metric size X8 that fits mine. Then you could put a new one on the chuck.

I googled metric size X8 but didnt turn anything up. Where can I find info on it?

Brian
 
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