How do you lap a heatsink?

S

scrawnypaleguy

Limp Gawd
Joined
Apr 11, 2006
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I've heard of lots of people doing it, and it seems that it can greatly improve the looks of your heatsink, but how is it done? Does it take a long time? Will I see an improvement in temps?
 
Unless you're using a nice heatsink, you'll probably notice a few 'c temp difference. The best way to do it is go steal a pane of glass from somewhere, like a pictureframe (real glass now). Place your sandpaper on top of the glass, and slide the HSF over the sandpaper with even pressure, at a moderate pace. Start at about 200grit sandpaper.

After about 5 minutes (1-2 hundred strokes in the SAME direction each time, no circles), gradually move up the sandpaper grit. Go to 300, 400, 600, 800, 1500 (then flip the 1500 over and use the back, it's about 2000grit). Each time you move up a grit you can shave 1 minutes off the lapping time (so about 2 minutes for the highest grit). I like to wet the glass first, before I apply the paper, so that it sticks (and gives me more traction). Always hold the paper as you slide the HSF over it too. This method gave me a 4'c idle, 6'c load difference on my stock 3800 HSF, before I went to water.
 
how polished does the bottom look? the point of lapping isn't to make it look nice and reflecty, it's to make it smooth so there's better contact between the heatsink and the cpu. shiny/reflectiness is just a side effect of metal being smooth :p
 
there are some nice kits out there too, that include glass and all the paper you will need.
 
some of you have it wrong. lapping isnt to make it shinny, its to make it as flat as possible. It doesnt matter what heatsink you have, it is NOT flat. i can guarantee that. if you guys want some pics of lapped heatsinks or cpu's i can post them.


 
joeynuggetz said:
Hows about using a dremel with a polishing wheel :) j/k
Click to expand...

I saw a forum where that was suggested, and the poster was serious! The flaming that ensued was harsh but well deserved!
 
My XP-120 was definitely not flat when I got it. Lapping helped quite a bit. My temps went down by maybe 2-3C. Not much, but enough to be worth lapping. Using water on the paper made the job easier. Just be patient and take your time to do it right.
 
Ok seriously. I'm hearing a LOT of conflicting advice on how to lap... some people say to go in a straight line the whole time and don't go in circles or anything, and some people are telling me to rotate my heatsink often while lapping and do figure 8's :confused:

What exactly should I do to flatten out (not make shiny, i want flat ) my new Scythe NInja???
 
scrawnypaleguy said:
I've heard of lots of people doing it, and it seems that it can greatly improve the looks of your heatsink, but how is it done? Does it take a long time? Will I see an improvement in temps?
Click to expand...

Dance around it?! J/K
 
you hold it gentaly in your hands, light some candles, but on some berry white and slowly lick the base of hte heatsink, you know wer done when the fan is turning so fast it whistles at ya
 
THe only time you should rotate is between grits. So the first grit level you use, stroke it in the same direction the entire time. Move up one level in the grit scale, and rotate the stroke direction 90 degrees, so the "scratches' youre putting in your heatsink are perpendicular to the ones you did on the previous grit. Next grit scale, stroke the direction of the first grit, and so aon. Each time you move up in grit you should stroke perpendicular to your previous direction.

Essentially you're just wetsanding. No one's mentioned the word yet, so maybe you all are dry sanding it? I've never tried it that way, doubt it matters.
 
And as with all things in life, stroke it gently without applying very much pressure.
 
I lapped my stock HSF, dropped it about 5c load and 3c idle, very worth it. You want to go straight, no fancy figure 8's or circles.
 
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