Looking for two 1/4 x 20 tpi by 1-1/4" (or longer) countersunk allen head screws/bolts - any suggestions?
(I think that's UNC? or maybe BSW? Are they interchangeable? I never got the hang of that)
Thanks,
-- Peter Fairbrother
Screws?
Apr 26, 2010
5 Replies
--Sounds like SAE to me; 1/4"20 is National Course thread. Proper name for the head is socket flat head machine screw.
I've got a box (100) full of 1/4" 20tpi BSW CSK head screws. only problem is they're 1/2" long and cross head. I needed 8 for a job :-(
Mark Rand RTFM
There'a a current advert in homeworkshop.org.uk for 1/4" BSF screws.
No they are not interchangeable. BSW is 55 degree thread form, UNC is 60 degree. Shortening is also different BSW is H/6 major and minor, while UNC is H/8 major and H/4 minor for external thread.
I believe 1/4 x 20 BSW is standard small camera tripod socket thread if that provides a convenient gauge.
That doesn't help you with a source though. I've got a note of this place as a source, but I have never had to use them so no idea of the minimum order qty
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Alan
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