Loeser SZ 250

In cylindrical grinding, the workpiece is held between centers or in a chuck and rotated against the grinding wheel — the workpiece center position is fixed by the fixturing. In centerless grinding, the workpiece is not fixed: it rides on a work rest blade between the grinding wheel (which removes material) and a regulating wheel (which controls rotation speed and through-feed rate). The workpiece's position is controlled by the geometry of the blade-wheel-regulating wheel relationship, not by mechanical fixturing. Centerless grinding is faster for high volumes because loading is simpler, but it cannot grind features that require a fixed datum like cylindrical grinding can.

In through-feed mode, the SZ 250 handles workpiece diameters from approximately 1 mm to 60 mm. In infeed mode, larger diameters up to approximately 80 mm are possible. The minimum diameter for through-feed is limited by the stability of small-diameter workpieces on the work rest blade — very thin parts (under 2–3 mm) require specialized blade and wheel configurations to prevent the part from riding up the wheel.

Under production conditions with properly dressed wheels, correct blade height, and appropriate regulating wheel speed, the SZ 250 can achieve roundness (out-of-roundness) of 0.001–0.003 mm (1–3 µm). For bearing-quality roller elements, roundness below 0.001 mm is achievable with optimized setup and premium CBN wheels. The achievable roundness is influenced significantly by the incoming workpiece roundness — centerless grinding cannot easily correct a strongly out-of-round starting condition in a single pass.

Yes, the SZ 250 supports CBN (cubic boron nitride) grinding wheels. CBN is commonly used in high-volume centerless grinding of hardened steel (60+ HRc) bearing components and precision pins because CBN wheels last dramatically longer than conventional abrasive wheels, maintain their profile more consistently, and can grind hardened steel faster without burning. The SZ 250's spindle speed and power specifications support vitrified-bond CBN wheels, which are the industry standard for bearing component centerless grinding.

Loeser and Mikrosa (United Grinding) are both German centerless grinding specialists, and both produce quality production centerless grinders. Mikrosa tends to focus more on the high-precision, high-volume bearing and automotive component segment with very high-rigidity machines. Loeser offers comparable capability with perhaps a slightly broader application range covering precision parts and job shop work. Both brands are well-regarded and the choice often comes down to application-specific requirements, existing machine fleet relationships, and the application engineering support provided by each company's sales team.