Editing Feeler gauge

{{Short description|Tool used to measure gap widths}}
[[File:Thickness gauge.jpg|thumb|right|Feeler gauge set (25 pieces, 0.03~1.0&nbsp;mm measurement range)]]
[[Image:XK engine inlet camshaft measuring valve clearance-0796.jpg|thumb|Measuring the [[Four-stroke_engine#Valve_clearance|valve clearance]] of a [[DOHC]] engine, between [[camshaft]] and [[tappet]] (here: 0.004&nbsp;[[inch|in]] ≈ 0.10&nbsp;[[millimeter|mm]]).]]

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.<ref>{{cite book|last=Webster|first=Jay |title=Outdoor Power Equipment|edition=Illustrated|year=2000|publisher=Cengage Learning|isbn=978-0-7668-1391-5|page=40|chapter=3}}</ref>

==Description==
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 unit]]s (typically measured in [[Thou (length)|thousandths of an inch]]), and one for [[Metric system|metric]] (typically measured in hundredths of a [[millimetre]]) measurements (with intervals of thousandths of an inch and hundredths of a millimetre being roughly in the same order of magnitude).

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.<ref>{{cite book|title=Today's Technician: Automotive Engine Performance|first=Douglas|last=Vidler|first2=Don|last2=Knowles|page=36|isbn=978-0-7668-4864-1|edition=3rd, illustrated|publisher=Cengage Learning|year=2003}}</ref>

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

Stainless steel is a common material for feeler gauges. Some feeler gauge sets have a single blade of brass due to the historical reason that early electronic ignition systems required the air gap between the reluctor and the pickup part being set with a non-ferrous metal.{{cn|date=February 2024}}

==Types==

===Taper===
[[Image:feelers.svg|thumb|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==
*[[Plastigauge]]

==References==
{{commons category|Feeler gauges}}

{{reflist}}

{{Measuring and alignment tools}}
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[[Category:Length, distance, or range measuring devices]]
[[Category:Metalworking measuring instruments]]