Author Topic: A7 engine nut size - drive sprocket  (Read 466 times)

Offline TassieChris

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A7 engine nut size - drive sprocket
« 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

Online bsa-bill

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Re: A7 engine nut size - drive sprocket
« Reply #1 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
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline mikeb

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Re: A7 engine nut size - drive sprocket
« Reply #2 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!
New Zealand
'61 Super Rocket  - '47 B33 -  '18 Triumph Street Triple RS

Offline TassieChris

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Re: A7 engine nut size - drive sprocket
« Reply #3 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.

Offline muskrat

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Re: A7 engine nut size - drive sprocket
« Reply #4 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
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7