Lapping

From Overclocking Wiki

Lapping is the process of smoothing the bottom of a heatsink, or waterblock to create a flatter surface which improves mating with the processor. Most commercial heatsinks are lapped to a certain degree and do not require the surface to be further processed. Some of the less expensive heatsinks do require additional lapping, and are best treated with a series of fine sand papers. The use of a buffing wheel would only serve to give the surface a concave finish, and would not provide a good mating surface.

Lapping Proceedure

Materials Needed

Sand Paper - The best type of sand paper to use is auto painting sand paper. This can be found in the automotive section of most stores including Walmart, Pep Boys, or Advanced Autoparts. You will need to get at the very least: 800, 1000, 1500 and 2000 grit paper, however, most experienced lappers prefer to use 400, 600, 800, 1000, 1500, 2000 and 2500 for a better finish in the end.

Flat surface - Most people who lap heatsinks say that a piece of glass is the best surface to use since it is flat and free of bumps usually. However, any flat surface such as a marble counter top works just fine.

Water - You need water because, though you don't necessarily have to wet sand, your sand paper will get full of metal shavings and it is best to keep the the paper as clean as you can to get the best results from it. You can opt to wet sand if you so choose, just make sure that your sand paper is designed to not tear when wet.

Procedure

Step 1: put a little bit of water on the glass or surface and stick the sand paper to it. The water helps hold the sand paper down so it does not slide.

Step 2: place the heatsink base flat against the roughest grit sand paper you have whether it be 400 or 800. Proceed to slide the heatsink back and forth in the same direction for roughly 10 minutes making sure to keep pressure on the heatsink even at all times to ensure a flat surface.

Step 3: remove the low grit paper and replace with the next highest up in your stack. Repeat step 2 for 8 minutes.

Step 4: remove previous paper, replace with next one up until you reach the 2000 grit paper, each increment you go up in grit reduce your time by about 2 minutes or so until you get to the 2000 grit. Once you get to 2000 grit, flip over the 2000 grit and that will give you what is approximately 2500 grit paper. Rub it on the 2500 for about a minute or two and remove the heatsink.

Step 5: rinse of the base of the heatsink making sure that if it has a built in fan not to get the fan wet.

Step 6: Admire your work, if you did everything right, you now have a perfectly flat heatsink base to mount on your processor.

SIDE NOTES 1. When you remove the heatsink to switch your grit, be sure not to stop your rubbing motion when you lift off, just lift off in the middle of a stroke, this keeps the sandpaper from damaging the base accidentally.

2. Never touch the base of the heatsink when you are finished. The oil from your hands can effect the Heatsink's ability to transfer heat when the thermal paste is applied.

3. Always put your heatsink base facing up when you are not using it to avoid damaging your perfect surface.

4. Do not polish the base when you are finished. It is a common practice for people to use car polish on the base of their heatsinks to make them reflective, however nice this looks, it counteracts the thermal paste and yields worse temps in the end.