Get one of these "Jasper Jigs" and attach to your router. If you don't think you'll need it again in the future, you can make an oversized router baseplate from scrap hardboard, and drill the pivot point so that it will give a 6" circle.
Get one of these "Jasper Jigs" and attach to your router. If you don't think you'll need it again in the future, you can make an oversized router baseplate from scrap hardboard, and drill the pivot point so that it will give a 6" circle.
My first circle jig was nothing more than a 6" wide strip of hardboard mounted to the base of the router. Drill a 1/4" hole in the center of your hole location, stick a dowel 3" from the far side of the router bit through the hardboard and into the hole in the ply and start turning.
Use the fence Luke
Jasper jig.
While the router mounted circle jigs are great for making round discs, I have to think it's very easy to mangle the cutout. There's nothing keeping the disc/router from drifting into the sheet as you finish the cut. Is it just a matter of being careful, or is there a trick for getting the cutout to come out perfectly?
The trick with double sided tape is use enough to do the job but not too much and most importantly don't leave it stuck any longer than needed to get the job done. In most cases, the longer tape is on a surface the tighter it grips. Don't place any tape near a cut edge and always peel the tape off toward the cut edge not away from it.
Lee Schierer
USNA '71
Go Navy!
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A fly-cutter catch is worse than a hole-saw catch.
I've never had a problem using a large hole saw, even with a modest drill, as long as you don't lean on it. I wouldn't expect a cordless drill to do very well, however. Keeping the RPM up will minimize any tendency to catch.
Having said that, 6" is a reasonable size to cut with a router, as well. A router will take longer to set up and cut, but you will get a cleaner hole.
Awhile back, I had several circle cutouts to do and was concerned about that exact problem. My solution was to use a piece of plywood larger than my workpiece, drill and insert a 1/4" dowel at the center of the plywood, attached an auxillary block with a 1/4" through hole to the router's edge guide.
A 1/4" hole at the center of the cutout in the workpiece fit over the 1/4" dowel in the plywood base, and the hole in the edge guide fit over the dowel on top of the workpiece. Edge guide adjustment set the radius of the circle. Clamped the workpiece to the plywood base, routed the circle. Clamp restrained the workpiece, dowel restrained the center cutout, plywood base protected my workbench. Use the same tooling for every circular cutout larger than my router baseplace.
Tom Veatch
Wichita, KS
USA
The reason they don't make hole saws larger than 6-1/4" is that the torque required to drive them is well beyond the capabilities of any hand held drill. Even the mighty Milwaukee Hawg stud drills are rated for a maxium hole saw size of 4-5/8 in wood.
We use a Hole Pro adjustable hole cutter that we first saw on "Cool Tools" and with it we can easily cut 12" diameter holes in MDF and plywood using a 1/2" hand drill with now problems and get a much cleaner hole in a lot less time as well. Twin blades make for less contact area so a lot less horsepower is needed and their is no burning of the wood and you won't spend another 5 minutes knocking out the plug when you are done.
Good for laminates and plastics as well and no worry about needing an ultra low speed to prevent melting as with hole saws and similar tools.
You can also make the hole exactly the size you really need, 6-1/4, 6-3/8, 6-7/16, no problem. But use a twin blade cutter as the single blade tools are not very good and are very limited in their cutting range. We usually use the Hole Pro model X-305 that adjusts infinitely from 1-7/8" up to 12" as we do speaker and home theater cabinetry and are often working with MDF (which rapidly dulls bi-metal hole saws).