22g thread size - 5/16 Bsf

[robbsa]

Hi All,

Maybe being really stupid here, but unfortunately i'm of the metric generation, so need a little help! the needle jet on my carb is not as the standard one from Amal, the bore that it fits into is larger than the fit they provide. Its on a type 5 carb so only run for a very short period of time so could have been originally like this or could have been modified at some point to fit a home made jet.

Anyway, the thread on my jet measures at 22G on my thread gauge that i have just purchased off ebay. 22G! whats this! is this refereeing to the TPI, really annoying as all the other sizes give the fractional measurement next to it too. I believe from looking on the internet that this may be a 5/16 bsf thread. Can anyone confirm.

thanks

Rob

[Goldy]

Rob I don't know about the G but in engineering usually stands for gauge as in standard wire gauge, so possibly referring to thread pitch gauge. 22 TPI is 5/16"  BSF as you say. All the best Goldy

[twolitre]

Rather puzzling this. Seems a strange thread gauge. Would it not be easiest to see whether the thread on the jet fits a 5/16 B.S.F. nut (or any other known nut for that matter)?

[RichP]

I suspect that you've got a German-made gauge. Are all the 'threads per inch' sizes marked 'G' ? It indicates threads or turns in this context.

If you count the ridges against a rule, you should find that it has 22 per inch (22 gang).