When people ask, ‘what is a feeler gauge?’, they are often asking more specifically about how they are used. Understanding how to use a feeler gauge is fairly simple. There is a technique to it, but once you have got used to the feel of the tool in various gaps, it quickly becomes quite instinctive.
The most common way of using a feeler gauge is the so-called ‘Go, No Go’ technique. This involves trying out various thicknesses of blades in a gap, starting at the lower grades and working your way up.
At some point, you will reach a shim thickness that either will not go in, or that will go in but provides too much friction and resistance to slide back and forth easily. This is the ‘No Go’ point. The gap size is then determined to be equal to the last size of feeler gauge that slid back and forth in it reasonably well.
It is also easy to learn how to read a feeler gauge set. The exact placement of the measurements and sizing grades vary from brand to brand, but for the most part, you will find either metric or imperial measurements (sometimes both) etched somewhere on the blades themselves. Feeler gauge size charts are also sometimes included on the tool’s packaging, case, or storage pouch if it comes with one.
