Shafts are mechanical elements that are essential for the transmission of force or power, used mainly to transmit rotational movement and torque from a point to another point. Other mechanical components, such as gears, sprockets, cams, etc. are all mounted on the shaft where required. One of the most important methods of mounting which connects such mechanical elements is the use of keys.
A keyed shaft requires a key seat on the shaft and the mechanical element too.
A key is used to transmit torque and is shaped based on the type of key it is. It is a small element which is used to transmit torque and rotary motion, in some cases, it tends to behave like a fuse because it destroys itself before the shaft or mechanical element is completely damaged.
We sell various types of keyed shafts, and we have listed and briefly described them below.
Parallel keys are otherwise called the straight keys and they are made of square and rectangular styles. These are the most used keys. As a general rule, the shaft has a slot that runs it full length which is to hold the key or alternatively, a slot that’s longer than the key which starts at the end of the shaft. During installation, the key slots on the shaft and component are aligned, and then the parallel key is pressed in.
While shaft keys come in several styles and types, the parallel keys remain the most used and common.
The rectangular keys are sometimes called the flat keys and are all-purpose components. The shafts are around 1.0 to 20in diameter. Its width is made to exceed the height so it is able to transmit more torque but does not add slot depth to the shaft and does not add keyway depth to the component key. These shafts are more than 11 inches diameters and use rectangular keys, they are mostly milled flat over their length, rather than working with as a key slot. The assembled component makes use of a standard broached-keyway.
Parallel keys are cheaper than others, they’re readily available and are easy to install. The key slot on the shaft may be cut using an end mill or with a circular saw. After installation, a screw or any other retainer accessory must be used to retain the parallel key in the position upon its mounted component. A drive in the reverse direction or a vibrating drive often causes the screw to loosen. When this happens, the parallel keys are likely to move out of the assembly.
The saddle keys are keys that are usually connected to the drive element (for example, shafts). These keys are known to have less strength than for instance, sunk keys. These keys are used to transmit less energy to the driven elements, through the couplings.
The high torque and heavy duty machines use the Tangent keys. The keyway resembles that of a parallel key, except that it tangentially extends from the outer shaft into the inner shaft. What would have been the side of each keyway is the heel against which the key is located and transmits the compressive force. This last point indicates that for a reversible motion of the shaft, another key is needed along with a tangent outward in the opposite direction. Generally, this is compensated by 90 ° or 180 ° on the shaft. The key may be wedge-shaped, square or even rectangular, but in particular the rectangular and double taper keys are mostly used.
The Woodruff keys are usually semicircular and are partially fitted into round segment keyways, the remainder is fitted to a longitudinal slot mating part. Without any reliefs, the circular segment may be cut directly with a plunge cutting using a circular woodruff cutter. The primary advantage of the Woodruff key is that there is no need for milling near the edges of the shaft, where there would be a compromise in the concentration of the tension, so no concentricity would be compromised.
The latter is majorly necessary for the high-speed operations. The tighter fit of the key and keyway reduces the space and tension concentration and improves the keys reliability. A further advantage is that when there is a stuck key, it can be removed from the shaft by a hammer blow. The circular profile pushes the key out from the slot, unlike a standard key that must be pushed axially or removed from the slot. The common applications of this are in machine tools, snow blowers, automotive applications, etc.