How To Read a Caliper

A caliper is a measuring tool that provides a more accurate measurement than an ordinary ruler. It is commonly used in laboratories and industries engaged in metal works, engineering, wood works and medicine. 

The vernier caliper is the most common type of caliper. It is the most convenient tool to use when measuring the length of an object, the outer diameter of a round object, the inner diameter of a cylindrical object like a pipe, or the depth of a hole. It looks like a ruler except that it has jaws that are placed around or within the object. The vernier caliper can be as accurate to give up to a hundredth of a millimeter or one thousandth of an inch.

Although there are already digital calipers available in the market today, the old-fashioned ones are still used especially by small industries, as digital calipers can be very expensive. Digital calipers are obviously the most accurate ones to use but given the right knowledge of reading the manual old-fashioned calipers, the correct measurement will still be achieved.

Here are the steps that you should know in reading a caliper:

  1. Prepare the caliper. Before you do your measurement, you have to check your instrument first. Make sure that the caliper, when fully closed, reads zero. If this is not the case, you will need to adjust the jaws of your caliper. If it still doesn’t give a zero reading, you will need to remember to make additions or subtractions from your final reading to offset the discrepancy. It can be a hassle when this happens so it is best to find a caliper that does give a perfect zero reading when fully closed.
  2. Prepare the material to be measured. Place it inside the jaws of the caliper. Adjust the jaws so it closes in lightly, especially when measuring soft objects. If you are measuring cylindrical objects, make sure that you are measuring the full diameter. You can do this by seeing that the axis of the material is perpendicular to your caliper.
  3. Understand the scale. A caliper has a fixed scale and a sliding scale. You will notice that on its side, the caliper's scale is marked in English units and the other side in metric units. The caliper's fixed scale has centimeter marks while the sliding scale has marks 0 to 9. The number or millimeters is determined by the nearest whole number on the fixed scale that is on the left side of the sliding scale.
  4. Read the scale. Use the marks on the scale to be able to read up to 0.1 millimeters. The first mark from the left side that is laid exactly on the mark on the fixed scale gives you the remaining digit. 

Standard calipers can give values of up to 0.1 millimeters, only digital ones can give more accurate measures. However, the 0.1 millimeter reading of your caliper will normally suffice. As with any measuring tool, some errors may come out. Nevertheless, with constant usage, you will eventually get a good sense of feel and will achieve more accurate results.


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