I have a need to make neat round holes in plywood, from 1.75 to maybe 5-6
inches in diameter. That's not for a woodworking project, it is to
make guides for plasma cutting.
I have a relatively nice Ryobi scroll saw that uses pinned blades.
What I found out was that making sure that the curvature of the cut
was constant, was kind of difficult.
I would like to know if there are any "secrets" of scroll saw cutting,
that I am neglecting.
My feeling is that I should look for a blade that is not as "deep"
(deep meaning dimension along the line that is being cut, can be also
thought of as width of the blade).
Any other suggestions will be gratefully accepted.
Thanks, I will check it out.
Meanwhile, I tried "narrower" 18.5 TPI blades (not sure of the proper
terminology), and these worked much much better. I also tried a
slightly different hand technique. My last hole is almost good enough.
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.
On Fri, 23 Feb 2007 15:02:37 GMT, Phil-in-MI <NO> wrote:
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
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
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.
In scroll saw work we number the blades. Such as #5, or #7 or #2. Also we
describe the blade's tooth system such as skip-tooth, double skip-tooth,
reverse-skip-tooth and so forth. (Most of this tooth stuff has to do with
the old bandsaw blade rule of 3 to 5 teeth in contact with the wood.) We
also WAY prefer to use plain end blades as opposed to pinned end blades like
you are using. Once you try a plain end, you will never want to go back.
You seem to be using coping saw blades, which if they work, and you get the
Job done, fine.
Most scroll saw blades you find in local store shelves are of medium
quality. There are much better blades by mail order. Pegas, and Flying
Dutchman are two brands. Please don't use Sears brand scroll saw blades.
(aside: as a personal favorite, for thick plywood I like
double-skip-double-tooth with reverse blade configuration, but them's
fightin words in the scroll saw hobby world. Man the Flame Throwers!)
IMHO: Best explanation of blade types is http://www.scrollsaws.com/ just
scroll down on the left hand side. There are other web pages that explain
scroll saw blade types and sizes, but they are associated with selling their
brand of blades.
As with any project, it is more important to get the project done than be a
"purist" of the craft. You seem to be well on your way to making do with
your templates. Therefore a hearty WELL DONE!
Now for the bad news. A scroll saw blade with too many teeth, will cause
you all kinds of grief because the gullets between the teeth are too small
and close together to remove the chips and saw dust. The chips not removed
will remain in the kerf and cause friction, which results in heat. This
heat dulls the blade. The end result is broken blades, burned wood in the
kerf, and just bad news.
Keep at it, you are doing great. The object is to make templates, not to
get confused with some obscure hobby world word play.
On Fri, 23 Feb 2007 16:44:37 GMT, "Phil-in-MI" <NO Spam &
Hurray for Phil!
Just bought a scroll saw and while my cuts are amateurishly ok, that
site has a plethora of information on proper use. Need some bandwidth
to see all the videos, but well worth it if your a scroll saw
Book marked immediately!
Thanks for the 411!
Baltic Birch plywood comes in many thicknesses from about 1/16 inch to over
1" and it comes in 5' X 5' sheets. It's high quality stuff with many thin
layers and no voids and it cuts great on a scroll saw. If you are going the
scroll saw route you might try to find a source for this near you. Cabinet
shops, specialty lumber yards, and plywood distributors are the places to
look with the latter being the best choice if you can find one. I
personally would go with a circle cutter fixture on a router and a spiral
bit as the holes will be more concentric, but it's your choice.
"Gerald Ross" < firstname.lastname@example.org> wrote in message
On Feb 22, 11:05 pm, Ignoramus19901 <ignoramus19...@NOSPAM.
If you want neat and round, a scroll saw might not be the best way to
get there. Someone already suggested a circle/wheel cutter for a
drill press. I also have had great success using a circle cutting jig
with a router. Jasper makes an excellent one, seen here...
They were originally designed for making cutouts for speakers, and
they do that excellently. Just be sure that the pivot pin is pushed
far enough in when you're making really small circles. If the collet
hits it bad things can happen.
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