Mitutoyo calipers are precision measuring devices that need to be calibrated once in a while to give the user an accurate measurement. By cleaning them of any debris, you can assure that they can be calibrated correctly. Simply using precision gauge blocks to check their accuracy every day can also let you know when it is time to recalibrate them to assure that your parts are being measured correctly.
Clean the Mitutoyo calipers off with acetone or any other cleaning fluid suitable for precision instruments. Most Mitutoyo calipers are made from stainless steel, so use any cleaning fluids suitable for cleaning a metal of that type. By cleaning the calipers before calibrating, you will prevent dust, debris or metal chips from interfering with the process.
Close the calipers to set the dial to zero. You want the blades to be touching when the dial is reading zero. Hold the calipers up to the light and check for a gap between the blades. In order to have accurate measurements with your Mitutoyo calipers, the blades must be touching. Use a clean rag and compressed air to re-clean the blades if there is a gap.
Unscrew the nut on the top of the dial. This will allow you to reset the zero point with regard to the pointer. Spin the bezel until the arrow is pointing up to zero. Since these calipers measure in small increments as small as .0005 inches, you must make sure the pointer is directly at zero for your measurements to be accurate.
Tighten the screw after you have reset it, and, using the thumb screw, pull the calipers out a few inches. Push the blades back together a few times to make sure that the pointer is at zero every time. Repeat the process a few times while holding up at a light to look for gaps.
Measure with .25-inch, 1-inch, 2-inch and 4-inch precision blocks to make sure that the Mitutoyo caliper is reading accurately. These precision blocks are ground to be the exact sizes that they are marked within very tight tolerances of .0001 inch. By using them to calibrate your caliper, you will be sure that the Mitutoyo is measuring properly and that your parts will be well within the specifications of the print.
Never measure using pressure with a set of calipers; you may damage the device. So touch each side of the object you are measuring with a light touch.