"John Rumm" wrote in message
...
I was looking at a steel pulley block the a while ago (the type that fits
onto the end of a crank shaft on an engine and drives the belts)...

It was apparently machined from solid. The hole though the centre of the
approx 3" thick pulley was perhaps 1/2" diameter. The through hole had a
square cut slot (approx 5mm deep and wide) machined into its circumference
for a woodruff key. I was struggling to visualise how you could machine
that, anyone know?

A broach would be the usual way to make an odd-shaped hole.

http://www.culvertool.com/Products.htm

shows some of the shapes you can make with a broach.

Colin Bignell