heatsink lapping..has anyone done it?

I've done it, but only to 600 grit. People who do it for serious performance gains (mine was just to smooth out the seriously ridged surface) go up to about 1200 grit. It can reduce temps by a few degrees but it's not usually anything spectacular.

So long as you don't end up sanding away 2 or 3mm of the heatsink you'll be fine.
 
I did my mates cpu cooler the other week. His xp3200 was idleing at 55'c and his pc keep crashing due to overheating, so I took off the heatsink and found that there where small ridges on the copper base where it was really badly machined. Took about an hour or so with some fine wet and dry to smooth the surface off. After refitting his temps dropped by 15'c and no more crashes. His base on the cooler was really bad so not sure how much difference it would make to a cooler thats base is at least ok to start off with.
 
If it is smooth to start with then i think you're best leaving it alone. I have lapped a 1900xtx cooler (which to start with was lumpy and scratched as hell), an arctic cooling freezer 64 (which was smooth) and a mosfet water block (which was as rough as sandpaper to begin with).
The temps on the 1900xtx dropped by 5-7degs, the arctic cooler stayed the same and the mosfet block was useless so never used it!!!
I use 1200 grit wet/dry and you get a really nice shine with a bit of elbow grease.
If you do decide to lap any your heatsink make sure you do it on a flat surface (it will still be shiny even if the surface is uneven but your temps will go up due to poor contact)
 
I just bought a premium lapping kit from another retailer and it came with 10 sheets of wet and dry from 400 grit to 10 micron ( :eek: ), a piece of glass to do it on and a tube of AS Ceramique. I shall be doing my waterblocks with it. In a review the kit i got done very well. The bloke doing the review got drops in temps of 8 degrees idle and 4 degrees load. He did admit that his heatsink was very rough previously. People may say it's a lot of hassle for a few degrees less but with summer coming a few degrees is a good thing. I can't give you a link to the review as they also have a link to the retailer.
 
I always question how flat and smooth the other surface is too. ie the IHS or CPU die.

What's the point in going crazy on the heatsink and making it as flat and smooth as you possibly can when you are going to stick it onto something that is concave, convex, bevelled edges or has text engraved in it????

I have lapped an NF2 northbridge before - scarey :eek:

Basically only do it if the heatsink is shockingly scratched.

It is more important to get the correct amount of TIM (arctic silver or other).

edit/ another consideration is if it oxidised it is worth giving it a quick polish (1200 grit) to make it shine again. Copper oxide is no where near as good a conductor as pure copper. Thats why a lot of HS comes with plastic you pull off before using /edit
 
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Flat is allegedly more important than shiney.

Although I still question the flatness of the surface you are mating it to, but basically you want as little thermal compound as possible between chip and heatsink but good even contact. At least you only get half the amount of ridges & voids if you can guarantee at least one side is FLAT and SMOOTH.
 
Lapping on an uneven surface would be pointless - hence the glass.

Flat is more important than shiny. Do not use any kind of polish. To check flatness, don't check whether you can see yourself cos you ain't that regular. Check the reflection of graph paper - are all the lines in all directions straight?

Also, before you start draw diagonal lines with a pencil across the base, then after the very first minute, see whether it is being removed uniformly or not. If not, your base was not flat to start with. When all the pencil is gone, stop.
 
MikeTimbers said:
Lapping on an uneven surface would be pointless - hence the glass.

Flat is more important than shiny. Do not use any kind of polish. To check flatness, don't check whether you can see yourself cos you ain't that regular. Check the reflection of graph paper - are all the lines in all directions straight?

Also, before you start draw diagonal lines with a pencil across the base, then after the very first minute, see whether it is being removed uniformly or not. If not, your base was not flat to start with. When all the pencil is gone, stop.
Click to expand...
But why glass? Wouldn't it be cheaper to use another material :confused:
 
Glass is pretty cheap ? Metal, wood or plastic are malliable to a small extent, the glass wont give and if it breaks you were trying too hard :D

Some good tips on thread, maybe I give this a go one day in front of the telly :D
 
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