Lapping Guide for CPU and Heat Sink

Why lap?

The benefits of lapping have been well documented by overclockers and will normally result in lowering CPU operating temperatures a substantial amount. Lapping ensures flatness on the surface of the processor and on the base of the heat sink. When both are perfectly flat, heat transfer is more efficient because the contact area of the two surfaces is maximized.

Lapping will probably void any warranty so before you start lapping on your processor please consider the risk. If you’ve decided you are willing to take the risk then please continue.

The process of lapping both the processor and the heat sink will require about 4 hours. This process is not for the impatient. The cost to perform these procedures was approximately $20 USD.

Lapping the Processor

Use the safety cover to protect the contacts on the processor. The processor must be lapped on dry sandpaper.
Follow the steps in this illustrated guide. Use care not to use any pressure on the processor when lapping; let the sandpaper do all the work. Take your time and take frequent breaks. Lap with progressively finer grades of sandpaper until a flat smooth surface is obtained. Note that flat is much more important than smooth.


Lapping the Heat Sink

The heat sink is lapped on wet sandpaper along with a small amount of dish washing detergent placed on the base to provide additional lubrication.

Additional patience is required when lapping the heat sink. This is because the surface area is larger and
also because of its bulkiness. The high centre of gravity will also make lapping more difficult because it leads to instability that promotes chattering. Start lapping with small short back and forth strokes. Pause between strokes to keep the inertia from tipping the heat sink at the end of each stroke. It’s very important that each stroke be carried out smoothly.

You’ll notice that the heat sink will tend to chatter on the paper until you find the right combination of force, moisture and dishwashing detergent. Add a small amount of detergent frequently until you find the combination that will allow you to slide the base back and forth smoothly without any chattering.

Installing the Processor and Heat Sink

Thoroughly clean the lapped surfaces of the processor and heat sink with a clean rag dampened in Acetone. Do not use any type of petroleum based solvents.

DO NOT GET ANY ACETONE ON ANYTHING OTHER THAN THE LAPPED BASE

When installing the heat sink and processor use a quality interface like Coollaboratory Liquid Metal Thermal Interface Material or Artic Silver 5

Continue at your own risk



Things you’ll need. A piece of glass, duct tape, felt-tip marker, wet or dry sandpaper: 320, 400, 600, 800, 1000, 1200, 2000, 2500 grit. The coarser grits can be found at Wal-Mart and the finer at NAPA stores.


Nickel plated Intel Core 2 Quad processor as received before lapping. Lapping will likely void any future warranty.

Marking the top of the processor with a felt-tip marker before lapping will aid in evaluating the flatness of the surface.

Mark the base of the heat sink in the same manner as the processor was marked.


Secure the glass to a flat surface with the Duct Tape


Place a piece of dry 320 grit sandpaper on the glass and lap the processor in a figure of eight pattern. Rotate the processor by 90 degrees after the completion of every tenth pattern. Do not use any pressure. Easy does it!

After five minutes of lapping with 320 grit you can see that the surface of the processor was convex rather than flat. Continue with 320 grit until the copper base begins to show.

After fifteen more minutes of lapping with 320 grit you’ll begin to see the copper base. Switch to 400 grit paper and continue lapping.


After 20 more minutes of lapping with 400 grit you can see more progress but it is still not flat. When all of the Nickel plating is gone switch to 600 grit paper.

Continue lapping with finer grits to remove scratches. After 30 minutes of lapping with 1500 grit the surface is now flat and most of the scatches have been removed. Finish now with 2000 and 2500 grit.


Lapping the heat sink requires even more patience. Begin with slow back and forth motions and finish with a figure of eight pattern. Keep the paper wet, use detergent and avoid chattering.


This heat sink base is also convex like the processor. The base of the heat sink is lapped in a similar manner using wet sandpaper and a small amount of dishwashing detergent as a lubricant.


After 30 minutes of lapping with 320 grit most of the plating is gone. Continue with 320 until it is all gone and then switch to 400. It was suprising that this base wasn’t manufactured flatter.

The surface is now flat. Now continue lapping with progressively finer grades of wet sandpaper to remove scratches.


The finished products should look something like this.

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