Broaching for Beginners: What You Should Know

A old antique broaching machine

Broaching is a common machining process that’s used to selectively remove material from a workpiece. It differs from other machining processes by relying on a specific tool called a broach. As the broach pushes against or pulls through the surface of the workpiece, it leaves behind a hole. The primary advantage of using broaching when compared to other machining process is that it’s able to create holes in odd and unique shapes.

How Broaching Machines Work

Although it can be performed by hand, most manufacturing companies use a machine when broaching a workpiece. Typically powered via hydraulic pressure, broaching machines are used to hold and maneuver the broach — the cutting tool — as it pushes against or pulls through the workpiece. There are several types of broaching machines, however, including horizontal and vertical. Vertical broaching machines are designed to push the broach against the workpiece, whereas horizontal broaching machines are designed to pull the broach through the workpiece. Statistics show that vertical broaching machines are the most common, with horizontal broaching machines only accounting for roughly one in 10 of all broaching machines purchased and used by manufacturing companies.

Materials Suitable for Broaching

Broaching can be used to remove material from workpieces made of a variety of materials, some of which include the following:

  • Steel
  • Copper
  • Aluminum
  • Graphite
  • Composite
  • Brass
  • Bronze
  • Wood

The Origins of Broaching

Broaching was pioneered during the mid-1800s when it was used to create pulleys and gears. During the early 1900s, it was used to create barrels for firearms. Today, broaching is used to create everything from small fasteners to automotive transmission gears, airplane components and more.

Pros and Cons of Broaching

The main benefit of broaching is that it’s able to create oddly shaped holes in workpieces with extreme precision. If a circular hole is needed, an alternative machining process may be used. For hexagon and other odd shapes, though, broaching is the perfect process for the job.

On the other hand, broaching machines can be quite expensive, typically costing tens of thousands of dollars. And in addition to a broaching machine, manufacturing companies must also invest in a broach. If the process is being used to create a specific shape for a specific workpiece, a custom broach must be used. Custom broaches alone can cost several hundred dollars.

Linear vs Rotary Broaching: What’s the Difference?

Broaching processes can be classified as either linear or rotary, depending on how the broach is positioned. With linear broaching — the most common type of broaching process — the broach is applied linearly to the workpiece. With rotary broaching, the broach is rotated as it presses against the workpiece.

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