How to read a milling insert code
The first six positions are the same as turning inserts: shape, clearance, tolerance, type, size and thickness. Milling then adds its own: instead of the radius, or after it, many inserts carry two letters for the wiper edge, the small flat that leaves the surface smooth. The first letter is the main cutting edge angle (A 45°, E 75°, P 90°), the second the wiper clearance. Then come the edge preparation and the hand.
In SEKN 1203AFTN the letters AF mean: main cutting edge at 45° and wiper with 25° clearance. At 45° the cutter faces with thin chips and spread-out forces, but cannot mill 90° shoulders.
20° clearance: a positive insert, cutting with less force. The usual choice for shoulder mills and less powerful machines.
Similar codes
Designation to ISO 1832; reference tables: Mitsubishi Materials milling catalogue (insert identification). Chipbreaker, grade and cutting data differ between makers: the catalogue of the insert you use is what counts.