ArtMetal

I am looking for recommendations for the correct tools and techniques for fabricating a small brass piece for a wristwatch concept.

The brass piece is about 35 mm diameter, .05 inch thickness. A small window (5mm high by about 20 mm long) has to be cut out of the brass disc.

So, my first thought is to cut the disc from a brass sheet with a "compass" style cutter that I found at the local hobby shop. But, how do I finish the edge of the cut to be as close to a perfect circle as possible and a nice clean (not rough) finish?

How to cut the window? I thought of starting with a 2 mm drill (corners of the window can be rounded) then sawing out the cutout and filing to finish?

Looking for tips, tools, tehcniques, on line references, whatever I can get.

Thanks in advance..