On Tue, 18 Dec 2007 08:35:05 -0800 (PST), Miki
wrote:

Hi guys,

I have a project at work, it involves drilling two .600" holes into
the backplate of a heatsink and through the fins.

On the first try I plunged a .600" drill into the base plate. When
the drill was through the base plate and touched the fins, the fins
wanted to wrap around the drill and tear out of the base plate.

The heat sinks are large surface area, but the fins are only about an
inch high. They are joined to the base plate with nonmetallic
adhesive.

Is there a better way to maintain a clean cut through the heatsink
fins? They are .050" thick aluminum. Base plate is .250" thick. I
was thinking of filling the fins with Cerrosafe... don't know if this
is feasible (e.g. Cerrosafe might just push out of the fins?)

Try packing the fins with brown sugar. Pack 'em good, the stuff will
tamp a lot and become quite hard. After drilling (sharp endmil as
Gunner suggests), you can dissolve the brown sugar in hot water.

How strong is tamped brown sugar? It's used to test prototype fuze
electronics in artillery shells that experience over 20,000 G's when
fired. Retreive round, soak in hot water to remove brown sugar, check
the elex.