DIAL / DIGITAL INDICATORS(Spindle Type)
Calibration Frequency: 12 months
(can be modified according to stability, purpose and usage)
1.0 Scope:
This method describes the calibration of spindle type dial /digital indicators.
Measuring range: 0 to 5 inches (0 to 125 mm).
2.0 References: This document is based on the NAVAIR procedure.
3.0 Definitions: TI: Test Instrument
NAVAIR: Navy Air Force
4.0 General Requirements:
Environment:
·Temperature: Change should not exceed 2 deg. F/h (1 deg. C/h).
68 ± 1 deg. F (20 ± 0.5 deg. C) is required for tolerances smaller
than ± 0.0001 inch (± 0.0025 mm).
· Humidity: No excessive humidity.
· Air quality: N/A.
Stabilization:
· Stabilize equipment and standard at ambient temperature.
A minimum of one hour is recommended.
Preliminary Operations:
· Clean TI.
· Verify TI for damage such as nicks or burrs.
· Ensure that the mechanical action of gaging mechanism is smooth with no
evidence of sticking or binding.
· Ensure that gaging tip is not loose.
· For dial indicators having a revolution counter, ensure that the revolution counter
indicates ± 0.5 DIV. of zero position counter when dial is zeroed.
· Ensure that indicator is perpendicular to standard.
Standards and Calibrating Equipment:
·The standards and equipment used must have a valid calibration certificate.
5.0 Equipment:The following equipment is considered a minimal requirement and any
equivalent equipment may be used.
1. Grade 0 Gage Blocks.
for a resolution greather than 0.0001 in. (0.002 mm), grade 2 Gage Blocks could
be used).
or indicator calibrator, uncertainty +/- 0.00005 inch ( 0.001 mm).
or supermicrometer, uncertainty +/- 0.00005 inch ( 0.001 mm).
2. Magnifying glass or microscope.
3. Indicator fixture or support (if required).
4. Grade A / Class 1 surface plate (if required).
6.0 Calibration Process: Use only the portion of the calibration method applicable
to the TI and use manufacturer specifications and limits
when available.
Item Test Characteristics Acceptance Limits Test Method
1 Graduations Good contrast Visual
2 Wear of gaging tip No flat on spherical Magnifying glass
or ball gaging tip or microscope
3 Repeatability Manufacturer’s specifications Gage block
verify at: 25, 50, and 75 or or
percent of full scale (5 readings) Digital: ± 1 graduation indicator calibrator
or
Dial: ± 0.2 graduation supermicrometer
4 Linearity Manufacturer’s specifications Gage block
verify at: minimum 4 positions or or
(8 positions is recommended) indicator calibrator
inward and outward direction ± 1 or ± 2 graduations or
supermicrometer
Digital:
Zero TI with a pre-load of
5 to 10 percent of range
Dial:
Zero TI with a pre-load of
¼ turn of the pointer on the dial
Example of a dial indicator
Resolution Reading Range
0.0005 0-20 0.050
Test: Inward Outward
Points: 0.012, 0.024, 0.036, 0.024,
0.036, 0.048, 0.012 and 0.000.
7.0 Notes:
1. Record readings, maintenance such as servicing, adjustment, repairs
or modifications.