A broaching machine is one that is used for machining or finishing the surface of different kinds of metal components.
It will generally consist of a work table or other fixtures which are capable of holding parts in place while a broaching tool passes over them. Some kind of drive mechanism will be required to power the broaching tool in order to achieve the desired type of finish on the metal component.
Here are some of the most commonly used terms associated with broaching machines, so that you will have a better understanding of exactly what these extremely useful tools are all about.
1. Drive mechanism
The drive mechanism of any broaching machine will always consist of an electromechanical or hydraulic powered system, which is capable of powering the broaching tool. The specific function of a drive mechanism is to either push or pull a broaching tool over the surface of any metallic component so that the desired finish can be imparted to the part. The component being operated on will be static throughout the process and is simply the object of the finishing process of the broaching tool.
2. Broaching tool
A broaching tool is one that performs cutting by using graduated cutting teeth which are fixed all in a row. Each one of these cutting teeth is capable of removing a small part of the surface of the metal being operated on. As the teeth become larger and higher, a bigger chunk of metal gets removed from the surface, and the overall task of the broaching tool gets accomplished. There are two main types of broaching tools, those being linear and rotary. Linear broaching involves running the broach against the surface of the component being cut, so as to achieve the desired finish. Rotary broaching is a rapid machining method that serves to cut shapes into a workpiece and is generally used in blind operations or through-hole operations.
The worktable in a broaching operation is some kind of a fixed table that tilts and grips the component part being operated on. The center of the broaching tool and the center of the part must be aligned using a 1° offset so that a scalloping effect can be accomplished on the surface of the metal.
4. Broaching fixtures
Broaching fixtures are used whenever it’s necessary to fix a workpiece in place so that it can be operated on by a broaching tool. The broaching fixture has the function of maintaining the broach in an exact position so that a precise finish can be obtained.
5. Component tray
In any broaching operation, the component tray will serve to recycle drained oil on any broached components back into the broaching machines. This recycling of the oil prevents waste and ensures that the broached components remain lubricated throughout the process.
The pull bridge of a broaching operation always has to be guided using bars that are chrome-plated and extremely tough. This is necessary so that movement during a broaching operation is smooth and continuous, with no jerks or exaggerated movements that would degrade the finishing process.
7. Stroke adjustments
The positioning of a stroke can be modified using two different limit switches. These limit switches are positioned at the upper and lower turnaround points of a broaching machine, and they are necessary for security purposes.
8. Broaching Safety
Whenever broaching operations are in progress, there will be two pushbuttons mounted on the front of the broaching machine, and it will be necessary to push these using both hands. This avoids the possibility of any accidents happening with the machine operator because an intentional motion is required in order to begin the machining operation.
9. Combination broach
A combination brooch is a specific type of internal brooch which is capable of cutting two or more surfaces during a single pass, for instance as a spline brooch and a round brooch.
10. Double jump broach
This type of broaching tool has cutting teeth that are stepped in pairs, and these pairs are generally at higher than normal increments. The first tooth will usually take out about half the width or circumference, and the second tooth will remove the remainder. A double jump broach is commonly used where the objective is to get under the scale through the usage of heavier cuts than normal.
11. Follow diameter
This is the part of a broaching tool that is situated in the follower support bushing and can be used as a retriever when the return stroke is in progress.
12. Finishing broach
This is a very special type of broach that will only take a very light finishing cut. It is generally used when a more precise finish is the objective, and the lighter cuts make it easier to accomplish that.
13. Gullet radius
The gullet radius amounts to the curvature of space between the teeth on a broaching tool. These are actually two different radii, the first being the face angle radius which is below the cutting edge, and the other being the radius of the backside of preceding teeth, which is sometimes referred to as the heel radius.
The hook is a specific part of the actual tooth form, and it varies with the different types of materials that are being broached. In some cases, the hook is negative, and it’s also sometimes referred to as either the face angle or the rake.
15. Increased land
Increased land is the incremental increase in the total amount of tooth land which isn’t backed off. When using this kind of technique, it is possible for a tooth to be sharpened better without any significant loss of height occurring to the tooth.
16. Continuous broaching machine
This will always be a high-production machine where the component parts being operated on and will be carried through the machine on fixtures. These fixtures will be mounted on some kind of conveyor system which moves past a whole series of broaches that remain stationary. An alternative approach would be for the parts to remain stationary and have the broaches moved across them. In either case, parts would be loaded by an operator at one end of the continuous broaching machine, and they would drop out on the other end of the machine.