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Key (engineering)
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<p>In <a href="/facts/Mechanical_engineering/cbId4fye">mechanical engineering</a>, a key is a <a href="/facts/Machine_element/cV69bkb9">machine element</a> used to connect a rotating machine element to a <a href="/facts/Drive_shaft/lHnhqzzT">shaft</a>. The key prevents relative rotation between the two parts and may enable <a href="/facts/Torque/KcrcvNtV">torque</a> transmission. For a key to function, the shaft and rotating machine element must have a keyway and a keyseat, which is a slot and pocket in which the key fits. The whole system is called a keyed joint. A keyed joint may allow relative axial movement between the parts. </p><p>Commonly keyed components include <a href="/facts/Gear/9KVHRfUR">gears</a>, <a href="/facts/Pulley/Mrq15sdg">pulleys</a>, <a href="/facts/Coupling/JDHEKQYn">couplings</a>, and <a href="/facts/Washer_(hardware)/3ThpTMAA">washers</a>. </p>