Indexable Insert

In machining work where cutting, drilling, milling or other types of operation take place, the cutting tools are necessary. The cutting tools can be referred to as the tipped tools or drill bits. Unlike the traditional cutting tools which rotate at high speed to make cuts to the work pieces, the inserts are the type of cutting tool that stay stationary during a cutting operation. When cutting with inserts, it is the work piece that turns at high speed; the insert will be advanced to the rotating work piece. Once the insert contacts the surface of the workpiece, parts are removed from the rotating workpiece. The indexable inserts are the cutting tools that can be moved or positioned during an operation.

Indexing in Machining

The indexable inserts are the cutting inserts that can be indexed. To be exact, the indexing of cutting tools refers to the motion that moves the tools into a new position. The range of an indexing operation is usually very confined. The distance between the new location and the original location of the machining tools is mostly within hundredths or even thousandths of millimeters.

In addition to moving the tools into a new location, indexing also refers to the process that exposes a new cutting edge of the inserts for cutting. In the general manufacturing and engineering industry, the indexable inserts are necessary since they make a series of cutting operations possible by changing the position and cutting edges during an operation.

Indexable Inserts

The indexable inserts come with various configurations and shapes. An insert can be round, square, rectangular, triangular, octagonal or pentagonal. Regardless of the insert shape, these cutting tools all share the identical features. The essential components of an insert include the pocket floor, the insert screw, the axial location wall, the corner relief and the radial locating wall.

Pocket floor & Locating Walls

The pocket floor is the bottom of an insert. It is against the majority of the cutting force that is directed. The axial location wall and radial location wall serve as the locating edges of an indexable insert. The radial locating wall locates the correct distance of the insert from the tool center line. The axial locating edge locates the correct distance from the end face of the tool. The insert can only be positioned correctly with the two locating walls.

Corner Relief & Insert Screw

Depending on the shape of the insert, there may be more than one corner relief on a piece of insert. The relief corner is where the debris or chips are likely to accumulate when cutting. The unwanted accumulation of chips can affect the loading of the insert. The insert screw is the component that ties the insert tightly in place during a metal cutting operation.

Insert Shapes & Properties

The indexable inserts come in various shapes for a reason. The shape of the insert gives it distinctive properties for particular cutting operations. The shape affects the vibration during cutting and the ability to turn complex contours. The strength of the insert and the ability to handle heavy cuts also has to do with the shape of the insert. If it is a square insert, the nose angle is 90 degrees; if it is a triangular insert, the nose angle is 60 degrees. A round insert does not have the nose angle.

The smaller the nose angle is, the more capable the insert is to turn complex contours. On the other hand, the larger the nose angle is, the more strength the insert is and the more capable it is to take heavy cuts. With smaller nose angles, the indexable inserts require lower spindle power to perform cutting. Generally speaking, the larger nose angles allow more strength to the inserts and they are more capable of taking heavy cutting operations as a result.


Indexable inserts can be made of several materials such as cermet, ceramics, polycrystalline cubic boron nitride (PCBN) or polycrystalline diamond (PCD). Inserts made of cermet have good flank-wear resistance and crater-wear resistance; therefore, the sharpness of the cutting edge can be easily maintained. The ceramic inserts have high abrasion resistance and thermal resistance which allow a wide range of applications.

The PCBN inserts have excellent thermal resistance and they are ideal for cutting challenging materials such as hardened steels and cast iron. The PCD inserts refer to those that are made of either natural diamond or industrial diamond. They are primarily used to machine non-ferrous materials such as aluminum due to their high wear resistance. Because PCD inserts are brittle, they are not capable of machining high hardness materials.

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