Peculiar Threads - but UK

In message , Steve W writes

If nothing else, it would prevent stud and bolt being interchanged.

Except 5/16" is nowhere near 6.7mm.

Thanks for the link to the miniature threads page. The story on parsing sharp edged irregular holes is a new one to me:

Absolutely fascinating, thank you. The parser looks potentially useful, maybe one day I'll need to try it.

David

Assuming you really do mean 6.7mm (not 6.3mm ?) it must be 17/64 x 18 tpi ? Which would make it easily the oddest thread I've ever heard of. I've got a couple of 1/4 x 18 tpi threads to cut for some replacement parts for a telescope mount - the originals use that thread in preference to 1/4 x 20 tpi for no reason I can fathom.

Have a look at 5/16"

First one is 1/4 whit. Second one is 17/64" x 18 OK so it's special but you asked what it was. No metric is close either in diameter or pitch.

-- Regards,

John Stevenson Nottingham, England.

Visit the new Model Engineering adverts page at:-

Which is almost as helpful for single pointing it on a lathe!

Mark Rand RTFM

Bear in mind these are pre-WW1 and probably handcut. They are corroded making good measurement difficult, esp thread angles

Thanks John, you are probably on the money as the workshop the engine was made in did manufacture bicycles from scratch at the time the engine was built.

Steve