Hole saws

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Woodworkers routinely cut thin soft meals by sandwiching them between two sheets of thin plywood. Use double sided tape or glue to adhere the assembly together. You can then saw with whatever power saw you have on hand. A router with a straight sided carbide bit will clean the edges up quite nicely. Use a solvent or heat to soften the adhesive and open the sandwich. Art

Use a wood like a dense particle board, bore a hole the proper diameter in the board, clamp your brass over the hole and drill a pilot hole for your router bit, rout out the inner hole. Then make a second jig the diameter of your outer cut, use a turned dowel to locate the center hole in the center of the outer ring, clamp and rout.

Aluminum routs very well, I assume brass will too, the soft metal will stick in the bit, so take light cuts and coat the bit with a good lube before, during and after.

Stuart

Get tubes with the right dimensions and turn or grind a knife edge. With the sheet on a block of hardwood tap the tube through it with a hammer.

Barring the use of a metal lathe which makes the process trivial, here's another choice:

up on Google

The local hardware store has these in two sizes on the peg, I've used them on plastic, wood and thin sheet metal. Best used in a drill press. For thin sheet metal, you're going to want to sandwich the stuff between two sheets of wood, preferably with some sort of easily removed glue or contact cement(shellac?). When I use one of these, I put a hole in the center of the workpiece with the drill bit, then swap it out for a rod so the pivot hole doesn't get wallowed out. You want to run this thing sloooow, some cheapy drill presses won't go that slow. The workpiece gets clamped, you adjust the flycutter radius for the outside and cut that first. Then do the inside. 1mm tolerance shouldn't be too hard to do, just be careful measuring and setting the cutter. I've done wooden toy wheels with one.

Stan

If you look at Abrasha's website you will see he has done just about what you are needing to do. His videos are amazing!

Barring the use of a metal lathe which makes the process trivial, here's another choice:

up on Google

The local hardware store has these in two sizes on the peg, I've used them on plastic, wood and thin sheet metal. Best used in a drill press. For thin sheet metal, you're going to want to sandwich the stuff between two sheets of wood, preferably with some sort of easily removed glue or contact cement(shellac?). When I use one of these, I put a hole in the center of the workpiece with the drill bit, then swap it out for a rod so the pivot hole doesn't get wallowed out. You want to run this thing sloooow, some cheapy drill presses won't go that slow. The workpiece gets clamped, you adjust the flycutter radius for the outside and cut that first. Then do the inside. 1mm tolerance shouldn't be too hard to do, just be careful measuring and setting the cutter. I've done wooden toy wheels with one.

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I forgot about these! I looked at them some time ago but dismissed them on account of the said cheapo drill press. However, since last month I have been a proud owner of a new drill press that goes down to 220 rpm. That should be OK for a 4-1/2" circle?

The hint about the swapping the drill bit for a rod seems crucial, thanks.

Sadly, lathe has been so far present only in my dreams...

Thank you. I had a look. Now I am depresssed. Please see the following link, not to boast but mainly to demonstrate the ever so slight difference in the level of skill.

These can be very interesting to use cutting a hole in car body metal powered by a 2000 RPM, non variable drill motor. DAMHIKT Gerry :-)} London, Canada

He is a marvelous craftsman. He is also an Idiot Savant. Good for one thing (other than composting) and one thing only.

You are multi talented compared to him, if you can at least tie your own shoes

Gunner