Would someone be kind enough to tell me the correct thread size for the 5/16 front fork studs (4) which retain the front mudguard support bridge. They go into the ally lower fork leg and I guess they are either BSF or BSW.
Thanks
Barry
Previously Barry Robinson…
Previously Barry Robinson wrote:
Would someone be kind enough to tell me the correct thread size for the 5/16 front fork studs (4) which retain the front mudguard support bridge. They go into the ally lower fork leg and I guess they are either BSF or BSW.
Thanks
Barry
Hello Barry - I believe that they're 5/16 inch Cycle thread (26tpi) with a reduced head hexagon (1/4 inch BSF) on Dommies etc but UNC on Commandos and Mercuries. The very late 650SSes and last Atlases may also have switched. Cheers, Howard
Later bikes may well have…
Later bikes may well have used bolts as described but your Norton used studs and nuts. AMC changed all sorts of things , Bolts would be easier to fit and may make it less likely to squash the bridge while fitting and preload the forks which causes sticking /sluggish action.
Thanks for your replies. R…
Thanks for your replies.
Robert, I take your point about bolts being better as they would surely make it a lot easier to fit and remove the mudguard as its all very tight around there.
Although I wanted to keep this rebuild as close as possible to the original spec I think I might put bolts in there instead of studs.
Regarding the thread pattern I can't believe Norton would have used such a fine thread as cycle into ally, on an AMC it would have been BSW. Even BSF would be iffy.
Barry
Barry
Later bikes may have had U…
Later bikes may have had UNC threads in ally and unf into nuts. Or a bastard mixture!.
Previously robert_tuck wro…
Previously robert_tuck wrote:
Later bikes may have had UNC threads in ally and unf into nuts. Or a bastard mixture!.
In 1959 however it would have been Imperial and I'm trying to find out what thread it was they used then, someone must know surely? It won't be Unified.
Anyway thanks for your response.
Barry
Hello again Barry - I alre…
Hello again Barry - I already told you it's 5/16 inch BS Cycle (26TPI) for the four stay to fork-leg lugs. The brace-to-leg support at the top are 1/4 inch Cycle studs and nuts/washers . For all the road holder forks on featherbed Dominators up until about 1968. Will Horgan at Stainless Classics do sell them in stainless steel - make sure you get the reduced head hexagon and reduced diameter washer or they won't fit. Cheers, Howard
I have a 1959 99 in origin…
I have a 1959 99 in original condition (but still in pieces!) and I'm pretty sure that the top studs for the mudguard bridge are 1/4"- Whitworth into the leg and BCY for the nut. I also have a pair of 1955 fork legs with the studs in a different position but they are studs, not bolts/setscrews. I will try to check over the weekend. Cheers, Lionel
Previously Barry Robinson wrote:
Previously robert_tuck wrote:
Later bikes may have had UNC threads in ally and unf into nuts. Or a bastard mixture!.
In 1959 however it would have been Imperial and I'm trying to find out what thread it was they used then, someone must know surely? It won't be Unified.
Anyway thanks for your response.
Barry
Previously howard_robinson…
Previously howard_robinson wrote:
Hello again Barry - I already told you it's 5/16 inch BS Cycle (26TPI) for the four stay to fork-leg lugs. The brace-to-leg support at the top are 1/4 inch Cycle studs and nuts/washers . For all the road holder forks on featherbed Dominators up until about 1968. Will Horgan at Stainless Classics do sell them in stainless steel - make sure you get the reduced head hexagon and reduced diameter washer or they won't fit. Cheers, Howard
Hi Howard, are you actually saying the studs fitted by the factory into the fork leg which support the mudguard bridge are cycle? Lionel is saying they are BSW which seems me to be more sensible as cycle is too fine and bad practice. Now both of you say the bores are 1/4 which suggests mine have been bored out to 5/16 at a later date so in a sense I'm on my own in finding out what thread they now. I'm reluctant to go poking around in there with a variety of 5/16 taps but I have no choice now. Thanks for going into all this for me.Barry
PS reference your comment about the stays and the fork lugs by which I think you are talking about the 4 mudguard stays which attach to the ends of the mudguard and to the lugs in the bottom lower end of the legs, just to be clear I wasn't asking about those luckily they seem ok.
Hi Barry, Logic and normal…
Hi Barry, Logic and normal Norton practise in other areas would say these should be 1/4 whitworth into the ally. As they are small and vulnerable the studs often shear off flush so are drilled out and re-tapped 5/16 whit or unc on later bikes. If the guard is tight or loose correct this after checking the forks have been aligned on the wheel axle(pinch bolt loose ,nearside leg free to slide on axle).
Hello Barry. once you esta…
Hello Barry. once you establish what you have. if the threads in the legs are ok if not standard fittment i suppose you could have studs made to alter the threads to suit .
BARRY
Hi Barry, In my experience…
Hi Barry, In my experience only the late studs have the coarse UNC thread. In fact on my 1969 Commando they were UNC all the way up, nuts and all. On Dommies and long road-holders I am sure that they are 1/4 inch Cycle thread tho' of course they could be 1/4 BSF as both are 26 tpi. I did once try to use the forward rocker cover studs (that were 1/4 inch BSW with a 1/4 inch Cycle portion for the nut) instead, but no go. They were fine threads at both ends. Good Luck, Howard .
Thanks everyone for the in…
Thanks everyone for the info etc. I will let you know how I get on. Barry
Just to clarify - they def…
Just to clarify - they definitely wouldn't be Cycle thread into the alloy. These are Whitworth, but the external thread for the nut is either BSF or Cycle. (I haven't had a chance to check) They are very short and it would probably be expensive to get studs made with two different thread forms so it's either DiY or just go for Whitworth for the whole stud. Who cares or who sees the outer part of the thread with the nut & washers on?
Previously howard_robinson wrote:
Hi Barry, In my experience only the late studs have the coarse UNC thread. In fact on my 1969 Commando they were UNC all the way up, nuts and all. On Dommies and long road-holders I am sure that they are 1/4 inch Cycle thread tho' of course they could be 1/4 BSF as both are 26 tpi. I did once try to use the forward rocker cover studs (that were 1/4 inch BSW with a 1/4 inch Cycle portion for the nut) instead, but no go. They were fine threads at both ends. Good Luck, Howard .
Hi Lionel, thanks for conf…
Hi Lionel, thanks for confirming that the thread into the fork leg would be BSW originally. Although ,courtesy of a friend with lathe, I can get any studs I want made up, once I know what 5/16 thread I am dealing with I will go for bolts instead. Best wishes Barry.
My 1959 99 has 26 tpi cycl…
My 1959 99 has 26 tpi cycle thread studs for the mudguard bridge. Not an ideal engineering solution but I am sure Norton Motors knew what they were doing. Cutting costs probably.
Ok, here's a bit of fun,…
Ok, here's a bit of fun, the votes so far;
in favour of cycle............4
in favour of BSW/BSF......3
Barry
Who do we trust to hold th…
Who do we trust to hold the bet pot??.
Actually, shuffle shuffle…
Actually, shuffle shuffle looking slightly embarrassed, I am right.
Part number 06-7523 for Dominators 1/4" x 26 x 1" CEI
Part number 06-0356 for Commandos 1/4" x 20 x 1" UNC
So there.
Gordon.
Hi Gordon, Don't be embar…
Hi Gordon,
Don't be embarrassed, original source material, when available, is always the most reliable evidence. Right is right.
Although now something of bystander on this particular question, I note that your information shows that when AMC? changed to a coarser thread on the Commando it was correcting Norton's bad engineering practice in using cycle.
I'm not knocking Norton but I've just read Bill Cakebreads book (p93-94) on his time at Plumstead where he relates that AMC discovered that the steering heads on the Featherbed frame were 2deg out resulting in warranty claims for bent mudguards impacting on the frame.
All part of the rich tapestry of our British bike history.
And don't get me wrong I love my first Norton just a much as my two AMC bikes, I am proud to own a machine with such a fine pedigree. When I told my old Dad (now 94) that I had bought a Norton he related how when he was young he drooled over Nortons and Velocettes but could never afford one.
Anyway back to the garage, this afternoon I am putting the engine and gearbox back into the newly painted frame at last, I need to crack on, we're booked into the West Kent Run this year!
Barry
You are on the right track!!. Not likely to be cycle into the ally but will be cycle for the nut.