The Cake Tin

I have a 7" cake tin and wish to drill a hole in the dead centre, but the edge of it is rounded, and therefore imprecise to score
lines from. It is too big to put in the 4-jaw.
Suggestions, ideas, please?
(It is intended as the tuning drum of an unusual design of radio receiver)
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"gareth" wrote in message

Place on rotating table like a record deck - centralise by gently touching with a finger, mark centre with Sharpie felt tip marker as it turns - you'll get concentric circles which you can reduce to a point by moving the Sharpie
Andrew
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On Thu, 13 Mar 2014 22:36:10 -0000, "Andrew Mawson"

Other methods:
a - turn a disc of scrap ply or something to just fit inside the lid, drill guide hole, remove, use, discard.
b - give to a potter who can use the record deck method with the lid on a lump of clay on a wheel - much less likely that it will shift during the process; and if they are good will do a far better job of centring by feel than anyone who's not a potter.
c - clear discs with concentric rings and a central hole are made for just this purpose - just as easy to make as a and useful next time as well.
Though if you're using a cake lid as an element your tolerances can't be all that tight...
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au contraire, it seems to be as round as any of the tuning drums from old radios.
This cake tin has cylindrical sides
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Sorry about having possibly wasted your times, chaps, but with the thinking cap on, the solution has presented itself, and that is, in order to attach to the shaft of the tuning condenser (Yes, it's an old one from the days before they were known as, "capacitors" :-) ). some form of bush is needed; therefore, machine the bush as a solid lump, but without a central bore, attach to cake tin, grip the now-salient bush in the 4-jaw, true up on the circumference of the tin; then bore both together.
... but thanks for your thoughts, anyway.
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