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Home > Education >Dial Caliper Information

Use the dial calipers right

Measurement results are limited by the condition of the gage and the manner in which it is used. Adhere to the following guidelines and you can expect good results:
Care and respect--All hand tools must be treated with care and respect. Don't use them for other purposes (such as prying things apart or hammering things together). Wipe the tools clean after using, and don't throw them on the workbench. For dial calipers, be particularly wary of dirt, which can accumulate on the rack, throwing measurements off and ultimately damaging the indicator. Store a tool in its case. If it's going to be there for a while, apply a thin coat of oil to the jaws to inhibit corrosion.
Wear--Check the tools often for wear, as well as burrs and scratches on the jaws and contacting surfaces. In the case of a caliper, a simple way to do this is to pass a master disc along the jaws while inspecting for wear or taper.
Calibration--All measurement tools need to be calibrated at least once a year, more often with heavy use or multiple users. Fixed gages are sent to a calibration room where the plug or ring is measured for size and compared to a tolerance specified by the gage's classification. It can also be measured at multiple locations to inspect for form errors and will be visually inspected for scratches and nicks.
Gage resolution--Before you pick up a tool to measure a part, make sure it has the resolution you need. The rule of 10 says that a measurement tool should have 10 times more resolution than the tolerance of the dimension. Calipers typically read in 0.001 in. or 0.0001 in. units, so if the tolerance is tighter than 0.0005 in., a higher-accuracy gage is needed.
"Feel"--Positioning hand measurement tools and interpreting the measurement results require skill. As users develop their "feel" for the tool, measurement results become more consistent. Although the addition of digital readouts may remove some of the guesswork, applying the tool properly will still require skill. Find some time to practice with all of your measurement tools.
Special tooling--Some parts will require special tooling to ensure that the critical dimensions can be measured quickly and reliably. A good example is the metal-forming process used to manufacture aluminum cans: Trying to hold a can and measure it is self-defeating because the can distorts. One solution is tooling a fixture to "round up" the part for diameter measurement.