A broach is a bar-shaped cutting tool that contains a series of teeth, which get progressively larger and/or differ in shape from the starting end. Each tooth removes a small amount of material as the tool moves through the work piece in a one-pass operation. Please note: Broach types correspond to specific bushings, i.e., a B-1 broach will need a B-1 collared type bushing.
Diagram of a Keyway Broach
Broaching Tips:
- Materials with hardness up to HRC 38 are best suited for broaching. Harder materials are not recommended.
- Proper tool alignment is necessary to avoid tool breakage or drifting. To avoid producing a part outside of the required tolerance, make sure at least two teeth are engaged at all times and use bushings to provide support for the broach.
- Proper lubrication reduces friction and helps with chip removal.
- Clear chips with a stiff brush from the cutting section of broach following each pass.
Types of Broaches:
Keyway broaches are used to form starter holes, remove material or shape a workpiece. These and other rotary broaches are used in a one-pass operation and have a bar-shaped design with several teeth that can progressively increase in height or shape from the starting end. A keyway broach also will produce a polished finish on an end product. Save time and increase efficiencies with keyway broaching tools. Keyway broach sets are also available.
Square broaches produce square-shaped holes while removing a small amount of material in a one-pass operation. They typically have an oversized pilot that leaves drill marks in the flats to provide relief while establishing four corners in a hole. The pilot diameter will equal the finished square size. Ideal for enlarging, shaping and finishing irregular shapes in a workpiece.
Hexagon broaches produce hexagon-shaped holes while removing a small amount of material in a one-pass operation. Ideal for enlarging, shaping and finishing irregular shapes in a workpiece.
Types of Keyways:
- Keyseating broaches are used for producing keyway-shaped holes in a workpiece. They are ground to precision keyway tolerances and designed for AF series machines.
- Keyway broaches are used for producing keyway-shaped holes in a workpiece. They may be used with shims if the depth cannot be broached in a single pass. They also require a guide bushing for producing the keyway.
- One-pass keyway broaches are used for cutting the full width and depth of the workpiece in smaller run productions. They do not require any shims or bushings.
- Production keyway broaches are designed for extended production runs of identical keyways and bores. These broaches are used for cutting the full width and depth of the workpiece in high- speed and long production runs. They are self-supporting and do not require any shims or bushings.
- Single point keyway broaches are used for blind hole and through hole operations with CNC machines. They can be sharpened several times to extend tool life.
The Round Broach:
Round broaches produce round-shaped holes and are designed with a variable pitch for greater precision. They are used in a one-pass operation.
Rotary Broaches quickly produce polygon shapes in blind holes in a one-pass operation. Ideal for automotive, aerospace and medical industries.
Broaching Operations:
Internal operations shape a round-drilled hole into any configuration. This broaching can be done with either a push or a pull broach. Most broaches are push broaches. Pull broaches (AF Stock) offer longer lengths of cut when broaching square and hexagon shapes. Examples include tooling fixtures, gear and pulley keyways, keyways, rifling and all hole configurations.
External (Surface) operations are used in place of milling or shaping operations because they can produce exact dimensions at a much faster rate. Examples include flats, notches, keyways, contoured surfaces, external gear teeth and serrations.
Broach Material and Finishes:
High Speed Steel (HSS) provides good wear resistance and can be used in general-purpose applications for both ferrous and nonferrous materials.
Bright provides a smooth, polished finish on the tool. It increases chip flow in softer materials such as aluminum, wood and plastic.
Titanium Nitride (TiN) is a multi-purpose coating that increases chip flow in softer materials. The heat and hardness-resistance allows the tool to run at higher speeds than uncoated tools.
Titanium Aluminum Nitride (TiAlN) has a high hardness and oxidation temperature. As a result, it is particularly advantageous for higher speed operations in a variety of steel machining applications.
Broach Accessories:
Broach Bushings are metal slotted liners that support and guide the broach. Available in plain or collared types. Collared bushings are for ease of use in smaller holes. Broach bushing sets for keyway broaches are also available.
Broach Shims are a thin piece of metal used to achieve a given depth of keyway in a bore.
Rotary Broaching Setup Plugs are used to make it easier for broaching a blind hole. They are used for removing the guesswork from the operation. Plugs are commonly used with rotary broaches and broach holders.
Rotary Broach Holders are used for holding a variety of broach shapes including hex and square. They are designed with an internal spindle and can be used on CNC, manual turning, milling or screw machines.