Scroll saw secrets for making neat holes

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
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holes for a dog feeder. I bought a cutter that goes in a drill press from HolePro. Not cheap, but quick, easy, and accurate.
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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.
i
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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

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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 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
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I just bought some 25 TPI super fine blades on eBay, will report on how they work once I try them. 18.5 TPI blades work much better than 15 TPI, so I will try to move farther on this continuum.
i
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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.
Good Luck.
Phil
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On Fri, 23 Feb 2007 16:44:37 GMT, Phil-in-MI <NO> wrote:

Thanks Phil. I will see which blades work best, out of what I end up having.
i
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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 newbie!!!
Book marked immediately!
Thanks for the 411!
Phred
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Ignoramus9377 wrote:

If you have a Home Depot near you, they usually have partial sheets (2' x 4') of various thicknesses of MDF as well as plywood.
--
Gerald Ross
Cochran, GA
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I will check them out, maybe tomorrow.
I tried plasma cutting using my templates, it works very well. I have a Hypertherm Max100 cutter that goes up to 100 amp cutting current.
i
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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.
--
Charley



"Gerald Ross" < snipped-for-privacy@netcommander.com> wrote in message
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only time I was scared of my drill press.
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sounds like stuff to stay away from.
i
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Use a fosner bit up till about 3". Then a hole saw bits an a drill press or hand drill for the bigger holes.

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On Feb 22, 11:05 pm, Ignoramus19901 <ignoramus19...@NOSPAM. 19901.invalid> wrote:

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... http://www.leevalley.com/wood/page.aspx?c=2&p@970&cat=1,43000
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.
JP
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Looks like a great idea, though, i think, I do satisfactorily with what I have, given that I use these circles for plasma cutting.
i
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scribed:

Neat Jig. Wish I thought of it!
So it uses a scroll of insert holes to make the desired size.
Good idea.
Phred
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