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A broaching machine is a metalworking tool designed to finish metal by scraping away portions of it. The machine's namesake broach is a tool with ascending teeth that cut holes, such as circles and keyholes, in metal. Most broaching machines are run on hydraulic power and are very simple, but some machines use mechanical parts for complex broaching. Machines can be either horizontal or vertical; both perform about the same tasks, but vertical machines tend to be more popular because they take up less room.
The most important part of the broaching machine is the broach itself. A broach is similar to a saw, except its teeth are usually larger and they increase in size from one side to the other. There are typically several types of teeth on one broach: those that begin the cut, those that start finishing the metal and those that complete the finishing. Broaches are used to cut holes into metal, usually internal shapes such as a circle, square, hexagon, rectangle or keyhole. They also can create external shapes, such as a whole gear, but this is uncommon.
While the broaching machine is versatile, because it can be used with many different broaches, the broach itself can only be used for one purpose. Each broach is made for a specific size and shape, and it cannot be used for any other purpose size or shape. This, and the expense of broaches, means manufacturers only create new broaches if the shape is going to be mass-produced.
The majority of broaching machines are run with simple hydraulic power. This moves the broach back and forth over the metal surface, creating the shape in a matter of seconds; a broaching machine is only made for linear broaching, not rotary broaching. If the operator has a complex need, specialized broaching machines can be made that use mechanical power and have moving parts to help create any shape the operator needs. Mechanical broachers tend to have more power, so they can cut through harder metals in less time.
There are two main types of broaching machines: vertical and horizontal. Vertical machines stand up and, thus, take up less room, while a horizontal broaching machine lies down. Both are relatively the same in terms of what broaches they can use and how the machine handles the broach, but vertical machines tend to be more popular because they use less workspace. Both broachers have an average stroke of 60 inches (1.5 meters), which is enough for most metal pieces, unless they are used for large industrial purposes.