I agree, boring random diameters defeats the purpose of soft jaws. You can keep re-boring/re-facing the jaws until there's pretty much nothing left, or save a couple at specific sizes for jobs you run frequently.
If you want a set of "generic" soft jaws, just bore them like a set of master jaws, either turn the jaws (face out) to put a convex surface on them, or open them up to the maximum OD the chuck is capable of and bore at that diameter. The concentricty for either of these options is horrible compared to jaws bored in place to a diameter.
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