Feeler Gauges
A tool consisting of a series of thin metal blades of varying thicknesses used to measure small clearances and gaps.
A feeler gauge is a simple yet highly accurate measuring tool consisting of a series of thin steel blades of precise, graduated thicknesses, bound together at one end by a pin. Each blade is stamped with its thickness, typically in both thousandths of an inch and hundredths of a millimeter. It is used to measure the width of small gaps or clearances between two parts.
In automotive maintenance, feeler gauges are used for setting spark plug gaps, checking valve clearance on overhead camshaft engines, measuring piston ring end gap, and checking cylinder head warp when used in conjunction with a precision straightedge. Using feeler gauges ensures that clearances are within specification, preventing engine noises, rough running, or valve damage.
To use a feeler gauge, a blade is inserted into the gap. The correct measurement is indicated when the blade fits snugly with a slight drag or resistance. Using a blade that is too thin will slide freely, while one that is too thick will not fit. Maintaining the blades clean and lightly oiled prevents rust and ensures accuracy.