In , on 07/05/05
at 09:44 PM, Dave Hinz said:

Rotate the chuck to the next jaw & repeat using the same prop.
Result 4 marks evenly spaced on the PCD. Use a 3 jaw chuck for three
holes, marking once per jaw. 5 holes - use a 5 jaw chu.... now you are
back to trig GG

Well, maybe having those degree markings on the chuck makes the trig
unnecessary... however, none of these methods involve making or buying
more tooling, so I'm not sure I've hit on just the right one yet

OK then, once you've done the scribing, rotate the toolpost ( if a two or
four way ), or use another toolholder if you have a QCTP. In place of a
tool, insert a bit of 1" sq. bar through which you have previously (note
the catch?) drilled a hole using a 1/4" drillbit held in the lathe chuck,
thereby ensuring the hole is exactly at centre height. Once drilled, mark
the top of the bar ao it never goes in upside down. Now you can bring this
up to your marks with a 1/4" body centre drill inserted & use the cross
slide to position the centre drill on the PCD. Turn the centre drill with
a cordless drill to start each hole, then complete on the drill press. Or
you could make a Dremel mount to fit at centre height in the toolpost &
drill the holes directly with that Or
George Thomas' book the "ME Workshop Manual" has plans for a toolpost
mounted hand turned spotting drill.

Or, if you are brave enough, try " Sigh... what I really need to do this
easily love, is a jig borer. There's one on Ebay in Czechoslovakia for
only $1500. We could spend a week there, I hear the Skoda works is worth a
look"

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