Broaching is a process that has been around for about 100 years, and it is so useful and so valuable, that it appears poised to be in use for another century or so. It makes use of a tool called a broach which consists of a cutting tool that has many different rows of teeth, each of which is slightly larger than the last one. In a broaching operation, as the broach moves past a work piece, or a work piece is forced over a broach, each one of the teeth takes a shallow cut along the entire length of the work piece, and carries the chip that it cut right to the end.
Broaches are designed to produce either simple forms or complex forms in a short period of time, commonly in one pass, with accuracy that is extremely reliable and repeatable. In general, a broach will consist of several rows of teeth that do the rough cutwork, then several more rows that do semi-finishing, and another few rows which accomplish the actual finish on the surface.
Each broaching tool is designed for the shape which is being cut and takes into account the properties of the work piece along with several other factors. Almost any shape imaginable can be broached internally or externally, producing everything from simple slots and flats to turbine blade hubs for huge engines used by aircraft. Broaching is quite often used for the purpose of cutting precise diameters or producing holes that are non-circular such as a square, a hex, or a double-D shape.
A broaching operation can be used to cut gear teeth and splines because all the dimensions necessary can be built into the same tool. Because it is so efficient and so repeatable, broaching can lower the cost of machining shapes down to mere pennies for each work piece. It is also capable of performing cuts which would be virtually impossible to achieve using any other method. Machines used for broaching are available in several different configurations and can be used for either surface broaching, internal broaching, or external broaching.
Applications for the Broaching Operation
Just about anything which can be cut by a machine process can make use of a broaching operation effectively and economically, and the output of the broaching process is used in farm implements, automotive industry hand tools, plumbing, appliances, turbines, and even military applications. When a broaching tool is being designed, the properties of the work piece are taken into account, and the design will include features that are ideal for the cutting speed it will be operated at, in order to achieve the best results on any specific work piece.
Cost of Broaching Machines
While the cost of the broaching operation itself is extremely economical, it does call for capital investment to create the machines which will be used for the broaching process. This is particularly true if you’re investing in a high-volume machine which is intended to mass-produce work pieces. The good news about these types of machines, however, is that when you get into a mass production environment, there is a tremendous economy achieved by running so many units through the machine.
The first step in the process is to design a broach which would be used to machine a given work piece, and then design the machine to accommodate the broach. There are a number of different types of broaching machines which can be used, and these can be modified to make them bigger or smaller, using more or less pressure, and to operate at various speeds.
In effect, this makes all broaching machines different in some way, so that most of them are custom-built to a client’s order. It’s very much like purchasing an automobile, in that you have a base price for the whole vehicle, but then there are options added on which raise the sticker price significantly above that base. While some customers do opt for the bare-bones version of a broaching machine, others are aware that adding those extra options will achieve cost savings in the long run, and therefore opt to have them included on the machine.
Caring for a Broaching Machine
It’s a good idea when bringing a new broaching machine into your company for whatever broaching operation you need, that you take some time to train your staff on how to use the new machine because it will save a lot of time and money. When machines are not used properly, they can quickly wear down, and that will result in a shorter life cycle and a much greater expense either for repairs or replacement.
It’s fairly well known in the industry that taking good care of broaches both while they’re in use and while they are being stored is very important to maintaining a profitable business. For instance, if you have a new $3,000 broach and you run it until it fails, you might be obliged to discard it at that point and that is the limit of the value which you derive from it.
However, if you run the tool for a period of time and then sharpen it, you will get much more life out of it and it will last a lot longer so you can get more work pieces from it. The sharpening process itself costs less than $100, so it’s well worth it to extend the life of a broaching tool which costs thousands of dollars.
When a broaching tool is not in use, it needs to be stored carefully so that the cutting edges don’t sustain any damage. While it’s a somewhat common practice to leave broaches laying around on the bench, this is not good at all for the life of the broach. Instead, they should be stored in containers made of plastic, wood, or cardboard, so that the teeth can dig in but won’t be damaged. You can have your broaching tool sharpened at a shop that specializes in that process, but you will save more money by purchasing a sharpening machine and doing it at your own shop.