Chamfers and fillets

The general rule is that all external corners must be chamfered and all internal corners filleted. The reasons are many and complex: safety precautions, ease assembly, aesthetics, reduce load concentration, threading, tapping, heat treating, surface coating, casting, painting, stamping, forging, and many more.
The chamfers usually made at 45 degrees, for ease assembly of shafts a smaller angle may be used ( from 15 to 30 degrees), for free non-contacting surfaces are given chamfers within 0.1 to 0.2 mm. Such chamfers are not indicated in drawings (in contrast to the design chamfers); a note merely says, “Remove sharp corners”. Often the necessity for removing sharp corners is indicated in the technical specifications pertinent to the part, the chamfer size and the tolerances being specified.

The leg   of a chamfer for usual cylindrical components is obtained from the formula:

Where,
D is the diameter of the cylinder.
The values obtained with the aid of this formula are rounded off to standard values:

 s=0.2; 0.5; 0.8; 1; 1.2; 1.5; 1.8; 2; 2.5; 3; 3.5; 4; 5.

All dimension are in millimeters.