However, for the metric coding, the diameter of an inscribed circle is represented by the cutting edge length using a two-digit number. Therefore, even if the inscribed circle is the same , the symbol for the cutting edge will vary.

The symbol represents the clearance angle of the insert used. An insert with a 0° clearance angle, which is shown by the symbol N, is called a negative insert. An insert with a clearance angle other than 0° is called a positive insert. Many turning inserts have clearance angles shown by symbols N, C and P.

For example, an inscribed circle of 9.525 mm (3/8 inch) is represented by the symbol 3. An inscribed circle of 12.70 mm (4/8 inch) is shown as 4.

Geometries including triangle, square, round, polygon and rhombus are standard. All of the insert geometries are symbolized using the alphabet.

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