What's Your Method?

[cabinetman]

This is like - how would you do it. As in this thread, lets assume the medium is 1/4" masonite, plywood, or plexiglas, to make a "washer", 2.5" OD and 2" ID. I had a questionable process offered on another forum, and thought it might be interesting to see the input here. State your process and tools/aids you would use.
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[Knottscott]

My first thought was to use a hole saw...ID first, then the OD, but I think you'd need to get creative for the guide bit on the second hole.

[crokett]

I would use a router and jig. Cut the ID hole, then cut the OD hole.

Actually I would just go get the vented siding (has holes in it) that is made for this. I have it on my house.

[jrnewhall]

I made a circle cutting jig for my 10" bandsaw. On plywood or MDF I would use that with a 1/4" blade for the outside cut. It uses a 1/8" centering pin so the same hole used to make the outside cut would center a Forstner bit or hole saw for the inside cut.

Those adjustable hole cutters with the cutting blade on an arm might actually work better on the plex than a saw blade. They're not too expensive and might be worth trying just to see what you get for results.

~JRN

[cgallery]

I'd also use holesaws, but carbide-tipped ones. Using even bimetal blades would be a PITA.

And instead of using the hole saws in a drill press, I'd be inclined to use them in a large, hand-held drill. I'd make a large circle blank with the larger hole saw, then place it in a hold down and use the pilot hole to cut the concentric inner hole out.

The carbide-tipped hole saws aren't inexpensive, but on a project like this I'd chalk it up to overall money saved doing the job myself.

[Uncle Cracker]

Two easier ways to use hole saws:

1) In a drill press, with the stock clamped to the table, cut the inside hole first, then you won't need a pilot hole to cut the outside diameter; just leave the stock clamped to the same spot on the table.

2) with a hand drill, clamp a scrap piece of ply to the back of the stock, drill the inside hole, and use the pilot hole in the scrap to locate the larger bit to drill the concentric outer diameter.

[poolhound]

I would probably cut the inside hole on the DP with hole saw/cutter or forstner. Then cut the outside circle on bandsaw.

[Black wallnut]

Place another x in the hole saw column. Outside first then inside. Although David has a great point. Why not just buy the premade vent.

[JR]

I'd use one of those adjustable-diameter circle cutters. Cut the inside circle, then cut the outside circle, out pops the washer.

The trick to the question is that a 2.5" hole cutter will cut an outside diameter of 2.5", but leave the washer outside diameter at 2.5" minus the kerf.

JR

[JimD]

I would cut about halfway thorugh on the larger diameter with a hole saw then switch and cut the smaller hole all the way through and then switch back and finish the bigger one. You need a backer for the pilot. I've done this before (in wood) and had problems if I didn't start the bigger hole first. If you do the bigger one all the way first, how do you hold the piece to drill the smaller hole? There's a little material there but not a lot. Best to me is to go big, small, then finish big. The partial big hole helps guide the hole saw while you finish that hole.

Jim

[cwithboat]

http://www.holepro.com/
Use the drill press and the circle cutter. It is easier to cut the small hole first. Adapter for dust collection.

[Tom Slick]

I've got 3 methods I'd use depending on how much of a hurry I'm in, what tools I have, and how much precision I need
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Method 1: (fast)
I'd use a holesaw for the both the ID and OD. ID first with a regular arbor/pilot then the OD using an "oops" arbor/pilot.

Method 2: (fast)
Cut the ID first with the holesaw, rough cut the OD with a bandsaw, then sand the OD to the correct size and shape.

Method 3: (accurate)
Make a simple jig with a hole larger then the OD and an insert for the ID. Using a bushing and the insert I'd cut the ID first then remove the insert and then using a bushing, cut the OD.

[Russianwolf]

I would screw a scrape block onto a face plate and use doublestick tape to attach the washer blank to it. Then I would turn both the inside and outside diameters needed using calipers to check.

Then a sharp chisel to separate the two and viola.

[drumpriest]

Make the washers slightly less than 3/4", maybe 5/8". Then use any method you like to make circular trenches, I'd probably go with a router and template. Trench down 5/8", leaving enough material that the whole deal holds together.

Then resaw the board on the band saw, and the washers will pop right out.

[dbhost]

Okay, so on the Drill Press, clamp the work piece down, with a sacrificial piece under it to keep the bit out of the table, using a carbide hole saw set, which I am fortunate enough to own, running the DP nice and slow, I would cut the inner circle first, then the outer. As far as Acrylic Goes, I won't even guess. That stuff is a PITA to work with...