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?)

If the fins happen to be the same thickness as the space between them,
clamp two heatsinks fin-side-to-fin-side. This assumes you can live with a
fin-width variation in hole location.

If they are not, perhaps you could find some sheets of thin sacrificial
stuff (plastic, wood, soft aluminium) to take up the gap.