Feeler Gauge: Introduction and Types

A feeler gauge is an instrument used to measure gap widths between two flat surfaces where it is difficult to reach. It is found in the metrology section.

Feeler gauge consists of small steel lengths (leaves or blades) of different thicknesses with measurements labeled on every leaf. Leaves on it are flexible enough that some can be stacked jointly to gauge mean values even if they are all on the same hinge. Having two sets of imperial units and metric measurements is familiar, though the pictured set has the size recorded on each leaf.

Image Source: Wikimedia

A similar tool with wires of particular diameter instead of flat leaves is used to set the gap in spark plugs to the correct size; this is done by changing the gap until the leaf of the proper thickness just fits between the flat surfaces.

There are many different types of feeler gauges. Some of them are:

Image Credits: Wonkee Donkee tools

1. Go-No-Go feeler gauge: It has a thick base and a thinner tip. The thinner end can ‘go’ into the gap, while the thicker body will not ‘no go.’
2. Straight leaf feeler gauge: A straight leaf feeler gauge has consistently parallel leaves
3. Metric Feeler Gauge: It gives measurements in hundredths of a millimeter.
4. Imperial feeler gauge: It gives measurements in thousandths of an inch.
5. Tapered feeler gauge: A tapered leaf feeler gauge has leaves that thin out towards the tip.
6. Feeler strip: It works identically to feeler gauge blades. The exception is that they are not connected in a set, and either end can be used to measure. They are separate for quick and easy use.
7. Offset Gauge: In this gauge blades are bent toward the tip for easier access to most motor vehicle applications and work in restrictive areas.