On Fri, 27 Jul 2007 14:09:54 -0700, "
wrote:

Then you go on to find someway to chuck the irregular work.
Now I'm left with an irregularly chucked work and a reference point on
a board clamped to the drillpress table, very closely aligned with the
drillpress spindle. What does that buy me?? - Mike
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You use a 'spud' -- anything that marries the part to the chuck in a
concentric fashion -- and use it to press the part against the tack/
center/whatever.

Once you know where the center falls you may drill & tap to use a bolt
as your new chucking piece, or attach a T-nut, centered on the new
mark, and so forth.

The purpose of the tack & cardboard is to transfer the center-point to
the opposite side of the irregularly shaped part, with the
understanding that using a tack and piece of cardboard is meant to
illustrate how the thing could be made up of whatever materials were
on hand.

-R.S.Hoover

if you used parts out of the aircraft spruce cattle dog you'd find
that there was no need to make an oddball part.
the cattle dog has the complete set of parts described in it.

....and a complete set of light weight anodised blue parts.

Stealth Pilot