Wierd tap and die needed - BSB or BSC

[Harv]

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

[ardiesse]

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

[Harv]

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

[ardiesse]

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

[Harv]

Many thanks.

Cheers,
Harv