Today I was given a box of rusty thread taps, so I cleaned them off to identify them to see if they are any use on my BSA or Norton.
I do struggle a bit with identifying imperial threads, and see on this sites thread chart Non Standard Cycle Thread. What is that? I cant find any information on it and it is not listed on any thread charts that I can find. Can any of you enlighten me? Thanks

Some of the taps in the box are date stamped with dates that are WW2 years and have the MOD crow foot stamped on them

email (option): gasboy@btinternet .com

Peter, I have a nice chart with all thread types (well, nearly all....) and I'll send it to you.
You will see that the Cycle thread is not only 26tpi, but also can be 40, 32, 24 and 20!
This is a copy of a copy, so you will need some guessing and interpretation skills

email (option): viaconsu # planet dot nl

Thanks Hans, I have received it.
So am I right in thinking non standard cycle is the same 60 degree angle as cycle thread, but in the larger and smaller diameter threads has more or less TPI?

email (option): gasboy@btinternet .com

Hi Peter..You can find the information on the net if you Google British Standard Cycle Thread.
In the M20 context the less common pitches are used in a number of applications. If you come across an unusual pitch for the diameter on the bike it is likely to be one of these. A set of thread gauges in Imperial thread form (in conjunction with the relevant thread data) is a very useful tool in the workshop and well worth acquiring to help in identifying what you are looking at....Ian

email (option): ian@wright52.plus.com