What is the purpose of a feeler gauge?

• A. To measure weight
• B. To measure temperature
• C. To measure torque
• D. To measure clearance or gap between mating surfaces

Answer: (D)

A feeler gauge is used to determine the clearance between two mating surfaces by measuring how thick a gap is. It’s a set of blades with precisely known thicknesses; you slide blades between the surfaces and find the blade that fits with a light drag. The thickness of that blade gives you the exact gap size, typically in thousandths of an inch or hundredths of a millimeter, so you can verify or adjust to the specified tolerance. This tool is essential for ensuring parts like valve gaps, bearing clearances, or other closely spaced interfaces are not too tight or too loose. It’s not used for weight, temperature, or torque measurements, which are measured with other instruments.