Rolling bearings Greater than C3. Group 5. C5. Greater than C4. Hardening. There are three typical hardening methods that may be applied to bearing components: • Through- Designation system Examples and the applicable options for SKF deep groove ball bearings are given  The above letters are also used together with the clearance classes C2, C3, 
Deep groove ball bearings - 6230 d, 150, mm. D, 270, mm. B, 45, mm. d1, ≈, 190.6, mm. D1, ≈, 227.35, mm. r1,2, min. 3, mm. Abutment dimensions. da, min. 164, mm. Da, max. 256, mm. ra, maxInternal clearance Bearing internal clearance (fig. 1) is defined as the  Sufficient internal clearance in a bearing during operation is important. Preload  Greater than C3. Group 5 Bearing data Normal, C3 Check availability of C2, C4 or C5 clearance classes. Bearings for vibratory applications: C4 Bearings for high-speed applications: C4