If you haven’t heard of broaching before, it consists of a machining process that uses a specific tool that has many teeth, to remove metallic material accurately and predictably. You can think of a broach as a succession of single-point tools which have been arranged in an axial direction along a holder or tool body, and each one of these teeth will vary in its shape and its size, to cut a chip out of the workpiece of a pre-specified thickness.
The shape of each broach tooth, as well as its spacing, will generally be determined by the length of the part which you intend to have broached, as well as the amount of material that must be removed by each tooth. The tonnage restrictions of whatever broaching machine is being used will also have an impact on the shape and spacing of broach teeth. The chip space between broach teeth will generally be designed to accommodate however many chips are being generated during the process.
There are two main types of broaching services, those being rotary and linear, and these processes are used to produce a wide range of different machine finishes. In either type of broaching, the aim is to achieve a precision finish for a high volume of items going through the process. As you might expect, the broaching process relies on a tool which is known as a broach. One critical factor of any broach is the rise for each tooth on the tool, and this will have a direct impact on the amount of material that can be removed by the tooth on every pass.
These teeth are arranged into sections along the body of the tool, and the sections all have specific purposes, e.g. roughing, semi-finishing, and finishing. All broaches fall into one of two categories, which are either surface brooches or internal brooches. Surface brooches take in a wide variety of different designs and are one of several types: slab, straddle, contour, pot, or slot brooches.
Internal broaches are a totally different style of broach, and these also come in several different varieties, for instance, keyway broaches, modular, solid, shallow, concentricity, or cut-and-recut. No matter which type of broach you might be using, both the internal and surface models are generally made from either high-speed steel or alloy steel. High-speed steel broaches generally have their bits coated with TIN, while alloy steel broaches do not require this kind of coating.
The Broaching Process
The broaching process used will depend on whether you’re using an internal broach or a surface broach. Probably the more straightforward operation is surface broaching since it involves having one surface acting upon another. As an example, you could have the broaching tool staying stationary with the workpiece being moved against it. Alternatively, you might have the workpiece being stationary while the broach gets moved against it.
Internal broaching is not quite as simple as surface broaching, and it calls for the workpiece to be secured in place with some type of holder, and that holder will also serve as the mount for a broaching machine. Then it will be necessary to make use of the elevator on the broaching machine to lower the broach into the workpiece. After this, a puller on the machine will grab the broach pilot, and after the elevator releases the follower, the broach will be pulled all the way through the piece.
Following this operation, the workpiece will be removed, and the broach will then re-engage with the machine elevator. This broaching process is used in many different ways and for many different applications. Broaching is often used in the production of hand tools, plumbing, appliances, farming equipment, automotive products, and a whole slew of industrial and military applications.
In general, the main usage for broaching will be in producing high-volume parts that must have cuts made on them that are accurate, complex, and very repeatable. The broaching process can be used in a tremendous variety of applications, and most of those applications call for materials which have a hardness rating between 26 and 28 Rockwell C. Many production companies have even used materials which are as hard as 32 Rockwell C, because it was necessary for their particular application.
How Broaches should be Cared for
Since it requires considerable effort to prepare a broach for working on any given application, it makes good sense to protect your investment and take good care of the broach you will be using for high-volume production. At the beginning of its life, any new broach will probably last for at least 8,000 cuts, but you can extend the lifecycle of a good broach with regular care and sharpening. In some cases, you might be able to extend that 8,000 cuts into 60,000 cuts or even more, depending on just how committed you are to maintaining it and using it properly.
Given the fact that any new broach is likely to cost upwards of $2,000, it is certainly to your advantage to take as good care of your broach as possible, so that you don’t have to purchase new ones too frequently. Many smaller companies simply can’t afford to buy new broaches as often as a large company could, and that means they have to take very good care of their broaches in between usages.
As a rule of thumb, it’s a good idea to send out your broaches to be reconditioned and sharpened after having made 3,000 cuts or so. You’ll find that it’s much easier to keep your broach in good operating condition and that it significantly extends the life of your broach so you won’t be buying new ones as often.
This will lower your overall production costs and allow you to make more of a profit on high-volume production runs. Whenever you notice that more force is required to cut your parts, that’s a good sign that your broach may be losing its edge and requires sharpening. By paying attention to the warning signs when a broach is being used in production, you can avoid costly replacement parts, and maintain greater profitability for your company.