Rectangular keys, as shown, are wider than their height and are sometimes called flat keys. Rectangular/square keys Rectangular shaft key (Simmons & Maguire, 2004, Google images) Not along the centre line through the shaft. Sunk keys are sunk into the shaft for half its thickness, where the measurement is taken at the side of the key. The calculations should be based on one and a half-parallel key. This should only be considered if the material is ductile. Of the above types of keys, the Parallel square key and woodruff key are probably used more widely than others due to ease of use and cost.ĭouble key – Because of manufacturing tolerances and to avoid double fits, only one parallel key is used, but Double keys are occasionally used for very high infrequent loads. Feather key (sliding clearance with keys).Shaft keys come in a wide variety of types and shapes and can be divided into four categories and subcategories. To transmit axial force, it needs a stop lock.Difficult to calculate and combine the load-carrying and the tolerance stack analysis hence keyed joints are over-dimensioned. Keyways introduce stress points due to the notch effect and reduce shaft strength.Over time keyed joints might become very difficult to dismantle.Possible axial displacement of hub unless locked by an extra component such as a set screw or retainer rings.Not suitable for alternating directional loads and shocks.Easy mount and dismount, hence easily reusableĭisadvantages of shaft keys & keyed joint.Well-standardised ( ISO, BS, DIN and ANSI).There are various advantages, and disadvantages of using shaft keys hence proper consideration must be given to the finer details of the overall design to evaluate the suitability of the keyed joint. If the set screws or, in some cases keyed joints are to be used, there must be a method of axial constraints such as circlips and retaining rings. Set screws and pins can also be used if it’s a very low-power transmission. Retention elements such as Splines, flexible couplings, and tapered joints are also used. Shaft and hub keyways are often cut on key seating machines but can also be made using broaching, milling, shaping, and slotting EDM. a – Keyway, b – key, c – keyseat, d – keyed joint (Simmons & Maguire, 2004) Generally, the term keyseat is rarely used as keyway is referred to both recesses in the industry. Keyseat is a recess in the shaft, and the Keyway is the recess in the hub to receive the key and thus securely lock the component. Shaft keys_keyway examplesĪ key is usually made from steel and is inserted or mounted between the shaft and the hub of the component in an axial direction to prevent relative movement. Keyed joints are an important part of mechanical power transmission elements shaft and couplings, where it ensures the connection transmits the load, power & rotation without slipping and within the accuracy requirement of the design. For example, Gear drives, Pulleys or Sprockets are connected securely using keys to the power transmitting shaft. Disadvantages of shaft keys & keyed jointĪ key and the keyway make up a Keyed joint to secure the hub and the shaft to prevent relative movement between a power transmitting shaft and an attached component.
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