Threading of mounting bolt on old caliper brakes

[rogerzilla]

It's 1/4", but does anyone know if it's BSC or BSF?  The brakes are GB (Gerry Burgess). 

[aeolus]

Though that size (1/4") was the same - 26tpi - with a virtually identical thread engagement - one of only a couple of sizes that match.

Fitted any of the bushes as yet ?

[rogerzilla]

Though that size (1/4") was the same - 26tpi - with a virtually identical thread engagement - one of only a couple of sizes that match.

Fitted any of the bushes as yet ?

There's a small, possibly irrelevant, difference in thread angle.  The blessing and the curse of British threading is that each was designed to be the best for one job, so there is a plethora of different ones: BSC, BSF, BSW, BSP, BA (which is metric!), yadda yadda.  And that's without the US standards UNC, UNF, etc.

I'm avoiding stripping down the TSR until the F-frane is 100% reliable.  Maybe later this month. 

[aeolus]

Yes I know the thread angles are different 55/60 deg - but with threads that 'have lived a life' they are probably well worn already !

I have 1/4 BSF taps of various vintages ! (along with lots of taps/dies for many of the threads you note ) I could pop one in the post so you could run it through if you still have the nut or compare bolt under a glass etc.
OrI could knock up a nut to try but I'm not sure what steel hex stock sizes I currently have, so it would be as found !