Check Out My Mill Drawbar

D

ddickey

H-M Supporter - Gold Member
H-M Supporter Gold Member
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Apr 21, 2016
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My drawbar is 5/8-11 but check out this smaller section which is 1/2-12.
Does anyone have an idea why this is?
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What type of collets/ toolholders does it take?

My horizontal mill drawbar is made like that so it can take NMTB 50 or 40 with an adapter...

-Bear
 
40 taper. NMTB 40 is the proper but cat 40 work fine also.
 
The drawbar may be designed to take a 30 with a sleeve adapter...

-Bear
 
Funny timing. I like it!!

Today I couldn't find my large drawbar. I rarely have to use it.
Your drawbar would have been great to have.
 
1/2”-12tpi is a old pitch, not seen much since 1/2-13tpi became the USS standard
 
I've been researching. 1/2-12 is/was a whitworth thread, some call is a bsw thread. Apparently 1/2-12 was quite popular in the US years ago.
I was reading and a guy was talking about his MT3 collets that had a 1/2-12 thread. So, If you had an NMTB40 to MT3 adapter this bar I have might work although it might be troublesome getting both to tighten at the same time. I found two mt3 tools that were 1/2-12. Looked like low quality tools so not sure what the manufacturer was thinking but I may just shoot them a call next week to ask.
 
Looking at a SYIC product pdf and they offer NT30 toolholder's w/a 1/2-12 drawbar thread.
 
ddickey said:
I've been researching. 1/2-12 is/was a whitworth thread, some call is a bsw thread. Apparently 1/2-12 was quite popular in the US years ago.
I was reading and a guy was talking about his MT3 collets that had a 1/2-12 thread. So, If you had an NMTB40 to MT3 adapter this bar I have might work although it might be troublesome getting both to tighten at the same time. I found two mt3 tools that were 1/2-12. Looked like low quality tools so not sure what the manufacturer was thinking but I may just shoot them a call next week
Click to expand...

ddickey said:
I've been researching. 1/2-12 is/was a whitworth thread, some call is a bsw thread. Apparently 1/2-12 was quite popular in the US years ago.
I was reading and a guy was talking about his MT3 collets that had a 1/2-12 thread. So, If you had an NMTB40 to MT3 adapter this bar I have might work although it might be troublesome getting both to tighten at the same time. I found two mt3 tools that were 1/2-12. Looked like low quality tools so not sure what the manufacturer was thinking but I may just shoot them a call next week to ask.
Click to expand...
The USA 1/2 12 was not a Whitworth thread, which is 55 degree with rounded crest and root, it was a standard 60 degree thread with flat crest and root, the 13 tpi thread was adopted because the 13 pitch made the root diameter larger and stronger.
 
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