"Inserts" or indexable inserts are used as the cutting edges for cutting tools such as tool holders for turning and face milling cutting for milling.

The insert geometry, tolerance, dimesions, and terminology are all based on the ISO standards. Other countries such as America (ANSI) and Japan (JIS, CIS) have their own standards but they are all based on the ISO standards.

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Square insert

The square insert has 4 cutting edges per side. If the insert is negative then it is possible to use a total of 8 corners. Thus making this style of insert very economical. The insert has a cutting edge angle of 90° so it has high cutting edge strength. However, the square insert needs a side cutting edge angle to machine and and such can not be used for machining a right angle.

Triangular

The triangular insert has 3 cutting edges per side. It has less corners than the square type, but is effective in machining right angles and for copy machining (copying). This insert has a cutting edge point angle of 60° and therefore it has less cutting edge strength when compared to a square insert.

80° Rhombic

This insert can be used for external machining and facing, and such is often used on CNC lathes. It is the most commonly used insert.

55° Rhombic

These types of inserts are often used for copy machining. The insert itself has less cutting edge strength when compared with other inserts geometries. However, it is essential for copy machining. The use of either 55° or 35° depends on the geometry of the workpiece being machined.

35° Rhombic

These types of inserts are often used for copy machining. The insert itself has less cutting edge strength when compared with other inserts geometries. However, it is essential for copy machining. The use of either 55° or 35° depends on the geometry of the workpiece being machined.

Trigon

This particular insert has 3 cutting edges per side. If the insert is negative then a total of 6 corners can be used.

The cutting edge angle is 80° and therefore offers high cutting edge strength. However due to the short cutting edge length the depth of cut is limited.

Round

The round insert offers the strongest cutting edge. Additionally, due to the large radius it provides the best surface finish. However there are a few disadvantages.

For example, due to the long cutting edge the chips developed are relatively wide and such difficult to break. Also due to the large contact area and the long cutting edge length, the load on the insert increases. This can result in vibrations when machining small or thin walled objects.

Round inserts are best suited for machining that requires high cutting edge strength, such as interrupted cuts, removing scale, and when machining cast iron as the chips do not elongate.