Milling: creating a smooth end finish in a slot

[Rob Meades]

To conclude this thread, I've now managed to cut the brass maze successfully. The secret was, as you probably expect, cooling. With a 1 mm internal diameter copper tube backing 2 bar of air pressure (no water, too messy for my loft) from a Jun Air compressor, cutting for 10 hours caused no damage to the bit whatsoever and the finish in brass is as good as that in perspex. I only applied the cooling during the looong cut around the side of the maze so as not to overheat the compressor but that was enough. Happy milling Christmas everyone!