Broaching Operation

Broaching is performed using a multiple-teeth cutting tool by moving the device linearly about the work in the direction of the tool axis, as in Figure 1. The machine tool is called a broaching machine and the cutting tool is called a broach.

In some jobs for which broaching can be used, it is a highly productive method of the machining process. Advantages of the broaching process include good surface finish, close tolerances and a variety of work shapes. Owing to the complicated and often custom shaped geometry of the broach, tooling is expensive.

Broaching operation

Figure 1: Broaching operation

There are two principal types of broaching:

  1. External (surface broaching) and
  2. internal.

External broaching is performed on the outside surface of the workpiece to create a particular cross-sectional shape on the surface. Figure 2.1 shows some possible cross sections that can be formed by external broaching.

Internal broaching is accomplished on the internal surface of a hole in the part. A starting hole must be present in the part so as to insert the broach at the beginning of the broaching stroke. Figure 2.2 indicates some of the possible shapes that can be produced by internal broaching.

External and internal broaching

Figure 2: Work shapes that can be cut by (2.1) external broaching, and (2.2) internal broaching.

Cross-hatching in the above figure 2.1 and 2.2 indicates the surfaces broached.

The basic function of a broaching machine is to provide a precise linear motion of the tool past a stationary work position, but there are various ways in which this can be done.Most broaching machines can be classified as either vertical or horizontal machine.

Most broaching machines can be classified as either vertical or horizontal machine. The vertical broaching machine is designed to move the broach along a vertical path, while the horizontal broaching machine has a horizontal tool trajectory.

Most broaching machines pull the broach past the work. However, there are exceptions to this pull action. One exception is a relatively simple type called a broaching press, used only for internal broaching, that pushes the tool through the workpart. Another exception is the continuous broaching machine, in which the workparts are fixtured to an endless belt loop and moved past a stationary broach. Because of its continuous operation, this machine can be used only for surface broaching.

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