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Roger mentioned this, and I did an article in the last edition of Yowl on the physics of the oil pressure/flow and how the groove geometry affects it.
Scott cranks are case hardened, but I do not know the steel grade(s) used. Silk were EN24 so you can post machine Silk cranks, but not Scott ones.
For the comment in the previous post about a crescent moon type thing, you can simpl use a round section (wire) circlip, but from my article as long as you have enough oil heading into the groove it won’t make any difference.
Scott cranks are fragile enough, I’d never recommend anyone machining through the case hardening especially near the crankpin as you are just inviting disaster by introducing machining stresses and/or grinding/machining paths which all just promote cracking. I’d also point out that TT Rep and some other cranks have no oil groove and from my running provided good quality rings are used, with high grade rollers and correct clearances/tolerances you don’t need an oil groove at all. At least that is my comment, others may differ.