Bolt Thread compatibility
Bolt Thread compatibility
(OP)
Hi All,
Does anyone know if a BSW (british standard whitworth) bolt can mate with an UNC nut or vice versa?
I looked up charts and found that the threads per inch (TPI) for BSW bolts and UNC bolts are the same for all sizes except for 1/2" size.
Does anyone know if a BSW (british standard whitworth) bolt can mate with an UNC nut or vice versa?
I looked up charts and found that the threads per inch (TPI) for BSW bolts and UNC bolts are the same for all sizes except for 1/2" size.





RE: Bolt Thread compatibility
Cheers
Greg Locock
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RE: Bolt Thread compatibility
Our problems were we tried to mix and match instead of dumping the Whitworth studs. This episode did one thing as it convinced the chemical side of the road to spin on the nuts and supply a stud and nuts togather like the fiber side had been doing for years.
Even to try this with materials that will gall will cost you money.
RE: Bolt Thread compatibility
RE: Bolt Thread compatibility
It makes me wonder similar things as to what happens with this 'locking" thread
http://www.spiralock.com/technology
Dan T
RE: Bolt Thread compatibility
I worked this out. The to-specification thread profiles interfere.
I was very surprised to find out that camera tripod attachments are 1/4-20BSW, not 1/4-20UNC. This actually makes sense when you remember that tripods predate the Unified National standard. We stick 1/4-20UNC screws into these things all the time. I do not really know if modern cameras and tripod screws still are BSW, or if they are extra sloppy to allow more clearance.
Camera tripod do not engage very many threads. I do not think I have seen a tripod mount that violates unclesyd's conditions, above.
RE: Bolt Thread compatibility
tmoose,
Here are two of several papers from the old NASA.
The most impressive use for the thread form is used on fasteners that hold the Shuttle's main engines on and can be reused. I can see no worse case. We use them on some high speed equipment due periodic periods of instability excursions.
http:
http:/
RE: Bolt Thread compatibility
Also, tripods will be attached to "something precious" only "finger-tight" so as soon as binding occurs, the camera is considered tight and the motion stopped by the user. Who is usually pretty cautious anyway about his camera or laser.
RE: Bolt Thread compatibility
A lot depends on the class of fit, of course, but in experimental tests I've found that Whit and UNC will run right up in all sizes from about 1/4" to an inch or larger, other than the 1/2" with its different TPI. But it should never be done for real!
The difference in thread angles, mentioned above, is the problem. Putting 55 and 60 degree threaded components together with cause the load to be taken on the crest of the thread rather than fully on its flank, and there is a very good chance of fretting and loosening to follow.
My regular Whitworth experience is on historic steam railway locos and I never mix the threads (though I've had a few near misses!) but I have heard of problems with mixed Whit/UNC fasteners coming loose on motorbikes.
David W.
Mechanical Engineering Group
Nene Valley Railway
RE: Bolt Thread compatibility
David W.
Mechanical Engineering Group
Nene Valley Railway