In the field of engineering (mechanical), a key is an element of the machine that connects a rotating element to a nearby shaft. The key, therefore, prevents the relative rotation between these two parts and may allow torque transfer. For a key to work, the shaft and the rotating member of the machine must have a keyseat and a keyway, which are a slot and a pocket in which the key can fit into. The entire system is known as a keyed shaft or joint hinge. Keyed shafts allow relative axial movements between the parts involved.
The most common key components are pulleys, gears, clutches, and washers.
How are keyed shafts cut? Find below the process involved in keyed shaft cutting.
Keyseating (for big and special keyways)
This is done by cutting the keyway with a key-operated device which removes the material through a series of tooth-cutting movements. Some keys have only one cutting tool, while other machines (such as the Davis Keyseater) use a multi-cutter to make cutting speeds as fast as broaching.
Here’s how it works, The Keyseater cutter moves slowly outward at every cut. This subtle movement makes it possible for every stroke to remove a little more material. This process is then repeated until there is a cut deep enough to satisfy the specifications required for its application.
The main advantage of Keyseating is in the fact that it offers maximum flexibility for largely specialized keyways. The custom tooth cutters are quite easy to get and can even be quickly adapted to the specific requirements even when you’re on an onsite tool room. Depending on the type of machine, however, and the cutting tool, the Keyseating may need a longer cycle time than conventional broaching.
Shaping –for the blind keyways.
Shaping is a nice option for the cutting of blind keyed shafts. Blind in this context refers to the keyways which are not required to go the all the entire length of the way or part. Some of the keyed shaft cutting process, such as the EDM and the broaching is not designed for blind keyways handling.
Like it is with some keyseaters, this shaping uses only a single tooth as its cutting tool. But unlike others, shaping is not required to be guided down through the cuts on a fixed post. Consequent of this, the shaper cuts cannot reach the same height of accuracy as the keyseater cuts because of the unguided deflection. Therefore, this heightens the need for a proper tolerance inspection.
To cut blind keyways, usually, shapers require that users cut a “relief” at the end of the keyway that is soon to be cut. The relief makes it possible to break the fragments of the metal. You can form them by pre-drilling a hole or cutting an internal groove right inside the inner diameter
Milling (this is for shaft only keyways)
As for milling, like shaping, users are allowed to cut partial length, straight keyways or tapered. Milling is well known for the ability to cut external keyed shafts or keyways. But then, milling inside a diameter keyway on hubs is not common, the reason for this that the other side of the coupling always gets in the way. However, if it is needed, an internal hub keyway may be milled using a special 90degree singular milling head.
As with shaping, quality is a very important factor to take into account when milling keyed shafts, because of the lack of unguided cuts. Tolerances, like the corner radius quality, require special attention to ensure correct formation in line with the desired specification. Otherwise, problems may arise, for example, a key that does not match or an imbalance in the power transmission system.
Wire EDM (for small special runs)
Keyed shaft cutting with wire electric discharge machining (i.e EDM) is typically used for small quantities parts which require precision or some other specific cutting options. The tool and die manufacturers use EDM wire to remove materials through a process that may be called “shock” or “evaporation”. With this process, a coiled copper wire is brought to cut the target using electric sparks, without however directly touching the component.
We hope that this guide has given you an insight into keyed shaft cutting. If you need a way to reduce cycle time or want to cut keyways or shafts, want to reduce manufacturing costs, then contact us via phone or email. We’d guide you on which option is best for you.