On Tue, 05 Jul 2005 15:55:20 -0500, Rex B wrote:
Dave Hinz wrote:
On Tue, 05 Jul 2005 13:16:04 -0500, Rex B wrote:

Get the two marked with a sharp punch, then use a compass to scribe the
other two.


I thought of that...right after I drilled & tapped the first two holes.

That makes it a little harder. I suppose if your tapped holes were
tight, you could chuck a bolt into the lathe and center drill a small
hole, then screw one into each hole flush to locate the compass.

Well, they're 10-32, and I have the grub screws to go into them, so
there is a good center to reference off of there... but that piece is
done but not perfect; the next one I'll lay out entirely before
starting.

So, that would really work with any number of holes; once I have the
circle diameter known and marked, pick a point, determine the spacing,
and walk it around the circle. If I didn't screw something up, it'll
all line up to the original hole when I get all the way around - yes?

With just 4 holes it's actually easier than that. Quick trial & error
until both arcs intersect at the circle scribed earlier.

So scribing the circle as I described seems to be the way to go if I'm
going to use the lathe to mark things - if I use it on the mill (if I
can figure out how to hold the darn thing) then it's a case of convert
it to X/Y coordinates and poke the holes where they belong. While I'm
not quite sure that I'm confident enough to do it that way without a
layout circle to double-check my work, maybe that'd be a good
experiment. Scribe the circle with the lathe, and then use the mill as
if that circle wasn't there, and make sure the holes are on the circle.

Oh darn, another evening in the shop. Maybe the next one will look
more presentable

Dave Hinz