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'lapping' a heat sink?? Huh?

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February 21, 2002 7:30:23 PM

I have read where people have talked about 'lapping' a heat sink to make the surface smoother and therefore have better contact with the cpu..... what exactly is this.. and how do you do it???? Do you need special tools or supplies?

Thanks in advance

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Anonymous
a b à CPUs
February 21, 2002 7:48:54 PM

Take your fan off and run down to a local machine shop.
They will do it for you for a nomimal fee.
It is simply machining the bottom of the HS so that it is flat and smooth. There are special machines to do this right. If you want to just buff out a shine than a simple car buffer will do the trick.


First time I powered up my 'puter my wife asked "Where's that swarm of bees?"
February 21, 2002 7:49:25 PM

Apply tongue to the HS liberaly.

Seriously, what most people use to "Lap" their HS a thermal compound, such as Arctic Silver II. Apply a thin coat to the HS and then put it on, and that fills any tiny hole or cracks that would prevent full conectivity.

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If your computer is smoking, please extinguish it immediately.
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February 21, 2002 8:06:22 PM

Lapping basically replaces thermal grease. Just use thermal grease (such as Arctic Silver 3), and you'll be fine.

<font color=orange>Quarter</font color=orange> <font color=blue>Pounder</font color=blue> <font color=orange>Inside</font color=orange>
February 21, 2002 8:16:54 PM

You use finer and finer grit sand paper. Start with 220 grit. Some people go all the way down to 1000 or 2000 grit but I read somewhere that 600 grit is as far as you need go but it's up to you. The finer grits go quickly anyway.

The key is not to just get you heatsink smooth. You want it perfectly flat. Lay your sandpaper on a piece of thick glass. Tape it down. Color the bottom of the heatsink with permanent magic marker. Sand in back and forth motion (or even just one direction). Use a few drops of water. Wet sanding works better and faster. Blot away the water and use clean water frequently. Make sure the heatsink stays flat and level while you are sanding. Keep sanding until all the ink is removed from the bottom. (You'll be surprised how "dished" a heatsink really is. This keeps it from making good contact with you CPU's core or heatspreader). Keep in mind that it's the middle of the heatsink that needs to be flat. If you have any imperfections away from the middle don't worry about it. Switch to the next grit and mark your heatsink again. Keep going until you get to your final grit. Wash your heatsink well. (You don't want metal dust getting into your motherboard later). Wipe the heatsink with a lint-free cloth because you don't want fibers getting between your heatsink and CPU. That's it. Pretty easy. It's worth about 2-3 degrees better cooling, more if your heatsink is in really bad shape. Some are very smooth but most aren't perfectly flat, which as I already mentioned is the important thing.

<b>We are all beta testers!</b>
Anonymous
a b à CPUs
February 21, 2002 10:03:46 PM

Hey yeah, this mothed should work good. Just don't go and use your motorized belt sander out in the garage. You want the overall HSF assembly to be flat of course, but you also don't want have a flat sloping bottom where the HSF assembly is now sitting at a funny angle, so the clip might be exerting weird pressure to the socket.


First time I powered up my 'puter my wife asked "Where's that swarm of bees?"
a b à CPUs
February 22, 2002 2:51:36 AM

Artic silver is not that good! I got more reduction from buffing my heatsink (using Radio Shack paste) than from changing to Artic Silver II.

What's the frequency, Kenneth?
a b à CPUs
February 22, 2002 2:55:49 AM

Many people want to make their heatsinks smooth and flat. They use fine sandpaper on a flat surface to accomplish this. But I've found that most CPU dies are CONVEX, and most heatsink CONCAVE, to a VERY SMALL degree. So the slight curvature is an aproximate match. I have had VERY GOOD results from BUFFING the deep scratches out of heatsinks with a scotchbrite pad and a light abrasive cleaner, without going to the trouble of flatening the heatsink (lapping).

What's the frequency, Kenneth?
February 22, 2002 3:13:09 AM

ignore the re:... lazy again

When I remove the heatsink I can read the CPU info on it. guess that mean it's touching right. no clue what's wrong with my paste, every time I remove sink there is no more paste (only a tiny little ammount left), somebody come licking my core while I'm sleeping. LOL (yeah joke) Going to buy artic silver and see, using no name brand paste, but tonight I put on some from the bag that comes with the blue orb.

<font color=red>Handsome A7V133 looking for long term relationship with a XP CPU. Prefer non smoker.</font color=red>
February 22, 2002 3:42:10 AM

A friend of mine replace his thermal pad with Arctic Silver II the other day; his CPU temp dropped 8 degrees. Replacing the thermal pad on cheap heat sinks with Arctic Silver II IS that good.

"Ignorance is bliss, but I tend to get screwed over."
a b à CPUs
February 22, 2002 4:29:17 AM

Some TIM is worse than others. I have seen similar results with Radio Shack heatsink paste in situations like his. He can probably drop another 3 degrees simply by buffing the bottom.

What's the frequency, Kenneth?
a b à CPUs
February 22, 2002 4:41:11 AM

a BLORB! UGH! Orbs do not make good heatsinks, but great paperweights! Anyway, yes, if your paste is goon, chances are it got squeezed out, which indicates a good contact.

What's the frequency, Kenneth?
February 22, 2002 5:43:43 AM

That's bad information!!!




They make lousy paperweights! :smile:

<b>We are all beta testers!</b>
February 22, 2002 8:03:52 AM

Lapping is very useful. You lap the HeatSink to make it "FLAT". The retail sink that came with my Duron was not flat, had the thermal pad and deep scoring marks underneath it. Now, it is flat. A flat piece of glass different grades of sand paper, some tape and a little time while watching the toob. It is almost mirror shiney but it is flat. I use Arctic Alumina and it is okay.

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February 22, 2002 3:27:20 PM

Remember that the Blorb is the GPU/chipset cooler, not a CPU cooler. They work ok for that, as does the Crystal Orb.

<font color=orange>Quarter</font color=orange> <font color=blue>Pounder</font color=blue> <font color=orange>Inside</font color=orange>
a b à CPUs
February 23, 2002 12:24:05 AM

Yeh, er, forgot. Actually all GPU/Chipset coolers suck, the Blorb sucks a little less because it has a larger fan. But then I have a 50mm 6000RPM CPU cooler mounted to the formerly passive heatsink on my Radeon LE, and this puts the Blorb to shame.

What's the frequency, Kenneth?
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