The term “lapping” is used to describe a number of various surface finishing operations where loose abrasive powders are used as the grinding agent at normally low speeds. It is a process reserved for products that demand very tight tolerances of flatness, parallelism, thickness or finish.

One or more parts are machined at the same time in a batch process. The abrasive is usually mixed with a liquid vehicle, either oil or water based. The pieces being lapped are captured in retaining rings. Workholders also called "carriers" may be used to keep the parts separated to prevent damage to their edges. The parts are dragged across the lap plate surface on to which the abrasive is being fed.

Lapping is an averaging process in which the greatest material removal occurs where the high points of the work piece surface contact the flat laping wheel. The object is to produce parts with a uniformly smooth and flat surface. A surface that has been lapped exhibits a dull, non-reflective and multi-directional appearance. This condition is referred to as “matte” finish. There may be slight reflectivity on materials lapped with very small micron size aluminum oxide abrasive. This is especially true if the material is relatively hard and the surface roughness measurement is perhaps 5 (.127 micron) micro-inch and below.

Very light “micro-scratches” may be viewed on lapped surfaces. Abrasive of larger micron size and harder compound will generate more micro-scratches in addition to deeper scratches. Most micro-scratches produced with small micron aluminum oxide abrasive will be less than .000001” (.025 micron) deep and can’t usually be measured with a profilometer. Micro-scratches should not be confused with deeper scratches produced by particles of contamination or other causes.

Lapmaster's SPL (Spherical Lapping) machines have been developed to produce a Convex or Concave scratch-free, high-quality surface on spherical components. The machines can also match lap a range of mating sphere components such as hydraulic timing valves. This system is effective on most materials including ceramic, graphite, ferrous metals, alloyed metals, and Stellite coatings.

The LBVS has been developed to produce very accurate spherical surfaces on a variety of Ball Valves. A scratch free, matt high-quality surfaces is obtained on the Ball Valve and Seat. The machine match laps two Seats to the valve, achieving a perfect mechanical seal for any pressure requirement.