 Welcome to this activity on the dial caliper. Calipers are basic measuring tools for most machinists. Not only are calipers easy and fast to use, they are also versatile, measuring inside and outside dimensions and depth. When should you use a caliper, and when should you use a micrometer? People often assume that because the caliper reads to a thousandth of an inch, it's accurate for tolerances of plus or minus one thousandth of an inch. However, experience has shown that the dial caliper is not reliable for tolerances less than plus or minus five thousandths of an inch. Misalignment errors often occur when people measure at the bottom of the jaws because this line of measurement is so far away from the scale standard. These errors can be misalignment of the caliper on the part or misalignment due to play in the jaw. To minimize these errors, measure as close to the beam as possible. It's particularly easy to misalign the caliper in depth and step measurements. Hold the caliper squarely against the top surface and firmly against the front of the part. Check the zero setting frequently. Clean the jaws and the part before taking a measurement. Overtightening springs the jaws. Check for this by holding the closed jaws up to the light. Avoid dropping your calipers even once. Frequently check the jaws for burrs. Don't hold your calipers too long. Holding a 24-inch caliper with two hands for just five minutes will expand it by one thousandth of an inch. The internal jaws may measure a hole smaller than it actually is because they're offset and also because the flat caliper jaw is trying to measure around diameter. The smaller the diameter, the greater the error. Keep your calipers away from oil and chips. Chips that get stuck in the caliper rack can be difficult to remove. Store your calipers horizontally in a case with the jaws slightly open. The metal-to-metal contact of closed jaws can corrode them. You have completed this activity, the dial caliper.