Hi all

Found these in a joblot of taps & dies but have been unable to identify them.

The goid kadies of Google keep saying they are gas threads, which I very much doubt

The smallest 17g is about 1/16th and the latgest 12g is about 5/32.

Anybody have any ideas

Thanks

Spoke threads? G would be gauge not gas.

What is the tpi.

Edited By JasonB on 17/07/2021 17:29:35

German for ‘thread pitch’ is

Gewindesteigung

MichaelG.

I'd take a piece of round brass bar close to one of them, cut a thread, measure its TPI with a thread gauge, measure diameter then look at thread tables? Once you figure one out, the others should follow. It could always be some strange thread form though. If you don't identify them you can't use them.

I think spoke threads are rolled and not cut for strength

More Bradbury's spoke thread dies in this thread

If they are not spoke threads then they are likely BSC cycle thread as the smaller sizes of those used a gauge number rather than size and pitches were a lot finer than the usual 26tpi associated with BSC threads. Have a look at page 40 & 41 of this pdf

The "16g 62" is the right tpi for a 16g spoke thread

CEI is the precurser again 16g is 62tpi and used for spokes, etc

Edited By JasonB on 17/07/2021 20:57:11

Could it be significant that both Bradbury and Leinnum are ancient makes of sewing machine?

C.1920s BRADBURY NO.1 VINTAGE CAST IRON BICYCLE/ MOTORCYCLE SHOP SPOKE ROLLER

And another, not drive pins that fit the holes in the die

Edited By JasonB on 18/07/2021 07:44:41

I've had a set of dies like the OP's for longer than I care to remember. Always assumed they were wire spoke thread sizes. A couple of them definitely are as I have run them down threads rolled by my "Cyclo" spoke thread roller.

Thanks for all that info.

Very enlightening. Just goes to show how innovotive the early engineers were.