Thread specification - Atlas rear wheel lugs/nuts (2014)

[texasSlick]

I need to buy a tap to clean up the threads in the three long rear wheel to brake drum lugs or nuts.
I measure the studs at 7/16 inch - what is thread pitch and specification, I.e. BS or W?

I suppose early bolt up Cdo is the same. Anyone know?

Slick

 

[dynodave]

TS

featherbed is 26TPI CEI same with the rear hub bearing retainer/speedo coupler and front wheel bearing retainer, axles are 20tpi probably the 20 series of CEI (coarse)



commando is 20TPI UNF same with the rear hub bearing retainer/speedo coupler and front wheel bearing retainer, axles are 18tpi

 

[texasSlick]

Thanks Dave!

Slick

 

[norton bob]

I think the threads changed from cycle sometime after the move to AMC in 1963 our 67 Atlas is different to the early 60's bikes and is probably UNF.

 

[dynodave]

"our 67 Atlas is different to the early 60's bikes and is probably UNF."
Not sure- did you even check?

63-65 parts book: sleeve nut pn 18233
66-68 parts book: sleeve nut pn 18233
my 63, (2) 66 and 68 atlas, one of the very last made, all of them CEI

69-70 commando parts book sleeve nut 06-0323 UN threads according to history and AN

 

[norton bob]

I have bikes from 60 and 67 and the parts are NOT interchangeable .the early ones are cycle ,never checked what the later ones are.Lots of threaded items were changed at AMC.Perhaps they should have all been cycle as per the parts lists. I don't think they were that fussed just did what they had to do to finish bikes.Also after 50 years you could find all manner of substitutions have been made.Perhaps I should just say don't be surprised if your new nuts dont fit your studs as some of the suppliers dont think it matters.

 

[Bernhard]

1963 Atlas might have been made in Birmingham before they moved to Plumstead - when all bets are off what type of threads you have where. The easiest way is to check with a thread gauge could be 26 tpi cycle thread, BSF or BSW.

 

[oldmikew]

I need to buy a tap to clean up the threads in the three long rear wheel to brake drum lugs or nuts.
I measure the studs at 7/16 inch - what is thread pitch and specification, I.e. BS or W?

I suppose early bolt up Cdo is the same. Anyone know?

Slick

I was In Russels of Falcon road London when this bloke came in wanting early commando stuff... A catalogue was produced with the comment that a lot of the part nembers were the same as late AMC

They, in fact may still have original Atlas stuff . Worth an Email

 

[norton bob]

Russels are well worth contacting, but only have one staff man who will deal with old brit stuff, He is not always there.

 

[mdt-son]

I have bikes from 60 and 67 and the parts are NOT interchangeable .the early ones are cycle ,never checked what the later ones are.Lots of threaded items were changed at AMC.Perhaps they should have all been cycle as per the parts lists. I don't think they were that fussed just did what they had to do to finish bikes.Also after 50 years you could find all manner of substitutions have been made.Perhaps I should just say don't be surprised if your new nuts dont fit your studs as some of the suppliers dont think it matters.

AMC relied heavily on BSC/CEI threads and I would be surprised to learn that other thread types were used with the old Norton factory in Birmingham. in fact, the entire british bike industry relied on BSC/CEI (that's why it's calles "British Standard Cycle"). AMC had an extensive tooling shop and produces almost every bolt, stud and nut themselves, Nyloc nuts exempted. Some of the bolts made are a work of art!
This continued right up to the factory closure in July 1969.
For the Commando, many secondary fasteners were supplied by outside suppliers, I guess the result of a change in policy to cut costs (who wants to pay for bolts with a rounded hex head?) and maybe because tooling for BSC/CEI was becoming expensive. Hence the swap from BSC/CEI to UNF. Was it a progress? Sure, it made sourcing suppliers easier, but caused a headache to owners.

After almost 60 years, it's hard to tell what previous owners did to the bike, and you can only make a statement based on factory spec or a NOS part.

-Knut

 

[L.A.B.]

AMC relied heavily on BSC/CEI threads and I would be surprised to learn that other thread types were used with the old Norton factory in Birmingham. in fact, the entire british bike industry relied on BSC/CEI (that's why it's calles "British Standard Cycle").

Various sections of British industry simply adopted the thread standard(s) that suited their particular trade. The motorcycle evolved from the bicycle and many motorcycle manufacturers started out either making bicycles or bicycle components so it's logical that the use of Cycle thread continued into motorcycle production. Engines, gearboxes etc. had BSW and BSF threads which were certainy used at the old Norton factory and beyond into Commando production. BSF and BSW being the thread standard used throughout British manufacturing.
Likewise, assemblies containing fasteners smaller than 1/4" diameter typically used the BA thread system (carbs, electrical parts). Pipe fittings once again had their own thread standard (BSP).

For the Commando, many secondary fasteners were supplied by outside suppliers, I guess the result of a change in policy to cut costs (who wants to pay for bolts with a rounded hex head?) and maybe because tooling for BSC/CEI was becoming expensive. Hence the swap from BSC/CEI to BSF, BSW and UNF. Was it a progress?

BSF and BSW had been in use for years. The "swap" (made rather slowly in the case of Norton but faster by BSA and Triumph) was to Unified (UNF, UNEF, UNC etc.) thread in the late '60s (although UK car and other vehicle manufacturers adopted the Unified system several years earlier).
The Commando had many Unified threads from the beginning and a few more were added later, however, the change to all Unified was never completed and by which time the world including the UK was beginning to change over to metric fasteners.

 

[mdt-son]

Engines, gearboxes etc. had BSW and BSF threads which were certainy used at the old Norton factory and beyond into Commando production. BSF and BSW being the thread standard used throughout British manufacturing.

Agreed. I should have been less rigorous in my statement above. Of course other threads were in use at Norton and AMC, but rarely for parts designed and manufactured in-house. Was there ever use of BSF or BSW in Norton engines and gearboxes? These are very coarse threads, typically half the pitch of corresponding CEI threads, and probably unsuitable for use in motorcycles.

The 5 bolts and one stud clamping the crankshaft of the Norton still had CEI threads by 1971 (3/8x26 CEI), later changed to 3/8x24 UNF. Not much of a pitch difference, and both threads have 60 degree flanks. The change was probably prompted by tooling considerations. The studs holding the barrel footing also had CEI threads by 1971, they too were changed to UNC/UNF for 1972. However, the extra fine threads for the worm nut and the camshaft nut are UNEF (Unified extra fine - the latter 3/4x20 TPI) probably from the outset (?), simply because CEI threads are not defined for this size and pitch. On the drive side, the rotor axle nut was 5/8x20 CEI until the end of the Commando line ....

-Knut

 

[L.A.B.]

Was there ever use of BSF or BSW in Norton engines and gearboxes?

To name a few that readily spring to mind;

Head steady to head allen screws (BSF)
Carb manifold to head screws (BSW)
Inlet rocker cover stud inner end (BSF)
Exhaust rocker cover stud inner (BSW)
Rocker feed banjos (BSF)
Rocker cover plate bolts (BSW)
Cylinder base studs pre-200000 inner end (BSW)
Head to barrel 5/16 studs head end (BSF)
Early Timing cover screws (BSW)
Camshaft AAU bolt (BSF)
Camshaft chain tensioner stud inner (BSW)
Oil pump stud inner (BSW)

Gearbox inner cover stud inner end (BSF)
Gearbox drain plug (3/8 BSF)
Gearshift stop plate bolts (BSF)

These are very coarse threads, typically half the pitch of corresponding CEI threads, and probably unsuitable for use in motorcycles.

Coarse threads are exactly what's needed into alloy therefore hardly unsuitable in my (or their) opinion.

The studs holding the barrel footing also had CEI threads by 1971,

I think you will find BSW x BSCycle base studs go back to Bracebridge St. times.

they too were changed to UNC for 1972.

UNC x UNF.

 

[triumph2]

The 5 bolts and one stud clamping the crankshaft of the Norton still had CEI threads by 1971 (3/8x26 CEI), later changed to 3/8x24 UNF. Not much of a pitch difference, and both threads have 60 degree flanks. The change was probably prompted by tooling considerations.
-Knut

Small point but I believe the studs were 5/16 up to the MK3 which went to 3/8" dia.

 

[mdt-son]

Coarse threads are exactly what's needed into alloy therefore hardly unsuitable in my (or their) opinion.

Les, thank you for your effort pointing this out. Very useful! I had no idea there were all these instances of BSF and BSW. Ouch!
However, I knew that studs secured in alloy needs coarse threads but there was also a coarse CEI thread ..... I should have done my homework properly.
Yes, I believe too the BSF/CEI studs go back to Bracebridge St. times.

To round off this information exchange, it would be useful to know which BSW/BSW threads were retained after 1972!

Small point but I believe the studs were 5/16 up to the MK3 which went to 3/8" dia.

You are absolutely right. I stand corrected. The corrected statement is:

The 5 bolts and one stud clamping the crankshaft of the Norton still had CEI threads by 1971 (5/16x26 CEI), changed for 1973 to 5/16x24 UNF and again changed for 1975 to 3/8x24 UNF (different bolt pattern & number of bolts).

-Knut

 

[L.A.B.]

I knew that studs secured in alloy needs coarse threads but there was also a coarse CEI thread

Well, there was 20 tpi Cycle thread if that's what you mean but that tended to be in the larger diameters rather than bolts or studs, however, don't automatically assume a large diameter 20 tpi thread is necessarily Cycle on a Commando.

 

[mdt-son]

I was wrong again. There is no continuous table of 20 tpi BSC thread sizes apparently. 7/16" and 1/2" sizes did come in 20tpi options. Makes one wonder why the british motorbike industry didn't switch to the Unified Threads Standard (UTS) in the early 60's, especially since a large percentage of the output was exported to USA.

An extract from www.boltscience.com:
"In November 1948 the Unified thread was agreed upon by the UK, the US and Canada to be used as the single standard for all countries using inch units. In 1965 the British Standards Institution issued a policy statement requesting that organisations should regard the BSW, BSF and BA threads as obsolescent. The first choice replacement for future designs was to be the ISO metric thread with the ISO inch (Unified) thread being the second choice."

-Knut

 

[norton bob]

Just ordered a set of 5/16 BSF socket head cap bolts for the 67 Atlas, Think use of these go back to the fifties. The rear drum is probably a Commando item.