Base studs

Hi guys, another quick question on the rebuild.

I need some new cylinder base nuts to make it look pretty but having checked the threads it seems I have the cycle thread ones. My local shop doesn't have them, they just have the UNF kind.

My question is: Can I fit the later studs so I can use UNF nuts or is the thread into the crankcases different too?

Thanks
John

pommie john said:

Can I fit the later studs so I can use UNF nuts or is the thread into the crankcases different too?

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The crankcase threads would be 55 degree Whitworth profile, whereas the later threads are 60 degree UNC so maybe run a UNC tap down the threads before fitting UNF/UNC studs (but check they are not helicoiled first).

The threads into the crankcase on the earlier ones are Whitworth, which is close enough to the Commando UNC ones that there should be no problems.

Take one out of your crankcases to take along with you, along with a whitworth nut to suit, so you can check though. No telling what may happened along the way....

Don't forget that you will now need two different wrench sets for any engine work.
Which is absolutely guaranteed to catch someone out along the way...

Thanks for the replies.

maybe I should hunt down some cycle thread nuts to simplify it.

One other thing, where can I check the year of my motor. The engine number is 20-109274

Thanks

pommie john said:

One other thing, where can I check the year of my motor. The engine number is 20-109274

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That's a 1964 Atlas.

The thread degree angle don't matter as the spiral is the same, though the 55' is the stronger thread. I'd call vendors for the fasteners in Cad or SS nuts. If annal can even put in Timserts in Whitworht thread form and size.

L.A.B. said:

pommie john said:

One other thing, where can I check the year of my motor. The engine number is 20-109274

Click to expand...

That's a 1964 Atlas.

Click to expand...

Holy heck! I've been calling it a Commando for 20 years!

It sits like a Commando engine, inclined in the frame. No wonder it's got cycle thread base nuts .

Yeah as much a rubber mounted Commando as my P!! even with the canted forward engine to fool strangers. Both might out leap most C'do though.

I think they used BSW/BSC studs and BSC nuts through some time in 71 or 72. I got my BSC SS nuts from RGM, very nice with the thick beveled washers too, he may have the studs too, don't know, Roger knows if you care to ask. He's got the UNF too. I just put a dab of silver paint on top of the steel studs where you see them after I cleaned them up.

Dave
69S

Swapped the studs in mine when I was a 12 yr old .
Just used two nuts to lock , and a good fitting spanner,

Dont hurry , they wind in & out , or out & in , clean .IF
you are carefull to see you keep them square to the face
and dont hook it over sos its cross threaded. JUST LIKE
ANY OTHER nut'n'bolt.

Used the angled spanner, stud between fingers for first
2 1/2 continuos turns , one at a time .

Dont try and screw them through the bottom of the crankcase.
If youve got delicate sensitivities you can feel when there home
as they go down dead even resistance, till the last IOTA ,
where you stop immediately . :|