[jyl]

I drilled decorative holes in some aluminum bicycle cranks tonight. As the holes got larger - about 1/2" - It was hard to get a smooth round hole. The bit chattered and tried to make polygonal shapes.

The end result was okay - this is just a $35 set of BMX cranks for my son's bike - but jeez I'd be unhappy if these were Campagnolo.

What is the secret to:

- Drilling perfectly round holes of diameter up to 1/2".

- Chamfering the edges of those holes, with a sharp bevel shape.

- Cutting through slots with parallel sides and semi-round ends.

- Cutting half-blind slots (i.e. recesses) with polished sides and bottoms.

Assume the material is softish aluminum, and the tools available are a Dremel and a drill press.