Thread of Atlas / Early Commando steering stem

[laurentdom]

Hi All,

I have a problem with installing the lower 7" 3/8 yoke on my Featherbed frame.

The so-called "fork head race adjuster nut" (the one which is located just under the top yoke) that I used on my 7" yoke is very difficult to screw on the 7" 3/8 stem despite the diameter and the thread being the same on both types of yokes.

I think that the thread on the 7" 3/8 stem needs to be re-cut a little bit. Before ordering the wrong die, I would like to verify the thread / type of thread (BSF ???) and diameter of the steering stem.

Thks for your help!

 

[Rohan]

Without getting out the thread gauges, there is almost no BSF on Nortons anywhere - note thats an almost, not a never. (BSF is quite a coarse thread).
Nortons were a Cycle Thread user, then switched to UNF for the Commando. But it wasn't a wholehearted switch !
But YOU probably need to get out the thread gauges, and confirm that old and new threads are indeed identical.
its likely to be something oddball like 32 tpi Cycle Thread, from memory (which I never trust, always measure to confirm).

A dienut is likely to be ferociously expensive, maybe the NOC could advise someone who has one and can loan or hire it out ?
It may be simpler to have the threads lightly skimmed in a lathe. ? Probably not on Xmas day though...
Or even filed with a thread file, there is likely to be a tight or sticky burred area of thread
Hopethishelps, Goodluck.

 

[gjr]

You don't say what the longer stem is off, but my parts book shows pn 15630 for the Atlas and 06.0341 for the Fastback. Andover Norton shows the nuts as two different parts. See http://www.nortonmotors.de/ANIL/SI%20Forks.htm Item no. 30.

Greg

 

[laurentdom]

Thanks a lot Greg and Rohan,

I'm about to follow your way Rohan: I ordered a thread file and will try and "reshape" the part of the stem which seems faulty. By the way, I learned from the NOC web site that it's a 26 tpi thread.

Merry Christmas to you and your families.

 

[marinatlas]

Hi Laurent, take care as there were two different thread for those stem (and then for the two nuts , call them like that !!), the one for the domie and the one for the early commando, though they look very similar...........

 

[marinatlas]

It was 26 TPI for one and 28 TPI for the other............

 

[Chris]

Hi Laurentdom

Where abouts are you?

Marinatlas is correct about the threads. I asked this question a little while ago & he replied. I got a dia from Tracey Tools for under 20 quid delivered.
If you are in the Uk I will loan it out if you cover postage.

all the best Chris

 

[gjr]

You won't need thread gauges to check if the pitch is the same. Take the two stems and interlock the threads. If the threads remain meshed for the entire length, the pitch is the same. If they go out of register, they are not.

Greg

 

[Rohan]

And if they are not the same, the thread gauge will help sort out which is 26 tpi (Cycle Thread) and which is 28 tpi (UNF = american thread).
Never the twain will mix....

 

[laurentdom]

Thanks to you all!

I got the confirmation that the threads are different as you highlight it Pierre-François: 26 tpi on a 7" Dominator yoke stem and 28 tpi on a 7" 3/8 (late Atlas / early Commando) one.

As they said in the RAF workshops during WW II: "Don't assume, check!" in particular when there is no reason for changing from 26 to 28.

"When it's obvious, be suspicious".

Cheers


L.

 

[B.Rad]

hello All
just a small correction first. BSF is NOT a coarse thread. british standard fine thread. In the english system, whitworth was the equivalent of UNC, BSF equivalent of UNF.

repairing the thread. a thread file does not have sharp cutting edges so tends to rub metal away rather then cut. they are not good for removing gross deformities

In the case of severe metal deformation of the thread, a good sharp small triangular file will remove visible gross deformities quickly. then, if any tight spots remain, the application of fine valve grinding paste can be liberally applied to nut and stem. then using regular reversals, work the nut down the stem. if there are only minor imperfections this does not take very long and you dont fork out for an expensive tool that may not see much use. if progress is a bit slow, use a coarser grinding paste.

of course thorough cleaning after is necessary.

this works, and the result is still a very usable thread.
hope this helps Bradley

 

[Rohan]

hello All
just a small correction first. BSF is NOT a coarse thread. british standard fine thread. /quote]

Compared to British Cycle Thread, (26 tpi, mostly) which Nortons used almost exclusively until the Commando, then bsf - IS - a coarser thread !
You only have to look at thread counts, in any given bolt size, to see this.
Perhaps Bradley can quote the exception that proves this rule.

And BSF was rarely used, ANYWHERE, on Nortons, which was the whole point of the comment.
You often see BSF bandied about in mention of Nortons, and this just isn't so....

 

[gjr]

I got the confirmation that the threads are different as you highlight it Pierre-François: 26 tpi on a 7" Dominator yoke stem and 28 tpi on a 7" 3/8 (late Atlas / early Commando) one.
.

I was caught out by the 26 TPI note on the A/N parts list. Did Norton go back to 26 TPI for the '71 and later bikes or is that a typo ?

Greg

 

[Rohan]

The nut on the 850 disk-brake yokes is stamped with the 3 overlapping circles, to show its the UNF version.

Can you get a thread pitch gauge, and verify the tpi on your yoke(s)....

 

[B.Rad]

hello All
just a small correction first. BSF is NOT a coarse thread. british standard fine thread. /quote]

Compared to British Cycle Thread, (26 tpi, mostly) which Nortons used almost exclusively until the Commando, then bsf - IS - a coarser thread !
You only have to look at thread counts, in any given bolt size, to see this.
Perhaps Bradley can quote the exception that proves this rule.

And BSF was rarely used, ANYWHERE, on Nortons, which was the whole point of the comment.
You often see BSF bandied about in mention of Nortons, and this just isn't so....

Rohan, giddayand hope ur well.
I will stand by this, BSF is NOT a coarse thread series, look at the name man,,BRITISH STANDARD FINE.
I am not getting into a pissing contest . I will not engage in stupid minor arguments over bullshit issues. this is what stuffs this forum up.
sometimes egos get in the way .
so, BSF is not, was not and never will be a known as a coarse thread series . To promote it as such is wrong .
Rohan, u may notice that I often sign off posts by inviting corrections to errors. this is so I may learn from others

""Perhaps Bradley can quote the exception that proves this rule."" AGAIN, there is no rule. I suppose if you are really looking for an argument , you will easily find one.
lets end this by recognising that the forum should be a place for co-operation. when someone has a counter opinion, respond in a co-operative , polite way.
Rohan, your spirit of co-operation was very evident when helping me with info for that old triumph. your information was very helpful indeed. so I thank you for that. all the best Bradley

 

[gjr]

To Whom it May Concern at Andover Norton,

Please put the thread specs back on your Service information page. It is invaluable when sorting out similar parts from 40-50 year old machines that may have been stored in boxes at some point in their lives.

The stem thread on a late Atlas lower triple clamp with 7 3/8" stanchion centers measures 26 tpi. An early Commando lower yoke measured 28 tpi.

Greg

 

[Rohan]

This info probably needs to be supplied directly to Andover Norton, rather than rely on chance that they read it here. ?
They can't correct stuff if they don't know its not right.

 

[Rohan]

Appy New Years to All !

Bradley, I stand by what I SAID - BSF is a coarser thread than Cycle Thread. (26 tpi, mostly)
And the exception is in Norton heads, where Nortons did do a few of the fittings into the alloy in BSF.
They must have found they had a BSF tap in the toolbox.. ??

BTW, the fine threads in that Triumph are all 30 tpi !!? - BSF wasn't fine enough for them either ?!?

 

[B.Rad]

Without getting out the thread gauges, there is almost no BSF on Nortons anywhere - note thats an almost, not a never. (BSF is quite a coarse thread).Nortons were a Cycle Thread user, then switched to UNF for the Commando. But it wasn't a wholehearted switch !
But YOU probably need to get out the thread gauges, and confirm that old and new threads are indeed identical.
its likely to be something oddball like 32 tpi Cycle Thread, from memory (which I never trust, always measure to confirm).

A dienut is likely to be ferociously expensive, maybe the NOC could advise someone who has one and can loan or hire it out ?
It may be simpler to have the threads lightly skimmed in a lathe. ? Probably not on Xmas day though...
Or even filed with a thread file, there is likely to be a tight or sticky burred area of thread
Hopethishelps, Goodluck.

mate, you seem to be a bit aggro over nothing, I only pointed out a fact . if you must have the last word, thats fine. enough shit fighting here already.
hope to continue to get your advice regarding the old Triumph.
happy new year and besty wishes bradley

 

[Rohan]

I''m not agrro over anything - I just merely mentioned it, and you wrote lots of words.
BSF may be finer than whitworth threads, but not much else.
And your fonts seem to be getting bigger....

I have mentioned to a few ebay sellers of BSF hardware that there is no BSF of that type anywhere on a Norton though.
Doesn't stop em advertising it though.
Don't know why they can't be had up for false advertising ??