M5, Star styli, ruby sphere, stepped, tungsten carbide shaft

Star styli consist of spherical styli combined in a star shape and enable measurements in different coordinate directions. Where as probing with spherical styli from the side surfaces is only possible to a limited extent, with the star stylus you can select the stylus for probing that is orthogonal to the probed surface.

Tungsten carbide is the most common shaft material, it combines a very good stiffness with an acceptable thermal expansion. Only the weight can have a negative effect when using large styli. The design of the stepped shaft has the advantage of a greater shaft thickness, which is reduced towards the probe element. This graduation increases the stability of the stylus while maintaining the same length. However, the usable measuring length is reduced as a result. Tungsten carbide shafts represent a good combination in terms of weight, rigidity and thermal expansion.

Ruby styli are the standard for almost all applications and are available in a variety of different diameters. Another advantage is that ruby spheres can be produced in very small diameters (from 0.12 mm). On the other hand, ruby has weaknesses at the continuous scanning of certain materials and surfaces. With extremely soft materials, e.g. aluminum, material from the workpiece can be deposited on the ruby surface (material deposit). Very hard and rough surfaces, e.g. castings, on the other hand, cause abrasion of the sphere (material removal). The shape of the sphere changes as a result and loses accuracy.