Mystery Thread?

randyjaco

randyjaco

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I am working on an old Jet (Taiwanese ) lathe. The lathe is composed of a confusing mixture of imperial and metric fasteners. One of the exposed gear spindles has a male thread that I can't figure out. In inches the thread is .501" - 11 1/2 TPI. In metric it is 12.68mm - 2.0 thread. I can't find a M13 thread anywhere locally, and the same is true for a 1/2"- 11.5 nut. A M12 or M14 -2.0 will nor fit nor will a 1/2"-13. The metric and imperial thread spacing measurement as very close but not dead on. Before I make a custom nut, am I missing something?

Randy
 
I am wondering if it might possibly be a british whitworth thread. The 1/2" diameter in those is a 12 pitch.
 
according to the thread gauge, it is closer to 11 1/2 than 12
Randy
 
This is a threaded stud for a gear?

Just a thought, maybe it is a tapered thread. Iirc one the BSPT is 11, and I think one of the larger NPT threads is 1.5. A tapered thread saves a few pennies on locking nuts.

If that is an 80's Jet machine, then it will be a bit of a cludge. That was when Taiwan was still making low end cheap stuff, and Americans where doing full resistance to metric. There was a ton of metric thread with imperial wrench sizes kicking around from that era.
 
I was looking in my stash for a 1/2-13 pulley tap on Sunday. Found a 1/2-11! The things that make ya wonder. Hmmmm.
I've not worked with Whitworth or much metric. You've very likely examined the Machinerys Handbook. She doesn't fall into specs even for a very tight 3A fit.
How old is she? Is it back before standardization? http://www.nord-lock.com/bolted/the-history-of-the-bolt/
Also, possible that it is very intentionally a proprietary thread.

Daryl
MN
 
Yes, it is a threaded stud for a gear. It is an 80's model Jet. (1340T). Best I can tell it is a 60 degree thread. I see no taper in the major or minor diameters.
Thanks for the responses guys

Randy
 
Know anyone with an optical comparator?
Daryl
MN
 
Supposedly some of those old Jet lathes had a mixture of metric sizes with SAE threads. :)
 
how does a 1.75 thread gauge fit. Some one in the past may have forced a 1/2-13 over an m12-1.75.
 
Mystery solved!
I went back an measured again. It is half - 12. Somehow I managed to overlook the 12 pitch gauge. I sure thought I used it, but obviously didn't 8(

Thanks for all the help.
Randy
 
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