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What are Broaches?

10/8/2012 12:55:36 PM | by Anonymous


The machining process of creating a shape in a material by cutting out the excess material is called broaching and is done using a tool called a broach. Broaches are toothed tool and broaching can either be linear or rotary, depending on the desired outcome shape. Linear broaching is more common as compared to rotary broaching and as its name would suggest, the broach in this process is run linearly over the surface of the workpiece to affect a cut. The process in rotary broaching is different as the broach is rotated while being pressed into the workpiece. An example of a rotary broach application can be in a screw machine. Be it rotary or linear, the broaches are able to perform the cut in one pass of the broach and do not require to be run through or over the material again to perform the cut, making them very much efficient. The materials that are cut using a broach are usually metal or plastic. The teeth or chisels on a broach progressively increase in size, with the smallest size being on the side that would be applied on the subject material first. This is so that as the size increases, the teeth are able to remove excess material off from the subject.


Odd shapes and circular or non-circular shapes such as splines and keyways usually make use of broaching in order to achieve the desired shape. Also, some typical work pieces on which broaching are carried on include castings, forgings, stampings and screw machine parts. Although broaches are relatively expensive, many manufacturers prefer these tools over other processes or tools due to their efficiency and high-quantity production runs. Today’s broaching tools and processes have remained mostly the same from the time it was invented and before the Industrial Revolution. This is due to the fact that broaching is very effective and the original concept and design of these processes do the job efficiently. Also, broaches are very efficient with carving out polygons such as squares, especially when a circular hole needs to be expanded into a square or other non-circular shape.


Broaches fall under the category of multiple-point cutting tools due to the fact that they have more than two cutting edges to cut materials. If a manufacturer requires a broach to be customized and manufactured according to preference, he or she could send blueprints of the design to a broach manufacturer. Otherwise, stock broaches are usually available in several different lengths and sizes. Most broaches are usually made out of top quality steel and can be found available in shapes such as squares, round, oval and keyway. Broaches are single material that does not have a support structure. Therefore when they are being utilized in a machining process, it is important that a support structure be used to hold the broach in place in order to ensure consistency in the hole or design being carved out. Supports for broaches vary depending on their application. For example, a broach horn is used to support a broach in keyway broaching.


During the cutting process, several components have to be taken into consideration and ensured that they are functioning properly in order to avoid damages to the material being cut or the broach. As mentioned earlier, broach supports are essential to hold the broach in place. Therefore broach alignment is the key, relative to the material on which it is being used upon. If the broach is not aligned properly in accordance with its support and the material on which it would be working, the cuts that the broach would perform would not be straight and it could even cause the broach to snap. Also the surface of the material being cut or the backs of the cutting broaches can be lubricated in order to ensure a smooth cutting process. Lubrication helps to reduce friction ensuring a smoother cutting process.

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