On Fri, 23 Feb 2007 15:02:37 GMT, Phil-in-MI NO wrote:
Scroll Saw is an eye - hand type of thing. A learned skill that takes
practice. Not a large learning curve, and it don't take long, but it does
take practice. Basically no jigs or fixtures to buy. Wood is free hand
moved past the blade.

Neat round holes are very hard to do. Advanced scroll saw user technique.
Takes a lot of eye-hand movement to hand feed the wood past the blade in a
smooth constant feed-rate, and constant turn. Not easy to do.

Everyone knows about blade drift, or lead, with a bandsaw. The blade wants
to cut slightly off center. With Scroll Saw, the blade drift changes by a
degree or two as you use the blade.

A scroll saw is just a motorized coping saw. May I presume you tried to
cut fat of the line and use a spindle drum sander to sneak up on the line,
but found that technique not satisfactory for your own reasons?

Another reply suggested a drill press 'circle cutter' tools. I agree. Be
aware this are real bad news on the bones in your hand if you are not full
focused of what you are doing. Please don't loose concentration when you
use these types of tools.

Phil, thanks. Lots of wisdom here. First of all, I get satisfactory
holes now, after switching to a thinner scroll saw blade and getting a
little more practice. I will look out for even smaller blades that
allow for sharper turns (are they called fretting blades??? Any
suggestions?)

These holes are guides for plasma cutting of steel. I would lead my
torch along the plywood. Plasma cutting, itself being a relatively
medium accuracy process, does not require perfect holes (since it
would produce imperfect result anyway), so I think that if I stay
within 1/2mm or so, and the hole is relatively smooth, I will be
fine.

I made a hole yesterday and I will try using it as a template tonight
to see how it works.

Ideally I would like to find 7/16" or even 3/8" thick MDF instead of
the crap plywood, though 1/2" plywood will also work.

I think that plasma cutting profile cuts, using scroll sawed plywood
as a guide, is a good start for decent hole and profile cutting.

i