Lapping is a procedure whereby using one surface is used as a reference and another surface is used as the comparison. One puts a layer of fine abrasive slurry between the surfaces and "rubs them together" so that the one becomes as smooth as the other.
Intake and exhaust valves are often lapped against their seats so that they mate well.
Any situation that calls for one surface to be mated to another could be lapped. The issue of "to lap" or "not to lap" can often be primarily about the technicalities of space and fit as much as about the results.
Perhaps the most important thing to know about lapping is that it is a proceedure intended to make things fit togther in a specific way. |