The Model 3363 is capable of making scratch hardness measurements in accordance with ASTM D 3363. It uses constant pressure and pencil leads having various forms of hardness. These leads, having various degrees of hardness, are moved over the surface being tested under a fixed pressure and at a fixed angle to the surface. The degree of hardness of the pencil lead, which damages the surface, is taken as a measurement of scratch hardness.
The instrument consists of a pencil lead holder carried on two rollers, the weight of which is so arranged that the pressure exerted by the flat pencil lead is approximately 300 grams. A hand grip is provided for pushing the instrument over the specimen. Fourteen pencil leads, in the range of grades from 6B to 6H are used. The pencil leads can be exchanged easily.