The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: TassieChris on 31.05. 2016 09:15

Title: A7 engine nut size - drive sprocket
Post by: TassieChris on 31.05. 2016 09:15
Hi Guys
I'm hoping someone can help me identify the size of the thread shown on the pictures below.
The nut is stripped so I need to buy another but I'm not sure of the size.

Pretty sure its 3/8 (measures .37 inches on my vernier) and the closest thread gauge I have makes it about 27 TPI (probably 26 TPI but I don't have a 26 TPI gauge).

The closest thread I can find is a 3/8 cycle engineers thread which is 26 TPI with a 60 degree angle or there is also a brass pipe screw thread which is also 26 tpi but with a 55 Degree angle on the thread.
My guess is its a cycle engineers thread but I was hoping someone could verify that for me.

Thanks
Title: Re: A7 engine nut size - drive sprocket
Post by: bsa-bill on 31.05. 2016 09:56
Shaft and idler on Ebay - £40 ish with postage  (looks in good nick might even be someone here)
enter in the search box - BSA A7 A10 CAMSHAFT DRIVE IDLER PINION & SHAFT - and it should take your there.

However I'm sure it's cycle
Title: Re: A7 engine nut size - drive sprocket
Post by: mikeb on 31.05. 2016 12:00
its too cold to go outside, so parts book says for all A group dynamo driving sprocket nut = 2-449 and according to someones spreadsheet of bolts its:
02-0449   NUT   CEI   3/8"-26   THIN HEIGHT

so you were right!
Title: Re: A7 engine nut size - drive sprocket
Post by: TassieChris on 31.05. 2016 12:50
Thanks Guys - that helps a lot.
My shaft is actually fine its just the nut that's stripped so hopefully now I know what it is my local "nuts and bolts" shop should have one.
Title: Re: A7 engine nut size - drive sprocket
Post by: muskrat on 31.05. 2016 14:15
G'day Chris.
Go to the local pushbike shop and get a 3/8" axle nut. that's whats holding mine on.
Cheers