When calibrating metrology equipment, it is important to remember some specific details about the instrument that you are working to calibrate. Each dimensional instrument has specifications that must be met and for some instruments, the calibration must be an ongoing process. With a Vernier caliper, however, once it has been calibrated, it will essentially stay calibrated until the end of time... or it is moved out of alignment somehow.
Here's what you need to remember as you calibrate your Vernier caliper:
Step #1: Make sure the jaws of the caliper are clean of any grease, dirt, or foreign debris that could cause a misalignment. It is critically important for a Vernier caliper to be clean as it is calibrated. Simple soap and warm water are often enough to clean one, but sometimes a heavier cleaning agent must be used, especially for tough grease. Avoid using steel wool.
Step #2: Make sure that the gear is able to move along the tracks freely. If the gear does not move smoothly, then chances are you've missed some dirt or debris during the cleaning process. Don't force the gear – simply take another moment to clean the Vernier caliper.
Step #3: Bring the jaws completely together. When you've done this, the reading on the caliper should be zero. If it is not, then this is the place to reset the dial so that it does read zero.
Step #4: Calibrate the OD jaws. For the first check on the OD jaws, insert a .5 inch block between the jaws of the caliper and then close the jaws so that each side touches the gauge block. Record the reading, then repeat with a 1 inch block and a 4 inch block.
Step #5: Calibrate the ID jaws. Repeat the steps as listed in Step #4. If you have another a calibrated caliper, you can instead compare measurements of the calipers set at 12.7 millimeters and adjust the non-calibrated caliper to the calibrated one.
Step #6: Check the height calibration. Using a surface plate, utilize a three standard sized gauge blocks and bring the jaws together on each of them. Record the readings.
You Will Also Need To Calculate Uncertainty
For many people calibrating their metrology equipment, Step #6 is the last step and they begin to work. Unfortunately this means they are still using non-calibrated equipment. When calibrating a Vernier caliper, it is also necessary to calculate the uncertainty of the calipers. This usually takes 3 specific readings so that you can determine your first set of uncertainties.
The second set of uncertainty that must be calculated is based on environmental conditions. Temperature, humidity, and even the resolution of the caliper itself can all lead to another type of uncertainty that must be accounted for during the calibration process.
By remembering these steps, you'll be able to effectively calibrate any Vernier caliper. Use them today to make sure that your dimensional instrument is always able to measure up!