Inside & Outside Calipers & Scribers

Inside & Outside Calipers

Calipers are a type of measuring device typically used to measure diameters and distances or for comparing sizes. As an aviation maintenance technician you must be familiar with three types of calipers. They are the inside caliper, the outside caliper, and the hermaphrodite caliper. Calipers are very similar to dividers in that they have two legs with some type of pivot. Inside calipers are used to measure the inside diameter of a hole, and have legs that point outward. Outside calipers, on the other hand, are used to measure the outside diameter of an object and have legs that point inward. When using either type of calipers you adjust the caliper until it fits snugly across the widest part of an object, and then measure the distance between the caliper leg points with a steel scale.

Scribers

Dimension layout on metal parts, regardless of the accuracy, is typically accomplished by using layout dye and a marking tool called a scriber. Scriber have needle-sharp points and are usually made of hard steel or are carbide tipped. To use a scriber, a layout dye is typically applied to the metal first and the scriber is used to scratch through the dye. However, this procedure will causes stress concentrations on the surface of a bend and, therefore, it is not acceptable to use this method to indicate bend lines. Instead bend lines should be marked with a soft tipped marker.