Slide calipers

There is a disadvantage of using ordinary calipers, namely, they do not give a direct reading of a caliper setting. Therefore, you must measure a caliper setting with a rule. Slide calipers can overcome this disadvantage.
We can use slide calipers to measure outside, inside, and other dimensions.One side of the caliper is used as a measuring rule, while the scale on the opposite side is used in measuring outside and inside dimensions. Graduations on both scales are in inches and fractions thereof. A locking screw is incorporated to hold the slide caliper jaws in position during use. Stamped on the frame are two words, “IN�?and “OUT�? These are used in reading the scale while making inside and outside measurements, respectively.
You need to move the jaws of the caliper into firm contact with the surface of the stock when measure the outside diameter of round stock or the thickness of flat stock. Finally, read the measurement at the reference line stamped out.
Insert only the rounded tips of the caliper jaws into the hole or between the two surfaces when you measure the inside diameter of a hole or the distance between two surfaces. Then read the measurement on the reference line stamped IN.
Note that two reference lines are needed if the caliper is to measure both outside and inside dimensions and that they are separated by an amount equal to the outside dimension of the rounded tips when the caliper is closed.