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+--- Thread: checking dies (/showthread.php?tid=3656)
checking dies - JonE - 17-12-2019
Just picked up a few dies from the closing-down secondhand tool shop, and I had 3/8" 26 and 1/2" BSC 26 down on my wants list from some good A7 list on the web.
I now have a die marked 1/2" 26 which was in the BSB drawer.... but there are no marks to confer what it is. Can a 1/2" 26 be anything else other than what I need?
Ditto 3/8" 26 - marked BSB on the die but in the list it just said 'special'...
In the shop they suggested there may be differences between BSB and BSC, but how would anyone actually know if its not marked on the item?
Hope someone can elucidate...
RE: checking dies - Ian McGowan - 17-12-2019
I am no expert Jon but, I believe that 3/8" x 26TPI is a British Cycle thread (60 degree thread form) see here
http://www.oldengine.org/members/diesel/Tables/cycle1.htm
I also believe that 1/2" x26TPI is a Model Engineers Standard thread (Whitworth form) see here.
http://www.oldengine.org/members/diesel/Tables/me1.htm
Equally, both could be Brass Pipe Screw threads, (whitworth form, 55 degree thread angle. All British Pipe screw threads from 1/8" to 1-1/2" are 26 TPI. see here.
http://www.oldengine.org/members/diesel/Tables/brass1.htm
I can only suggest that you find someone with a comprehensive set of thread gauges and who knows how to use them.
RE: checking dies - Parazine - 17-12-2019
British Standard Cycle (BSC) uses 26 TPI for all threads 1/4" and over. It is a 60 degree thread form.
British Standard Brass (BSB) always uses 26 TPI in sizes from 1/8" to 2". It is a 55 degree Whitworth thread form.
In practice, almost interchangeable, although purist will howl!
RE: checking dies - JonE - 17-12-2019
Thanks both - that's good enough for me! Good enough for clean up of threads.
The purists can howl, but they can direct their spleen on the toolmaker for not writing the full spec on his or her wares! I do have a big thick wad of gauges somewhere from ebay china, but its unwrapped and will probably stay that way...
RE: checking dies - Paulinos - 17-12-2019
Can those gauges from eBay China stay that was for a long time without any issues?
RE: checking dies - Nick Lettington - 17-12-2019
Jon E's thread about dies got me to wondering... If BSB is a thing, do our wheel studs have a BSB thread in order to utilise brass wheel nuts, or am I over thinking this? It might explain why the special nuts I had made for my Speedex alloy wheels were so very tight on the studs...
RE: checking dies - Austin Carr - 17-12-2019
Information on British Standard Brass:-
https://britishfasteners.com/threads/bsb.html
RE: checking dies - Ian McGowan - 17-12-2019
Nick, you are over thinking it. BSB was used only on brass tubing.
RE: checking dies - Nick Lettington - 18-12-2019
(17-12-2019, 08:27 PM)Ian McGowan Wrote: Nick, you are over thinking it. BSB was used only on brass tubing.
Thanks Ian... That's good to know... I'll run a tap and die over both to ease them... But it does mean someone or others thread cutting is not up to par!
RE: checking dies - Bob Culver - 18-12-2019
The cycle threadform is unusually shallow. Hence I have asked before if supplied modern spokes and nipples have true cycle threads. Or if any dies or taps for cycle 6 gauge available, but no answer.
And Nick the brass are al 26 tpi which does not corres with 3/8 BSF. it may not apply to old BSF stuff, but many of the cheap taps and dies available today are of vary varied size.
Two piece dies have unfortunately gone out of fashion, but unless used carefully produced way out of size.