A broach is a tool that is equipped with teeth that are used to remove specific materials from a larger object. The broaching process calls for a machine that manipulates the broach, using a single pass to take away unwanted material. Broaching was originally conceived of as a method to machine internal keyways, but its usage has now been expanded to include a variety of other applications and can be used to machine a number of different surfaces and shapes.
It is an excellent process for achieving finished metal products by machining shapes, and it’s particularly good at doing precision machining of non-standard shapes such as splines, keyways, and non-circular holes. Because broaching can do all this in one pass, it’s not only very efficient, but it’s a cost-saving approach, especially when implemented for applications done in high-volume.
Advantages of Broaching
There are quite a few advantages derived from the broaching process, and all of these contribute to the fact that it has become such a popular process. First of all, the rate of production is extremely high because broaching is such an efficient process, and is very repeatable. Another reason broaching is so beneficial is that it doesn’t require much skill on the part of an operator to perform an actual broaching operation. In most cases, all that’s necessary is to have the operator load and unload a given work piece, and the broaching machine will do everything else.
It’s possible to achieve a very high level of accuracy in addition to an excellent class of surface finish when using a broaching process. It’s typical to achieve a level of accuracy which has an extremely low tolerance of error, as well as a finish which is just as precise. Another advantage of broaching is that both the rough cut and the finished cut will be completed with a single pass of the machine, and this not only saves time but money as well because it’s not necessary to undergo repeated passes.
There is also a good deal of versatility associated with the broaching process because it can be used for both internal and external surface finishing. It’s also possible to apply cutting fluid when needed because a broaching machine has a tendency to pull the fluid into the cut, which assists the whole process. Since most pieces are designed around standard broach geometry, the process is extremely economical, regardless of how many pieces are being machined.
That economy is in effect whether you’re machining a single piece or 1,000 units. It’s also true that the pieces you’re working with don’t really need to be designed for standard broach geometry, because broaching can be custom-designed to accommodate almost any kind of geometry when unique shapes are required.
Broaching Methods
There are several different broaching process methods that are commonly used in business today. The first of these is known as pull broaching, in which a work piece is fixed in place and the brooch is actually pulled through it. Most often, broaches are rather long and must be held in a special head. The pull broaching method is generally used for internal broaching, but it can also be applied in instances where surface broaching is indicated.
The next method is known as push broaching, and in this situation, a work piece is fixed and the broach is pushed right through it. It’s fairly common to have hand presses and hydraulic arbor presses in use for push broaching. The most common applications for push broaching are for sizing holes and for cutting keyways.
Surface broaching is a process that calls for either the work piece or the broaching tool to be moved across the other one. In recent years, this has become a very popular and important method for achieving surface finishing. Surface broaching will be excellent at broaching a number of intricate shapes or irregular shapes, although it will be necessary to specially design the tools for each individual application.
Continuous broaching is a method in which the work piece is moved continuously while the broach remains fixed in place. The movement of the process can be either circular or along a straight horizontal. This method is mostly used for broaching a whole slew of similar work pieces all at once.
Types of Broaching Machines
There are four basic types of broaching machines, those being horizontal broaching machines, vertical machines, surface machines, and continuous broaching machines. A horizontal broaching machine almost always uses the pull broaching method, and it can be used for either internal or external broaching. This type of machine consists of a base which is twice the length of the broaching stroke, a broach pilot, and some kind of drive mechanism which is used to pull the broach. These machines are normally used to broach round holes, splines, keyways, and other shapes.
A vertical broaching machine might be used in either a pull broaching process or in push broaching, although push broaching is more popular. Vertical broaching machines can be used in a number of operations because it’s so easy to pass work along between several machines. A vertical broaching machine requires an operator platform but does not need a lot of floor space, so it’s good in tight areas.
A surface broaching machine has its broaching tools fixed to a ram, which is forced in a straight path using guideways to push it past a given work piece. Some surface broaching machines have rams that move horizontally, while others have their rams moving vertically. In some cases, two rams are employed, and these are called duplex brooch machines.
A continuous broaching machine is used most often for the mass production of smaller work pieces, and it’s a highly productive process because it uses either horizontal or rotary broaching equipment. When rotary continuous broaching machines are used, a work piece would be loaded on a table which is continuously rotating, while the broach itself remains fixed.
Horizontal continuous broaching machines call for the work pieces to move as they are carried along by a tracked chain. The work pieces are then fed into holding fixtures that are mounted atop the constantly moving chain. While in operation, the broach remains fixed in place to accomplish the broaching process. Continuous broaching machines are most commonly used to accomplish the broaching of small parts.
