Another Norton Newbie question!

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Frank you are a wealth of information! Glad you are on the list.

John, get yourself a decent thread pitch gauge and measure the tapped hole or old bolt. I believe you will find 99% of any bolts on a Commando will be either SAE (UNF, UNC); CEI (BSC) 26 TPI; or BA (small cap screw). British standard fine (BSF) and Whitworth threads (BSW) are rarely used on a Commando if at all.

Whitworth wrench sizes fit all hex heads for British thread form fasteners. Of course occasionally you will find a close fit with an SAE inch-size or a metric.

I find a decent set of Whitworth combination wrenches and sockets are a must, along with the usual SAE selection. Kokon, Japanese made sockets are relatively inexpensive and decent quality and Acesa, Spanish wrenches are well made for the hobby user. I find that Snap-On sockets are too thick to fit over certain hex bolts such as cylinder head bolts, but the slimmer Kokon fit nicely.
British standard fine (BSF) and Whitworth threads (BSW) are rarely used on a Commando if at all.

Ron L

Fastener lists say otherwise!
Again I refer to the Norvil list.

Here's a few examples:


Rocker spindle cover bolts
Timing cover screws
Oil feed union bolt
Fork stay bolts
Fork drain screws
Fork bridge studs
Carb manifold to head bolts
850 Mk3 gear lever bolt
850 Mk3 primary case screws


Head steady to cylinder head screws
Rocker oil feed bolts
Gearbox drain bolt
Gear lever bolt

Thank you for the excellent information on thread forms; it was certainly insightful. I never realized the hodgepodge of threads that the British used for assembling motorcycles.

I found this web site to be interesting and it tracks with what you were saying about the diabolical British fasteners.

"History of Whitworth" Well that explains it.

My Lord, no wonder I am so confused, it's not me it's the whole industry.
Like he said, he couldn't possibly make that stuff up.

Good Luck.......
More threads than you can shake a stick at! :lol:

Great info! And I used to think there were only two types on a Norton - "whitworth" and "american" :wink:


I stand corrected. I really wasn't considering the special fasteners like the banjo bolts and drain screws. But I have used 1/4-20 stainless allen bolts (UNC) for timing cover screws and MkIII primary screws and rocker spindle covers. These are relatively unstressed fasteners and the difference between the 55 degree and 60 degree threads have never given me a problem in over thirty years.
Possibly we have all got a slightly better understanding of the multiplicity of fastener types used on not just Commandos but British bikes in general?

Perhaps when Jerry updates the website it may be possible write up a list that gives the sizes and thread form information of a large number of these fasteners used on Commandos ?

Worth considering maybe?

I think it would be great to update the website with a comprehensive list of thread profiles/types used on Norton motorcycles. Jerry are you listening?


I, too, am guilty of using 1/4"-20UNC 2A threads in place of some of those goofy 55 degree British threads. In fact, up until now, I never new there was a difference betwixt the two! The 1/4-20s seem to work ok, though.
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