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The dry sump pump for the meth monster has a cable tachometer drive, which I plan to use (with an old Jones tacho). The retaining nut for the tacho cable goes into a male brass thread on the tacho drive. The thread is wierd - 1/2” and about 27tpi. Too big and fine for NPT, BSP etc.

I suspect it is 1/2”-26tpi (my 27tpi thread gauge is close, and I don’t have a 26tpi gauge). This would make it either British Standard Cycle (maybe), or British Standard Brass (more likely). I’ll need to clean the male thread with a die, and may need to make up a nut (with a tap).

I’ve got some wierd taps and dies (and perhaps the worlds largest collection of Whitworth gear), but very few BSC or BSB gear. Anyone got a 1/2” BSB or BSC tap and die I can borrow? They are a little pricey for a one-off job.

Cheers,
Harv

Harv,

Way down in the dungeon at work is a pegboard with a series of dies, different diameters , but all the same pitch, about 27 tpi. I think these may have been used for electrical conduits or similar. The workshop guys have long since shut up shop today, but tomorrow I'll have a firkle around. If that doesn't come up trumps, I'll ask the guys in the machine shop. There's not much that they don't have.

Rob

Thanks Rob. The BSB die sets are like that - all different diameters, yet all 26tpi. They are made to thread brass tube that has a constant wall thickness irrespective of the pipes diameter.

I may have to make a “tube nut” to be made captive on the tacho cable. I found a jam nut in my stash last night (old instrument fitting), but it is not deep enough to hold a cable in place.

Cheers,
Harv

Harv,

Bingo. I found the 26 tpi taps in the workshop. Dies, however, seem to be lacking.
Give Graham Macdonald Services in Girraween a call. They have all the odd sizes of threading tools.

Rob

Many thanks.

Cheers,
Harv