AJS & Matchless Owners Club

dodger wrote:They look coarse because the picture is blown up for clarity, that thread is most definitely 1/4 Bscy.

Apologies chaps. Specsavers apptmt way overdue!
Here are three 1/4 inchers - WW, BSF and BSC from l to r . .

Grovel grovel.

Are these bolts Cycle or BSF? My sheet implies BSF, but I'm not certain. Both are 26 tpi!

1/4" BSF and Cycle are both 26TPI and both of the Whitworth form - ie the threads are 55 degrees - so they are the same.

And thank you Laurence for the drawing - I've got to take the ones off that I made and shorten then - they're hitting the chainguard!

Cycle is actually 60° - same as UNF UNC and metric - no Specsavers faux pas for that! Both 26tpi at 1/4 inch, yes.
BSW and BSF are 55°.
1/4 Cycle and BSF can be interchanged, yes, but I wouldn't on a part that needs to withstand loads and stay done up. Hard to spot the difference between them though, especially if they're a bit worn.
Same issue with BSW and UNC, where the tpi is the same on several diameters but the angle isn't. And worse with 0BA and 6mm, where the angles are 12.5% different but the pitch is 1mm.

1/4BSF threads are also 3 1/2 thou deeper than 1/4 Bscy.

Well what about the nuts - anybody got any info on them?

I wonder if tihs stuff has been covered in the past? I'm sure I saw someting once. As this thread shows, a little knowledge (me) is a dangerous thing.

I generally find it really confusing. I've been having a tidy up and find a small poly bag with a receipt from Hawk Fasteners (who are really helpful to motorcyclists) with some UNC HT bolts and nyloc nuts in it. Why had I bought them, or the similar one with CEI stuff in.

I'm going to have to get some thread gauges.

Johnny B

As I listed under the G2 section VilliersServices.co.uk list these bolts at £1.74 each for the James and Barnett