Keyed Shafts

A keyed shaft is an essential component that works with a rotating machine element to effectively transmit torque to power transmission components ( learn more about power transmission applications here). It is a slotted shaft that houses a machine key or keystock so the key protrudes upwards from the shaft. This key, usually rectangular, aligns with a corresponding keyway on the rotating element and connects the two components, making them rotate together. This mechanical connection guarantees the efficient transmission of power and torque within a machine.

Application Considerations

There are several elements to consider about your power transmission application before investing in the right shafts and keys.

Key Type and Size: Think about the type of machine key or keystock that your application requires. Both fasteners are available in many different shapes that accommodate different application needs, and you will need to evaluate if your fastener fits with the given keyway size.
Material: Evaluate whether the key and shaft material are compatible with each other. They should work together to prevent the key from failing. Huyett's keyed shafts are available in 300 series stainless steel and low or medium carbon steel, while our keystock and machine keys are available in several materials, (read more in our Keystock Material Selection Guide).
Tolerance and Fit: In order for the key, keyway, and mating component to properly align, you need to be familiar with tolerance and clearance terminology. The tolerance refers to how the actual key size matches the nominal size - it can be smaller (but not larger), larger (but not smaller), or either smaller or larger than the nominal size. What you want will depend on the type of fit you want between the key and the keyway - clearance (smaller than the keyway), interference (larger than the keyway), or transition (one or the other).
Load and Torque Requirements: It is always important to understand the load requirements of any application. For keys and keyways, this helps predict how often you will need to replace the key and if the shaft can support the key without incurring damage.

Benefits

Keyed shafts offer several benefits to the given application:

Efficient Power Transmission: Keyed shafts ensure efficient transfer of power and torque from the motor or driver to the driven components.
Prevents Slippage: The groove provides a slip-resistant housing for the key. This ensures that the key, keyway, and mating component stay connected.
Easy Assembly and Disassembly: Keyed connections allow for easy assembly and disassembly of machine components for maintenance or replacement.
Cost-Effective: Implementing keyed shafts is a cost-effective method of power transmission, as it simplifies operation and allows for easy key replacements.

What is the Difference Between Keyed and Keyless Shafts?

This is a simple differentiation - a keyed shaft features a grooved keyway down the length of part or all of the shaft, while a keyless shaft is smooth all the way around.

How to Measure a Keyed Shaft

There are four key measurements you will need to take to properly measure your shaft:

Outside Diameter: The diameter of the entire shaft, regardless of the keyway
Keyway Depth: The distance from the top of the keyway (the outside of the circle) to the bottom of the keyway groove
Length: The length of the shaft from end to end
Keyway Width: The distance between the walls of the keyway

Use these measurements to determine what size machine key or keystock is right for your application. Also, evaluate whether the shaft should be measured by inch or metric standards.