Dave Hinz wrote:
OK, I now know several ways not to do this. Sounds simple - 4 holes,
evenly spaced, around a circle 0.600" in diameter.

The center of the circle, I can find easily (lathe & center drill). The
edges are concentric to the center, by definition, because I turned it
on that lathe.

I marked the 0.600" circle on the face of the disk by lightly touching
it with a cutting tool on the lathe & turning the work around, scribing
a circle at the right diameter.

Now, how do I get the 4 points layed out properly from there? I can use
a center finder to get two of 'em, but how do I get the other two evenly
spaced from those points? Or, worse yet, what if I wanted 3, or 5 holes
on that circle, rather than 4?

Dave Hinz


You can do it with a divider- make two arcs of nearly the diameter from
the center of each hole you've established (distance is unimportant, as
long as it's equal from both holes) and the interesections of these arcs
will be on the diameter perpendicular to the one you're starting from.

IIRC a chord of 1/2 the radius reaches one sixth of the circumference
from the starting point.

Dunno how to do five or seven, hope someone else does 'cause I've always
wondered how to do it.

For working with the torch/plasma cutter, a string and soapstone can do
pretty close work in dividing circles.

John