Dial Test Indicator Calibration
The purpose of this procedure is to provide general instructions for the calibration
of dial test indicators.
All standard dial test indicators used to measure, gage, test, inspect and control
part compliance to customer specifications and drawings.
Preliminary Instructions and Notes
- Read this entire procedure before beginning the calibration.
- Calibration shall be performed in an environment that conforms to Manufacturer Specifications.
- The dial test indicator will hereafter be referred to as the Instrument Under Test
- Verify that the IUT is clean.
- Visually examine the IUT for any condition that could cause errors in the calibration.
- An error in zero setting during calibration will be contained in every measurement
and will increase in proportion to the distance from zero.
- If any of the requirements cannot be met, refer to the applicable manufacturer manual.
- If a malfunction occurs or a defect is observed while calibration is in progress,
the calibration shall be discontinued and necessary corrective action taken; if
corrective action affects a measurement function previously calibrated, the function
shall be recalibrated before the remainder of the procedure implemented.
Applicable Manufacturers Manual or Brochures.
The specifications of the IUT are determined by the applicable manufacturer's documentation.
If the manufacturer's documentation is not available, then the specifications identified
in this procedure are used.
Accuracy of all IUT's shall be within one dial graduation.
Repeatability of all IUT's shall be within 1/4 of one dial graduation.
The Standards listed below should be selected on the basis of their higher accuracy
level when compared to the unit under test. Equivalent Standards must be equal to
or better than the Minimum-Use-Specification.
Minimum-Use-Specifications for Standards listed are 1/4 the accuracy required by
Dial indicator checker with .0001" micrometer head, or equivalent.
Test indicator calibration arm.
- Using index finger, depress the IUT contact point slowly and evenly over the full
range, slowly allow the contact point to return to its starting position. The gage
pointer shall move freely (without binding) and should return to the same starting
- Securely position the attachment arm onto the indicator checker. The IUT shall be
mounted to the dovetail slot of the attachment arm to position the indicator contact
point with respect to the micrometer spindle of the indicator checker.
- Position the micrometer thimble and test indicator to obtain zero readings. From
this point, the gage pointer must travel the full indicator range, both clockwise
and counterclockwise directions if unit is bi-directional.
- Divide the total indicator range into four equal parts to determine calibration
- Advance the spindle of the checker that represents the lowest value selected in
step 4. Observe the location of the indicator pointer with respect to the dial graduations.
- Repeat all previous checkpoints in the opposite direction returning to zero.
- Repeat steps 5 and 6 a minimum of two additional times to determine IUT repeatability.
Any gage exceeding specified tolerances per 3.4 at any time during calibration shall
be repaired and recalibrated, returned as is for restricted use or scrapped.
All repair work shall be performed by a qualified individual.
Reason for Reissue
Revision A - First Release
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