There is a definite difference between a push broach and a pull broach, and this stands to reason since they carry out different functions.
Push broaches are to carry out simple arbor presses in relatively low-volume projects. If it happens that a production run is more on the medium to high volume side, you might use a push broach in conjunction with some kind of broaching machine and they have to be relatively short since they are columns in compression and would break or at least buckle under a load that was excessively heavy.
Pull broaches will always be pulled by a machine downward across a workpiece or in a horizontal direction. Manufacturers rigidly mount flat broaches so they can guide easily whatever workpiece they’re operating over the broaching teeth. This is especially true when operating on automobile cylinder blocks.
Internal broaches can be either pushed or pulled through a starter hole, and the machine can either have multi-station verticals to carry out simple processes, or it can be completely automated.
Pull-type Broaching Tools
A pull-type broaching tool is generally fairly long because the tension it creates during the pulling will build up to make it more effective. You can generally count on pull-type broaches having a longer effective life than push-type broaches. These kinds of broaches will have a great many teeth and will provide a longer cut than other types of broaches.
The pull end of a pull-type broach tool is the handle that connects to the broach tool when pulling, and the neck is that component that connects the pull end to its root diameter. The shank is an important component that extends from the pull end to the root diameter and then inside the machine. The length of a broaching tool from its pull end to its root diameter is roughly the shank length.
There are several types of teeth on a pull-type broach tool, and they are placed in the tool after the shank. The teeth size will always increase progressively from the beginning of the tool to its end, and they are divided into three different sections on the tool.
Types of Teeth
The cutting teeth are those which are nearest the shank, and they are also known as roughing teeth. There can be a big variance between consecutive teeth, but the cutting teeth will always provide the maximum cut for any workpiece, and they will remove the most amount of material from the workpiece, compared with other sections of teeth.
The semi-finishing teeth are those which are directly after the cutting teeth, and the difference in sizes between semi-finishing teeth is always less than the size difference in cutting teeth. As you might expect, semi-finishing teeth remove much less material from the workpiece while semi-finishing than the cutting teeth will.
Finishing teeth are the last section of teeth, and they always follow the semi-finishing teeth. There is no variation in the sizes of finishing teeth, and you can expect them to all be almost identical in size. These teeth accomplish the finishing to the cut after the workpiece has gone through the cutting teeth and the semi-finishing teeth.
Once the piece has gone through the finishing teeth, the rear pilot will be used to balance the broaching tool and make sure that it stays in alignment. At the very end of a pull-type brooch tool, you’ll find the follower and end retriever, which are both elements that support the tool and make it more efficient.
Push-type Broaching Tools
A push-type broaching tool is much shorter in length than a pull-type broaching tool because it goes through highly compressive forces during the time it is being pushed against a workpiece. It has far fewer teeth than any pull-type broaching tool will have, because there is a much greater likelihood of those teeth being bent or becoming broken, due to the high compressive forces which are being applied.
For that reason, it will always produce a much shorter cut than any pull-type brooch will. The parts which make up a push-type broach tool are similar to the parts you’ll find on a pull-type broach tool, but the size of the teeth, as well as other components of the broach tool, will be smaller than what you would find on a pull-type broach.
When using a push-type broaching tool, you will be able to do external broaching, in which material is removed directly from the surface of a workpiece. For this reason, it is known as “surface broaching”, and it has the specific purpose of removing material from the surface of the tool. It’s also generally used whenever it is necessary to accomplish keyway cutting or to create a slot.
How external broaches work
The teeth on an external broach tool will increase progressively down the length of the tool. On external broaches, the land acts as a support for the cutting edge and is always present at the bottom of the teeth. The rake is present in every tooth on an external broach, and you will find that the chip from a workpiece will always flow through the rake.
The clearance angle is the angle on the bottom part of the tool where the horizontal axis is. It eliminates tooth friction with the workpiece because only the cutting edge of the teeth actually comes in contact with the workpiece during the cutting process. The depth is the height of the teeth on a broach, and the pitch is the distance between cutting edges on any two teeth. The gullet radius is the space present between two teeth where the chip flows through. It generally gets directed externally after being curled.
Either push broach and a pull broach are considerably different in their operation and in their appearance, but both serve very valuable functions in the area of machining, and there are a number of different types of both these categories. Both can help to make precise cuts to prepare materials for usage in end products.
