How to make a pickup winding faceplate that runs 'true'

[BillTodd]

how do I part the piece off? Do parting tools for mini lathes handle 3" dia material ok?

My 9" Southbend would complain about parting off a 3" bar (my HLV isn't that keen)

Your mini lathe hasn't a hope :( Just mark the outside and use a hacksaw

In fact, I'd cut the plate section off prior to turning it.

[John S]

Try and make it as long as possible even if it's only the boss length.
a 8mm hole doesn't give a lot of support and adding a grubscrew only wants to push it sideways.