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How to read a standard caliper?

Some of the old-fashioned mechanical calipers have a dial that you can read directly, but they are as expensive as a digital one and you’ll enjoy the digital caliper more. However, vernier calipers—especially those made of plastic—are quite inexpensive. These aren’t nearly as good as a professional-grade caliper, but they will often do the trick. Therefore, it is extremely important for us to read the scales correctly. The basic steps are as follows:
1. Before measuring, do make sure the caliper reads 0 when fully closed. If the reading is not 0, adjust the caliper’s jaws until you get a 0 reading. If you can’t adjust the caliper, you will have to remember to add to subtract the correct offset from your final reading.
2. Close the jaws lightly on the item which you want to measure.
3. If you are measuring something round, be sure the axis of the part is perpendicular to the caliper. Namely , make sure you are measuring the full diameter. The caliper has a fixed scale and a sliding scale . Usually , the side of the scale is marked in English units and the other in metric units. The fixed scale is marked in centimeters (or 10s of millimeters). The moving scale is marked from 0 to 9 (or sometimes 10). The nearest whole number on the fixed scale that is to the left of (or exactly on ) the moving 0 indicates the number of millimeters.
4. You can use the marks on the moving scale to read down to 0.1 millimeters. The first mark (reading from the left) that lies up exactly with a mark on the fixed scale indicates the remaining digit. You can actually read more digits from a quality caliper, but usually, 0.1 millimeters should be enough.
An ordinary caliper has jaws you can place around an object, and on the other side jaws made to fit inside an object. These secondary jaws are for measuring the inside diameter of an object. Also, a stiff bar extends from the caliper as you open it that can be used to measure depth.