LO 5-3 Identify and describe common instruments and techniques to make linear precision measurements

Thickness—Feeler Gauges

Feeler gauges, commonly called thickness gauges , are linear measuring tools used to precisely measure the dimensions of small gaps or between two parts FIGURE 22. Feeler gauges are some of the most essential measuring tools owned by technicians. Several types are in most technicians’ toolboxes and are used for a variety of tasks, such as adjusting valve clearances, measuring piston ring gap clearances, determining geartrain backlash or turbocharger bearing clearances, or even adjusting sensor air gaps FIGURE 23.

FIGURE 05-22: Feeler gauges are available in a variety of lengths and thicknesses and may be bent at an angle.

FIGURE 05-23: Measuring a piston ring’s end gap with a feeler blade.

Feeler gauge blades are available in various lengths and may be flat or bent at an angle to enable them to be more easily used for a specific purpose. Metric and imperial measurement thicknesses are available in a stack of blades, and the thickness of each gauge is stamped into the base of the blade. A slight drag of a feeler blade indicates that the measured dimension is identical to the blade thickness. A spring scale can be hooked to the blade, in some circumstances, to verify whether the amount of drag is correct, since the perception of the correct amount of blade drag, or “feel,” can vary between technicians. Thickness blades may need to be put together to measure a large or unusual gap dimension. To understand the use of a set of thickness gauges, a common application is described in SKILL DRILL 5-1.