What is the proper way to lap a heatsink?

[KCarter335]

I've seen a few suggestions on discussion boards and did a quick search for it here, but didn't really find any. Is there a standard way to lap a heatsink, or better yet, is there a "proper" way to lap a heatsink? Anyone, anyone?? Bueller?

[weazel]

Well, this is the way I do it....
I have a pane of glass that I use because it is about the flattest surface I can find...i use a fine grit wet/dry sand paper and make small circles until I can see the high spots...as the high spots go away I go to a finer paper until its as smooth as I can get it

[Gameguru]

I'm doing a tutorial for overclockers.com on that very subject. Weazel is right....you need to use a pane of glass.
I just used a pane out of a cheap picture frame and did it on my workbench.

Start with 1000grit wet/dry automotive type sandpaper.
Wet it with water and begin sanding the bottom of your heatsink with it. If you look at it after a couple of minutes, you should see high and low spots on the HS. Continue with that until there aren't any more high spots. Clean the sandpaper as necessary and keep putting clean water on it.
MAKE SURE TO KEEP THE HS AS FLAT ON THE SURFACE AS POSSIBLE!

Once this is done, go to 2000grit sandpaper and sand it until you can no longer see the scratches made by the first step.

Finally I like to take some metal polish(I personally use "Mother's") and polish the bottom.

When you are done, it should have a mirror like finish.
NOTE- Make sure to clean the polish off and wash the bottom of the HS to remove all residue.

Put a small dab of HS grease(thermal compound) on the processor and put the HS back on.

Easily 5º drop in temperature.