A parallel machine key is a rectangular metal component fitted into matching keyways on a shaft and hub. It creates a mechanical connection between the two parts, allowing torque to be transmitted while preventing relative rotation.
Unlike tapered keys, parallel keys have a consistent width and height along their length. Their flat faces and parallel sides provide contact with the corresponding keyway surfaces.
Key design features include:
- Rectangular cross-section: Provides the working surfaces for torque transmission.
- Parallel sides: Maintain consistent dimensions along the key length.
- Flat faces: Fit into the shaft and hub keyways.
- Different end shapes: Available with square, rounded, or other end profiles depending on installation requirements.
Parallel machine keys primarily prevent rotational movement rather than axial movement. If the assembly requires axial positioning or retention, additional securing features may be needed.
How Parallel Keys Transfer Torque Between a Shaft and Hub
A parallel key transfers torque through direct contact with the shaft and hub keyways.
During installation, the key seats in the shaft keyway, and the hub is fitted over it so the two keyways align. Once assembled, the key engages both components, allowing the shaft and hub to rotate together.
Several dimensions affect the fit and performance of the connection:
- Key width: Must match the shaft and hub keyways to provide proper side-face engagement without excessive clearance.
- Key height: Determines how the key sits within the shaft keyway and engages with the hub keyway.
- Key length: Influences the available contact area and should suit the shaft diameter, hub geometry, and torque requirements.
- Side-face condition: Burrs, uneven surfaces, or dimensional variations can affect contact between the key and keyways.
Where Custom Parallel Machine Keys Are Used
Custom parallel machine keys are commonly used in mechanical assemblies where rotational power needs to be transferred between a shaft and a mounted component.
Electric Motors and Drive Assemblies
Gearboxes and Transmission Systems
Pumps and Industrial Machinery
Conveyor and Material Handling Equipment
Machine Tools and Mechanical Fixtures
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Frequently Asked Questions
What is the difference between a parallel key and a tapered key?
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The main difference is their shape and how they fit into the keyway. A parallel key has a consistent rectangular cross-section, while a tapered key gradually changes in thickness to create a wedge fit. The choice depends on the shaft and hub design and the required assembly method.
Are parallel machine keys used for torque transmission?
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Yes. Parallel keys are widely used to connect shafts with gears, pulleys, sprockets, and couplings. They transmit torque through contact between the key and the side walls of the mating keyways. The correct dimensions and material are important for reliable operation under the intended load.
Can KEY-CNC make parallel keys to custom specifications?
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Yes. KEY-CNC can review custom parallel key requirements using engineering drawings, samples, or specified dimensions. Whether you need a non-standard size or a replacement component, our team can assess the design and machining requirements before production.
What details should I provide when requesting a quote?
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Please include the key's width, height, length, material, required tolerances, and order quantity. If the key has special end shapes or other design features, include those details as well. A 2D drawing or STEP file is particularly helpful for checking dimensions and preparing an accurate quotation.
Do you accept prototype and small-batch orders?
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Yes. We support prototype development, small-batch orders, and production quantities. The suitable manufacturing approach can be discussed after reviewing the part design, material, and required quantity.
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