Straightedge

Straight edges and angles are hair test equipment and teachings of metalworking from hardened steel. They are used for checking surfaces for flatness ( flatness ) and straightness.

The shape is basically a straight ruler ( straightedge ) or a right angle each with a defined measuring edge. The measuring edge is in the cross section is not flat, but as a cutting edge honed sharp pointed, finely lapped and non-glare matte or burnished to avoid reflections. To maintain the shape accuracy even under bad conditions, the measured edge is provided with a small radius.

Is checked for the light splitting method, wherein the instrument with the measuring edge is mounted on the surface to be tested. The measuring edge is like a " hair " in or on the test piece. Against the light can be seen at the light gap, whether the surface is even or uneven. With good lighting deviations from 0.002 mm can be seen.