Metku.net posted a tutorial on how to lap a heat spreader of an Intel CPU.

IHS or Integrated Heat Spreader is the visible top of a CPU that features the prints for processor type and manufacturing date. Usually this copper plate is more or less crooked when the processor leaves the factory and this leads to a bad contact between the CPU and the cooler. This, again, causes the CPU core temperature to rise with any cooler. This is the issue that the CPU lapping tries to overcome. In this article we'll show you updated instructions to lapping your heat spreader.

Tutorial: Lapping your CPU