Chaincase fixing screws thread

[pierodn]

Please, what is the thread of the three CHAINCASE FIXING SCREWS part-no: 06.0375.
Thank you.
Piero

 

[L.A.B.]

https://andover-norton.co.uk/en/shop-details/15244

"06.0375
CHAINCASE FIXING SCREW 1/4" WHIT ZINC PLATED"

 

[baz]

Please don't forget to replace the tab washers
The first commando I bought had one of those bolts fall out
It wrecked the chain case/alternator and bent the gearbox main shaft
There was no sign of any tab washers in the case

 

[lazyeye6]

and seal the threads of those fixing screws or oil will migrate into the chain case.

 

[Craig]

Yup , I made mistake of using the 3 tab washers so many times , eventually one failed in 2 pieces , cost me new complete alternator, new inner chain case and almost an unbearable smell making repairs , thankfully no other damage and thank my lucky stars , I was able ride the smelly, smoking beast home into my shed before stopping (5km) , tried welding posts back onto chain case but couldn’t get them oriented properly ..... harshest lesson learned from this bike ....

 

[acadian]

Or fit studs and use lock nuts

 

[pierodn]

Sorry but i need to know the thread because i have the case with the holes welded and closed so that i need to rethread
I know that the nuts are of 1/4 but i dont know the tpi, i must buy the die and tap.
Thanks
Piero

 

[L.A.B.]

Sorry but i need to know the thread because i have the case with the holes welded and closed so that i need to rethread
I know that the nuts are of 1/4 but i dont know the tpi, i must buy the die and tap.

1/4 Whitworth is 20 tpi.
https://britishfasteners.com/threads/bsw.html

 

[L.A.B.]

1/4 UNC (60-degree thread angle) on later models but still 20 tpi:
https://britishfasteners.com/threads/unc.html

06.2669
https://andover-norton.co.uk/en/shop-details/15934/chaincase-fixing-screw-1-4-unc-zinc-plated

 

[Onder]

There is so little thread in those holes. Using the tab washer loses some of them. I don't use the tab washers simply loctite the bolts in and Ive never had one come loose. Studs with red loctite might not be a bad idea.

 

[DogT]

I replaced those bolts with UNF/UNC studs and nuts, ala hobot. To the purist, the WW thread is a different taper, but the UNC fit fine for me. And I found them at the local auto store for a few cents, UNF on one side and UNC on the other. But you do have to use thinner lock nuts or grind the nuts down to clear the chain. But it sure makes fitting the outer chain case lots easier. Locktite, for sure. One of mine had already been tapped out to 3/8", undoubtedly striped. "It wasn't me."