Originally posted by: OfficeLinebacker
In the ideal situation, the surface of the heat sink is so smooth, there are no crevices!
I honestly think the time/effort are better spent lapping/polishing the heat sink.
Actually, I've heard otherwise. Of course it is generally agreed that the primary objective of lapping is to get flat (not necessarily smooth) and for that 800 grit should be plenty. In general, people rarely report any further decrease in temps by polishing past 800; they more do it for fun and that shnazzy mirror finish.
I can't find the site now, but I read a site a while back from a guy using TIM materials to cool a laser setup and decided to try lapping at different grits. Interestingly, he found a max beneficial effect at around 600 grit and going higher actually made things worse! His theory was that the surface peaks due to roughness actually push through the TIM and make relatively direct metal-metal contact allowing better thermal transfer. In the case where the surfaces become too smooth, even though the TIM ends up being thinner on average, there is less direct contact between the metal surfaces.
But, that being said, I haven't heard of computer users reporting any problems going to higher grits, just not any benefits either. Of course, there will always be crevices unless you're using some pretty expensive equipment. Just take one of those "mirror finish" surfaces under even a low power microscope and you'll see what I mean. You would at least need to use those sub micron polishing powders to get to the next level if you really want to try it.