Allowable clearance in mechanics refers to the maximum acceptable amount of space or gap allowed between two interacting mechanical parts, such as bearings or gears. This clearance is typically specified in the design of the parts and is critical for proper functioning and long-term durability. The allowable clearance must take into account factors such as material properties, lubrication, temperature changes, and expected loads and stresses. If the clearance is too small, the parts may bind or seize, causing damage and failure. If the clearance is too large, the parts may rattle or vibrate excessively, leading to wear and premature failure.