gearbox top bolt

F

fizzer

Joined

Dec 2, 2013

Messages

1

• Dec 2, 2013

• #1

hi, this is my first post so please be gentle!
i am in the process of individualising my 73`commando, i would like to know the size and type of thread of the gearbox top bolt? i have an alloy cradle and the original bolt is only half way through the nut.
i have so far rebuilt the engine and gearbox rebuilt the wheels, frame coated, still feels like a way to go but i dont want to rush it at the last hour.
fizzer.

 

FastFred

Joined

Dec 23, 2009

Messages

593

• Dec 2, 2013

• #2

Could be 5/8 UNF, check out NORVIL website or Andover RGM and they may state what threadis used.

 

DogT

VIP MEMBER

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Jan 20, 2009

Messages

7,394

• Dec 2, 2013

• #3

Gearbox top nut 06.0420 9/16 x 20 CEI. Bolt is special. Bolt is 14367.

 

L.A.B.

Moderator

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Nov 20, 2004

Messages

20,416

• Dec 2, 2013

• #4

DogT said:

Gearbox top nut 06.0420 9/16 x 20 CEI. Bolt is special. Bolt is 14367.

Click to expand...

'72 - '74 models have a different 18 tpi (UNF) gearbox top mount nut and bolt.

http://www.oldbritts.com/1972_g5.html
http://www.oldbritts.com/nor_comm_72_5.html

 

T

toppy

Joined

Dec 2, 2012

Messages

896

• Dec 2, 2013

• #5

I just checked mine as the whole thing is in bits (again) an as LAB says its 9/16unf

 

DogT

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• Dec 2, 2013

• #6

I stand corrected, again.

 

P

pete.v

Joined

Oct 31, 2009

Messages

5,193

• Dec 2, 2013

• #7

fizzer said:

hi, this is my first post so please be gentle!
i am in the process of individualising my 73`commando, i would like to know the size and type of thread of the gearbox top bolt? i have an alloy cradle and the original bolt is only half way through the nut.
i have so far rebuilt the engine and gearbox rebuilt the wheels, frame coated, still feels like a way to go but i dont want to rush it at the last hour.
fizzer.

Click to expand...

You can get a 5 1/2" at the bolt/fastener stores. I just got a 5 1/2" because i added an outrigger and needed the extra length. Cost me $2. I is a grade 5 bolt. Grade 8 is overkill for this application.

 

B

B.Rad

Joined

Feb 28, 2012

Messages

287

• Dec 2, 2013

• #8

Yes. Grade 5 is fine.
Bradley

 

T

toppy

Joined

Dec 2, 2012

Messages

896

• Dec 3, 2013

• #9

Early Commando an featherbeds had a different thread to mk2 which had UNF for the american market then the mk3 had a 5/8 bolt. So we may all have the right answer depending on which year or what a previous owner may have fitted back in the day.

 

O

olChris

Joined

Oct 6, 2013

Messages

865

• Dec 3, 2013

• #10

:lol: :lol: :lol: :lol: .. Nortons!! How can a bolt be so compex :shock: :shock: :shock: .. Over kill for a bolt @ $2, i think i would overkill for another $2 = $4.00 .. There is only another $4k to go. (she will never know)!!

 

ZFD

Joined

Jan 23, 2010

Messages

673

• Dec 3, 2013

• #11

NM14637 with the corresponding nut 06-0420 was the far more elegant solution and we have just had a batch re-manufactured. 9/16"x20TPI it is. The drawing is dated 09.07.1952, so all Dommis had them, too.

 

R

Rohan

Joined

Aug 26, 2010

Messages

8,215

• Dec 4, 2013

• #12

Dommies even earlier than 1952 featherbeds used 20 tpi threads on the gearbox top bolt too. ?
But 26 tpi on the bottom bolt...

20 TPI (threads per inch) being in this case the coarse thread version of British Cycyle Thread, in case anyone was wondering.
(and 26 tpi being the Fine Thread version of British Cycle Thread, as many earlier Nortons used, almost exclusively).

BTW, 9/16" 20 tpi is near identical to 14mm spark plug thread - not that that helps anything.
But you can test you have the correct nut by threading a 14mm spark plug into it...