AJS & Matchless Owners Club

Good morning,

Information re thread size of stud please, ( 4 5/8” long, 5/16 diameter, engine to frame mounting ). I thought it was 5/8 BSF, wrong. My thread sizing skills are not too sharp I’m afraid! Need some new nuts ( for the stud, that is!)

Thanks,

Steve

5/16" cycle thread 26TPI. Most sizes are in the parts lists up until about 1957 or so. After that you only get the part number. You need to get some thread gauges and you can download a chart of thread sizes or get a Zeus book with everything in.
Dave.

Presumably for a '55 G3LS.

26 tpi

See spares list page 8 here:

http://archives.jampot.dk/book/Spares_l ... ingles.pdf

Hi both,

Sorry, just realised didn’t state machine! Correct, the ‘55 G3LS . I have a thread gauge and the original Zeus book. My skills on the gauge leave much to be desired, that’s how I ended up with 5/8 BSF. My gauge is Metric and BSW only, presumably a gauge to measure cycle thread sizes needed?
Thanks, now have the information required.

Steve

Hi

The BSW thread gauges will have the relevant pitches for cycle thread, (BSCY), but in general BSCY threads are 26 TPI until around 7/16" when it changes to 20 TPI. The changeover point is not fixed so you need to check rather than assume.

I find this list invaluable for identifying fasteners:

http://archives.jampot.dk/technical/Spe ... ashers.pdf

It's not totally comprehensive and the data is availbla elsewhere, but here it's collated pretty well into one document.

Regards Mick

Hi Mick,

Thanks for the information, I have opened the link and copied data into my information folder. Very useful. I just wonder why they didn’t stick to one system? Was there a logical ( or maybe illogical) reason why they ( AJS/ Matchless ) didn’t?

Thanks again,

Regards,

Steve

G3L1946 wrote: ↑Tue Aug 03, 2021 4:04 pm I just wonder why they didn’t stick to one system?

Hi

Essentially they did, pre hybrid AMC bikes use BSCY threads throughout with the exception of threads into aluminium castings, (which tend to be BSF).

Early bikes may include BSW threads but the over riding trend is to BSCY, (CEI).

A set of Whitworth thread gauges and a means of measuring thread diameter will identify all the threads encountered.

Regards Mick

Hi Mick,

Interesting, learning something new on each visit!

Thanks,

Regards,

Steve

That's a great resource, Mick D. Somewhere in Christian's archives there's a spreadsheet for tis as well which I've found invaluable but I don't have a "clean" copy, it's full of my own notes.

Johnny B

56G80S wrote: ↑Tue Aug 03, 2021 7:58 pm That's a great resource, Mick D. Somewhere in Christian's archives there's a spreadsheet for tis as well which I've found invaluable but I don't have a "clean" copy, it's full of my own notes.

Johnny B

Hi Johnny / any other spreadsheet wizard

I downloaded that SS some time ago but couldn't work out how to stop some of the part numbers being converted to dates, any advice?

Regards Mick