Calibration Dial Indicator Procedures
Dial indicators are used to measure small distances. These gauges are sometimes called a dial gauge or dial test indicator and are found in most quality assurance laboratories. At times the indicators fall prey to faulty readings and require calibration. The best time to calibrate dial indicators is just before use to ensure the indicator gives you an accurate reading.
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Cleaning
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Clean all parts of the dial indicator with alcohol or solvent that will not leave a residue. Concentrate the cleaning on the tips of the indicator gauge. Also clean the calibration gage blocks. Once the indicator is cleaned, lock the dial into place. Make sure that the plunger on the dial indicator can travel its full length but still touches the base plate.
Setting
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Before placing any gage blocks between the plunger and the dial indicator's base plate, make sure that the very tip of the plunger barely touches the base plate. Once you have ensured the tip of the plunger is in place, adjust the dial's face until the gauge reads "O."
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Gage Blocks
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Gage blocks are certified by a National Bureau of Standards (NBS) authorized laboratory. The certification guarantees that the test blocks are the size indicated on each side of the block. Take the smallest block, generally .020-inches, and place it between the plunger tip and the base plate. You must get a reading of .020-inches on the dial. Raise and lower the plunger a minimum of two more times and record the readings.
Additional Tests
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Once you have tested the dial indicator with the smallest gage block, begin using the larger gage blocks. Eight different blocks ranging from .020-inches to 2-inches are recommended. Take each block and insert it between the base plate and the dial indicator's plunger, measuring each gage block a minimum of three times. Record all the measurement readings. If the dial indicator surpasses one indicating mark for every 2-1/3 revolutions of the dial gauge, the dial indicator fails calibration and requires repairs.
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References
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