On Jul 13, 6:13*pm, Jim Stewart wrote:
Jim Wilkins wrote:
...

Somewhere in my dusty library, I have a book that
takes your procedure one step further. *It described
methods for making tooling fixtures for manufacturing
timepieces. *X and Y were located by stacking Jo-blocks
between stops and the tooling fixture.

The old guys were pretty clever.

That's more work. You have to clamp two bars to the mill table or
lathe faceplate and set them square to each other, then locate the
hole nearest the corner under the spindle axis somehow. Maybe you
center drill it and hold it in place with the mill or tailstock
spindle while you clamp on the bars. Subsequent holes will be spaced
by the accuracy of the Jo blocks, minus any user error or clamping
distortion.

The blocks in my set aren't really long enough to guarantee that the
work piece won't tilt.

I've used the watchmakers' disk method to drill locating pin holes for
the wedges for a pie chuck. The method worked well enough but it's
very difficult and tedious, involving turning three identical disks to
better than 0.001" diameter accuracy and identifying when they barely
make contact with one on a locating dowel pin in a previous hole and
the other on a pin in the drill chuck. Of course I had to drill the
hole without the disk in place to preserve its ID. The chuck locating
pins they had to fit onto are 0.125" diameter and 1-5/32 (1.15625)
apart. The three spacing disks I made measure 0.5814", 0.5815", and
0.5813".

jsw