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Hi Christian

26 tpi would be cycle thread BSCY 9/32 is a strange size bicycle crank cotter pins used to be that size

Regards Roger

The measure 9/32 "(7,143mm), 26 threads per inch corresponds to the BSF system (British Standard Fine).I find it strange, but I do not rule it out.

Greetings Gerardo ....

I have a feeling that 9/32" BSC screws are the same size as those used on Dominator Twin rocker adjusters.

..... another bit of irrelevant information - also the thread on pre-war rear brake adjuster rods.

BSCy it is, attached a useful reference.

Attachments
bs-cycle-threads-jpg

Even more irrelevant, BSC 9/32 is close to the quite unusual thread M7. Which has 25,4 tpi.

Why not use 7mm x 1.0 pitch bolts? They are only 4 thou smaller in diameter so only 2 thou smaller on thread depth than 9/32 and taps and dies are readily available and not very expensive. At a pinch you could tap the pump to 9/32 x 26 and still use a 7 x 1 bolt. In one inch of engagement it would only be out .6 of a thread and as it is minutely smaller would probably screw in at least half to 3/4 of an inch. This post will be too late to help Christian but may help others.

P.S. 7 x 1 bolts are available from your friendly Honda dealer they are rear chain adjuster bolts for CB400 fours and about 2" long from memory.

C'ya Bill 

Bill has a good point about where to find M7 bolts, because(annoyingly) M7 is a non-preferred size.  M6 and M8 are easy to find.  M7 is used in mass produced machines, since if you make tens of thousands it is worth going non-standard, but otherwise they are hard to find.  Incidentally: if you want a correct looking wing nut for rear brake adjuster, you can use the NOC wing nut which has 1/4" (post war maybe?) thread, and drill it slightly and tap 9/32".  But first find your 9/32 tap...

Bill, also the degrees of inclination of the thread steak further favors the metric adjustment of 7mm (60º against 55º).

Greetings, happy holidays , Gerardo

At this size BScy and BSF are identical 

I had to buy the special taps when I made rockers for my flat tankers but I second the possible use of M7 x1 for your use.