How to cut a key slot in a shaft
A key slot, most commonly called a key way, can be cut into a shaft by broaching, electrical discharge machining (EDM), milling, and shaping/slotting.
Broaching is a machining process that uses a cutting tool called a broach to remove material. There are two types of broaching used, linear and rotary. Linear broaching is the most common method of broaching where the broach is run linearly against the shaft creating a key way the entire length of the shaft or hub. Rotary, while less common, involves a rotating tool that is pressed into the work piece. Rotary broaching can create full length key ways as well as blind key ways.
Electrical Discharge Machining (EDM) uses an electrically charged wire to displace material. EDM is a highly accurate method of machining keyways, however due to it slower process, it is typically used for shorter runs or made-to-order applications.
The Shaping/Slotting machining process works well for machining blind key ways or external key ways that do not traverse the entire length of a shaft. Shaping or slotting is also a viable solution for machining internal key ways like those found on gears or hub assemblies.
Milling is similar to shaping as it allows a keyway to be cut the partial length of a shaft or hub, however milling uses a rotary cutter as opposed to a fixed bit. Milling is commonly used for external keyway applications rather than internal keyways due to clearance and interference conflicts from the milling machine.