Rear hub thread size for 1972 Commando?

[Cuppy]

Does anyone know the rear hub thread size and pitch? I purchased a used hub (listed from a '74 Commando) and speedo lockring in order to have a new 18" wheel laced. I can't get the lockring to thread in more than 1/2 turn and I don't want to damage the threads. Do not see any apparent thread damage on hub or LR. My thread gauge (Craftsman US) indicates 20 tpi on both. The lockring is from a trusted British bike US supplier not AN.

 

[Shelby-Right]

Does anyone know the rear hub thread size and pitch? I purchased a used hub (listed from a '74 Commando) and speedo lockring in order to have a new 18" wheel laced. I can't get the lockring to thread in more than 1/2 turn and I don't want to damage the threads. Do not see any apparent thread damage on hub or LR. My thread gauge (Craftsman US) indicates 20 tpi on both. The lockring is from a trusted British bike US supplier no AN.

Can you put it in a lathe and get a fine file , then at slowish rotation file little off the top of the threads then go from the start of the thread at 45 degrees on each side to basically round them off , then give it a good wire brush , then put a little anti sieze or grease on it and give it a try . .cheers

 

[L.A.B.]

Does anyone know the rear hub thread size and pitch?

My thread gauge (Craftsman US) indicates 20 tpi on both.

I'd take a guess that it's Unified so likely to be 20-UN.
All '68-'74 Commando hubs should have the same thread as the lockring is the same part (060317).

 

[Cuppy]

Can you put it in a lathe and get a fine file , then at slowish rotation file little off the top of the threads then go from the start of the thread at 45 degrees on each side to basically round them off , then give it a good wire brush , then put a little anti sieze or grease on it and give it a try . .cheers

I don't have a lathe or I could try. Trying to find a local machine shop.

 

[Shelby-Right]

Battery drill , a round bit of wood , a bolt and nut jam it on . Etc

 

[Cuppy]

It's strange because if I google the part number 06-0317, I get references to both 20 and 26 tpi.

 

[L.A.B.]

It's strange because if I google the part number 06-0317, I get references to both 20 and 26 tpi.

26 TPI is pre Commando.

REAR WHEEL LOCKRING FINE THREAD - PRE COMMANDO

18232 RGM NORTON 067702

www.rgmnorton.co.uk

Commando 06-0317 is 20 TPI

REAR WHEEL LOCKRING, COMMANDO, COARSE

RGM NORTON 060317

www.rgmnorton.co.uk

 

[Cuppy]

I'd take a guess that it's Unified so likely to be 20-UN.
All '68-'74 Commando hubs should have the same thread as the lockring is the same part (060317).

Lab,

I asked AN about the thread and they said it was 20 tpi cycle. I have since found that the lockring I purchased was sourced from AN. Is it possible the hub I have is 20 tpi UN and the lockring is 20 tpi Cycle? I am seeing 20 tpi on each with a thread gauge but can't judge pitch. Threads appear in good condition but won't thread on. Unfortunately there's not an old fashion machine shop around anymore.

 

[L.A.B.]

I can't see how it could be 20 TPI Cycle thread as 20 TPI Cycle was supposedly phased out when CEI became BSC in 1938 and was supposed to have been replaced by 20 TPI Whit Form.






Also in this video Ashley says the Commando front drum (lockring?) is "UNF" (can't be UNF as there's no such UNF size but 20-UN) so I can't see how the rear lockring can be 20 TPI Cycle thread so something isn't right?


Only 7/16" and 1/2" UNF are 20 TPI.
Why would Norton change from 26 Cycle to 20 Cycle (if that's what it is) when other threads were changing to Unified as that makes no sense to me.

 

[Cuppy]

I can't see how it could be 20 TPI Cycle thread as 20 TPI Cycle was supposedly phased out when CEI became BSC in 1938 and was supposed to have been replaced by 20 TPI Whit Form.




Also in this video Ashley says the Commando front drum (lockring?) is "UNF" (can't be UNF as there's no such size but 20-UN) so I can't see how the rear lockring can be 20 TPI Cycle thread so something isn't right?

OK.
Your right, something doesn't add up. Have to find a machinist or source another hub.

 

[Cuppy]

AN replied back and confirmed the lockring as being UNF. Geez

Technical​

to me, Technical

[td]

3:03 AM (2 hours ago)​

[/td]​

06.0317 is 20tpi UNF

 

[L.A.B.]

AN replied back and confirmed the lockring as being UNF. Geez

Ok, although it can't be UNF or even UNEF but Unified (UN-20) do they really not know the difference?

 

[kommando]

You can chase the thread in the hub, get a second speedo lockring and grind three partial slots 120 degrees apart in the threaded section, Then use that to cut the hub thread to match the lockring thread angle. Be very diligent on the first few turns to make sure you follow the existing thread and not create one at an angle or start a second.

Here is an exhaust ring for a T120 at 30 thou oversize, to get it to fit a worn head and deepen the existing threads, I ground four slots for this one.

Then used it to cut the old worn threads deeper, then used an uncut one for final assembly.

 

[johnm]

You can chase the thread in the hub, get a second speedo lockring and grind three partial slots 120 degrees apart in the threaded section, Then use that to cut the hub thread to match the lockring thread angle. Be very diligent on the first few turns to make sure you follow the existing thread and not create one at an angle or start a second.

Here is an exhaust ring for a T120 at 30 thou oversize, to get it to fit a worn head and deepen the existing threads, I ground four slots for this one.

Then used it to cut the old worn threads deeper, then used an uncut one for final assembly.

Plus add some valve grinding paste and work it back and forth.

 

[Cuppy]

You can chase the thread in the hub, get a second speedo lockring and grind three partial slots 120 degrees apart in the threaded section, Then use that to cut the hub thread to match the lockring thread angle. Be very diligent on the first few turns to make sure you follow the existing thread and not create one at an angle or start a second.

Here is an exhaust ring for a T120 at 30 thou oversize, to get it to fit a worn head and deepen the existing threads, I ground four slots for this one.

Then used it to cut the old worn threads deeper, then used an uncut one for final assembly.

OK. I might give that a try.

 

[L.A.B.]

Have you tried heating the hub thread?

 

[Shelby-Right]

Have you tried heating the hub thread?

If it's too tight in the thread , adding heat will just help it bind up and seize , I think it's better to add more clearance to the replaceable part , that way the hub thread is un damaged . And you can always get another, locking ring .

 

[johnm]

If it's too tight in the thread , adding heat will just help it bind up and seize , I think it's better to add more clearance to the replaceable part , that way the hub thread is un damaged . And you can always get another, locking ring .

Hub thread will be bigger with heat.

 

[bmepkid]

I'll see if I can get that thread count tonight. I have a bare rear hub that I can check. By the way, it's going up for sale.

 

[Cuppy]

Have you tried heating the hub thread?

No I have not.