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Linear Broaching & Rotary Broaching: Process Guide

What is Broaching? How does a broach work? Broaching is a subtractive manufacturing process that produces features by removing material form a part with a toothed tool known as a broach. The process is divided into two main types: linear broaching and rotary broaching. Both variants are detailed in the article below.

This process is an effective and efficient technique as it produces a feature in a single pass.

Linear Broaching – basic principle

The tool is moved linearly against the work piece surface. The linear version of the process is by far the more common of the two. The principle of this process is shown in the diagram below.

Image © 2018 EngineeringClicks

Linear Broaching – round pull broaches

Round pull broaches have a 360° profile. See the diagram below for an example.

A round pull broach Image © 2018 EngineeringClicks

Geometry limitations of linear broaching

The image below shows an assortment of tools for creating various profiles. The nature of the process (fundamentally removing material along a single axis) means that the achievable geometry is simple: a 2D extruded shape.

An assortment of tools for creating different profiles

What is the difference between internal and external broaching?

Here are a few examples of the types of geometry that can be created using internal and external broaching process. The diagrams below show common internal and external forms, but a part could easily feature a combination of both if required (external and internal forms).

Common internal forms, Image © 2018 EngineeringClicks

Common external forms,  Image © 2018 EngineeringClicks

Rotary Broaching

In rotary broaching the rotating tool is pressed into the work piece, producing an axisymmetric shape. This process variant can be performed by using a milling machine or lathe. Blind shapes are easily possible using this method, and the tooling is relatively simple. The diagram below and video give further details:

Image © 2018 EngineeringClicks

Geometry limitations of rotary broaching

The image below shows examples of internal and external geometries that can be achieved.

Common external forms Image © 2018 EngineeringClicks

Typical Applications

Rifling profile of a gun barrel created by this process

Design Considerations

Materials

Process Variations

Economic Considerations

Quality Considerations

Advantages

Disadvantages