Thread types used and warnings/alerts

quawk

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Jan 1, 2024
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Having just posted about Andover Norton and it's origin and association to Norton motorcyles, have been peering over their website about not only their vast parts availability, but also all of their technical info they provide. Have read the info they provide about the various thread types used on the Norton motorcycles.Besides the four different British based thread types, plus even metric in the Lucas switchgear, they list that have been used in the past, I see that in some of their replacement fasteners they offer that some of them are listed as fractional inch fine and coarse sizes. Long ago before ever having owned a British bike, I'd heard the term Whitworth and knew that that was a different thread/fastener besides SAE fractional inch and/or metric, that was used on Brit bikes. I had assumed all threaded fasteners and assemblies on the Brit bikes utilized this mystical Whitworth thread Now owning a Brit bike and doing more and more research on many various aspects of repairing one of these bikes am finding out that Norton used all of these various thread types. I realize that members here that have been working on these bikes for a long time have come to know this and know where the various thread types are used. But to a newbie, like me, as it says in the AN tech article it can be/is confusing. Was suggested in my first post when I was still on the fence about purchasing this bike that one thing I'd need is a set of Whitworth wrenches. Although I haven't had to get real deep into tearing this bike apart yet, so far anyway I've gotten by with the tools I already have. Have been keeping and reusing all original fasteners and putting them back where they came from. But can someone suggest or advise about any repairs or procedures where I should be paritcularly careful/observant about fasteners and threads on these bikes.
 
quawk said:
Having just posted about Andover Norton and it's origin and association to Norton motorcyles, have been peering over their website about not only their vast parts availability, but also all of their technical info they provide. Have read the info they provide about the various thread types used on the Norton motorcycles.Besides the four different British based thread types, plus even metric in the Lucas switchgear, they list that have been used in the past, I see that in some of their replacement fasteners they offer that some of them are listed as fractional inch fine and coarse sizes. Long ago before ever having owned a British bike, I'd heard the term Whitworth and knew that that was a different thread/fastener besides SAE fractional inch and/or metric, that was used on Brit bikes. I had assumed all threaded fasteners and assemblies on the Brit bikes utilized this mystical Whitworth thread Now owning a Brit bike and doing more and more research on many various aspects of repairing one of these bikes am finding out that Norton used all of these various thread types. I realize that members here that have been working on these bikes for a long time have come to know this and know where the various thread types are used. But to a newbie, like me, as it says in the AN tech article it can be/is confusing. Was suggested in my first post when I was still on the fence about purchasing this bike that one thing I'd need is a set of Whitworth wrenches. Although I haven't had to get real deep into tearing this bike apart yet, so far anyway I've gotten by with the tools I already have. Have been keeping and reusing all original fasteners and putting them back where they came from. But can someone suggest or advise about any repairs or procedures where I should be paritcularly careful/observant about fasteners and threads on these bikes.
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In the late 60s the British manufacturers started switching to American/SAE/Unified/Fractional or whatever you choose to call it. Norton was mostly switching to UNF and some UNC. None of them completed the switch. Most of a Commando other than the engine and gearbox is UNF/UNC. The gearbox is all British. The engine is a combination. I am aware of no factory metric in a Commando or Triumph before 1976 including in anything Lucas or Amal. For instance, the handlebar consoles at least before 1975 used #10 (don't remember if 10-24 or 10-32).

A good overview is here: https://britishfasteners.com/help.html You can lookup fasteners by part number here: https://gregmarsh.com/MC/FastenersList.aspx to find the thread size (usually).

We tend to call all British threads Whitworth (BSW) - there are almost no Whitworth fasteners in a Norton! The screws for the rocker spindle covers are 1/4 BSW but since 1/4-20 (UNC) is the same size and thread count, the wrong screws are often there. BSW has 55 degree angle threads where UNC has 60.

To answer the question in your last sentence - ALL!
 
L.A.B. said:
Unified (since 1949) not SAE.
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Yes! We need auto correct :)

We call them all kinds of things - about like calling all British threads Whitworth.

Another fun thing: Ask Americans what SAE means - many will say American! I even had an actual mechanical engineer tell me "Standard American Engineering"
 
Wherever you can put in American bolts. I usually tap the threads in the gearbox inspection cap for american. If I remember right it is 10 - 32.
 
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