Crankshaft stud material

Be aware that 10.9 grade bolts are tough cookies but can be machined with sharp tools.

Can someone clarify crankshaft assembly? I understand from reading Bacon's Norton Twins Restoration that 2 out of 6 studs were supposed to be close fit to supplement the dowel, but the remaining 4 have clearance holes.  I.e. not snug fit.  Is this true?  And might it explain Martin's apparent problem?

And did bolt material change between the first 500cc Dommies and the final Commando with twice the power?  Wouldn't grade 10.9 or equivalent have been unusual in the late 1940's?  Or is the information "commercially confidential"?

I would not be happy to machine crankshaft bolt threads unless I was advised to do so by an expert in this field due to my understanding of rolled threads are less prone to stresses  induced during the machining process using threading on a lathe or taps and die methods.

Chapter 3 in the DSNs is full of useful information regarding Dominator crankshafts. Page 20 has some data relevant to this thread about the crankshaft stud / bolts and finish clearances.  My understanding being that the finish of crankshaft holes was changed when the 600cc engines entered production.

That still leaves material grade.  It must have been on design rawings somewhere.   Are such drawings accessible anywhere?  Or even the material notes?

Cut threads would be fine. The reason for rolled threads being used on certain applications is the grain flow is uninterrupted.

As for a suitable stud material, I would use EN16T which is a readily available medium carbon steel. You could use EN24 but it would be overkill.