M3 XXT, Styli straight, diamond sphere, tungsten carbide shaft
Spherical styli have the largest field of application because they have the same probing behavior in every direction. They are therefore suitable for all common measuring tasks such as measuring bores and surfaces. The larger the stylus sphere size, the larger the mechanical filter. This means that the profile of your workpiece is smoothened, which is often required in form measurement. The deviation from the ideal sphere shape is usually shown in Grade. Full diamond spheres have Grade 10 as standard because of the hexagonal structure of the diamond.
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 straight shaft is the simplest stylus design and the one with the longest usable length. The full shaft length can be used as measuring length. Tungsten carbide shafts represent a good combination in terms of weight, rigidity and thermal expansion.
Diamond styli are characterized by their long durability. They are extremely resistant to material deposits and removal. They are, therefore, the ideal tool to use for measuring hard surfaces such as ceramics or for continous measuring on sharp edges. Diamond styli are recommended to be used especially when mostly one segment of the sphere is used while scanning e.g. surfaces. Several institutions such as the German PTB recommend diamond sytli for form measurements with the rotary table.