Sandpaper for lapping. Which one?

I am ready to lap my heatsink and also my ramsinks. I went to Home Depot to try to find some 600 and 800 sandpaper. All I could find was some lower grades like 60 or 100. Those were extremely rough. The highest I could get was 400 and that was very fine but showed it was for water proof for wood or furniture.
Is there any other place I could get this or would the 400 be ok?

dolemitecomputer said:

I am ready to lap my heatsink and also my ramsinks. I went to Home Depot to try to find some 600 and 800 sandpaper. All I could find was some lower grades like 60 or 100. Those were extremely rough. The highest I could get was 400 and that was very fine but showed it was for water proof for wood or furniture.
Is there any other place I could get this or would the 400 be ok?

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As a matter of fact, I just got back from Home Depot not more than 5 minutes ago, and guess what I bought? 2 packages of sandpaper, a 220 grit for wood, and a 600 grit wet sandpaper, both for use on my RAMsinks and GPU HSF. You could get 300 instead of 220 though, if your HSF is not anodized on the bottom.

The 220 grit costs $1.74, and the 600 grit costs $2.74.

Sandpaper is in the painting section, in case you were in the lumber section. There should be dozens upon dozens of grains and purposes available. If your local Home Depot doesn't have 600 grit waterproof sandpaper, go to the next closest store, it's worth it for a good lapping.

600 grit is the ideal number, anything more wouldn't really be beneficial enough for the effort, as you'd still need to use 600, then continue with a final sanding using 1000 grit. Alot of effort can be done without if you skip the 1000 grit.

If lapping doesnt take you at least 30 minutes, you aren't doing it right, or not doing it long enough with each grit. It should take you about 10 minutes with the 220 grit, and another 20 or so using the 600, with water on the 600.

Besure you do it in an ABSOLUTELY FLAT surface, or you'll end up with glass-smooth edges, and a non lapped center, or vice versa. Some people get a pane of 1/4" or 1/2" glass about 12" x 10", and tape the sandpaper's edges to that. I am lucky enough to have a solid oak desk which happens to be completely flat, having been planed properly. Don't just do it on a coffee table or a bridge table, you'll regret it. Try to avoid doing it on soft surfaces like plastics, rubber (duh) and soft woods like pine.

If the heatsink you're lapping is anodized on the bottom, use a file to get the anodization off before you start to lap it, lapping anodization off can be quite a chore (This is where the 220 grit comes in, it can help you get rid of the file marks that you might accidentally gouge into the metal).

400 Grit isn't fine enough. I suggest starting with 600 Grit. Just in case you didn't know, you want wet 'n dry sandpaper. Occasional dabs of water help clean used grit and powdered aluminum/copper out of the "pores" of the sandpaper. You want the surface of the sandpaper to be wet at all times.

For finishing the job and in aid of a mirror surface on the business end of the HS, I wouldn't use less than an 800 Grit sheet of sandpaper. In fact, 800 Grit won't give you a mirror like surface. You need to step up to 1000 Grit, or even 1200 Grit.

This is a job that should NOT be rushed. Set aside a couple of hours for the task. It is a labor of love, after all.

The place to get this very fine wet 'n dry sandpaper is an auto supply store. An auto-body supply store is even better. It's expensive, btw. I don't think you can get it for a buck per sheet. More like two or three. C'est la vie.

klosters64a said:

400 Grit isn't fine enough. I suggest starting with 600 Grit. Just in case you didn't know, you want wet 'n dry sandpaper. Occasional dabs of water help clean used grit and powdered aluminum/copper out of the "pores" of the sandpaper. You want the surface of the sandpaper to be wet at all times.

For finishing the job and in aid of a mirror surface on the business end of the HS, I wouldn't use less than an 800 Grit sheet of sandpaper. In fact, 800 Grit won't give you a mirror like surface. You need to step up to 1000 Grit, or even 1200 Grit.

This is a job that should NOT be rushed. Set aside a couple of hours for the task. It is a labor of love, after all.

The place to get this very fine wet 'n dry sandpaper is an auto supply store. An auto-body supply store is even better. It's expensive, btw. I don't think you can get it for a buck per sheet. More like two or three. C'est la vie.

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You really don't need a mirror finish on a GPU HSF or RAMsinks. A mirror finish is only nessecary on a CPU HSF.

Great. Thanks for the help. Looks like I'll head down to an auto parts store like Pep Boys or something to try to get 600 and 800 grit paper if Home Depot doesn't have it.