Feeler gauge

A feeler gauge is a tool used to measure gap widths. Feeler gauges are mostly used in engineering to measure the clearance between two parts.[1]

Feeler gauge set
Measuring the valve clearance of a DOHC engine, between camshaft and tappet (here: 0.004 inch ≈ 0,102 mm).


They consist of a number of small lengths of steel of different thicknesses with measurements marked on each piece. They are flexible enough that, even if they are all on the same hinge, several can be stacked together to gauge intermediate values. It is common to have two sets: one for imperial units (typically measured in thousandths of an inch), and one for metric (typically measured in hundredths of a millimetre) measurements.

The same device with wires of specific diameter instead of flat blades is used to set the gap in spark plugs to the correct size; this is done by increasing or decreasing the gap until the gauge of the correct size just fits inside the gap.[2]

The lengths of steel are sometimes called leaves or blades, although they have no sharp edge.



Tapered (upper) and parallel (lower) feeler gauges

A taper feeler gauge is a feeler gauge of tapered, as opposed to parallel, shape. The blade of the gauge is of a constant thickness, and the two types of gauge are used in a similar way.

See also


  1. Webster, Jay (2000). "3". Outdoor Power Equipment (Illustrated ed.). Cengage Learning. p. 40. ISBN 978-0-7668-1391-5.
  2. Vidler, Douglas; Knowles, Don (2003). Today's Technician: Automotive Engine Performance (3rd, illustrated ed.). Cengage Learning. p. 36. ISBN 978-0-7668-4864-1.
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