Instructions of telescoping gauge

Telescoping gauges are used to measure the inside diameters of bores. The plungers are retracted and locked with the lock screw. The gauge is then inserted into the bore. When the lock screw is loosened, the plungers extend under speing pressure. Lock the lock screw, then rock the gauge to assure it is at the largest diameter. If any corrections must be made, loosen the lock screw and repeat. With the gauge removed from the bore, the plunger distance is measuremed with an outside micrometer.