Machinery's Handbook, 31st Edition
800 CALIBRATION OF INSIDE MICROMETERS 6) Repeat Items to 5) for all remaining extension rods, sleeves and end caps in the set. Alternate Method: 1) Remove the shortest extension rod or one end cap used in the lin earity calibration, and replace with the next UUT extension rod in the set. 2) Wring together a gage block stack to achieve the nominal desired length of the micrometer head at zero indication and the included extension rod. 3) Wring, or attach using the accessory attachment rods, the outside caliper jaws to the gage block stack. Assure stack is square and true. Minimal force is required to secure the outside caliper jaws to the gage block stack. 4) For UUT with 0.0001 inch (0.001 mm) resolution, allow for 1 hour stabilization time for gage block stacks that are wrung to achieve nominal length over 8 inches (200 mm). 5) Use the UUT to measure the gage block stack. 6) Confirm that the measured value is within the tolerance limits as listed in the Table 4, Table 5, and Table 6 for the Type II Class 2, Type II Class 3 Style A, and Type II Class 3 Style B inside micrometer. 7) Repeat Items to 6) for all remaining extension rods, sleeves and end caps in the set. Calibration of Vernier, Dial and Digital Calipers Preliminary Operations.— 1) Review and become familiar with the entire calibration procedure before beginning calibration process. Ensure familiarity with setup and opera tion of all standards involved in the procedure. 2) Always observe safe handling methods for all standards and exercise caution in the handling of all precision standards. 3) Ensure the work area is clean, well illuminated, and free from excessive drafts and humidity. 4) Ensure measuring surfaces are clean and free of nicks and burrs that could affect the accuracy of the measurements. Observe the Outside Measuring Jaws and Inside Measur ing Jaws for any possible damage and observe the unit for wear or deformation or any con dition that may affect the parallelism of the measuring surfaces. Close the measuring jaws completely and tighten the lock screw. Hold the UUT in front of a strong light source and verify that there are no burrs on the OD or ID measuring jaws. If any condition of concern is observed in regards to nicks or burrs along the beam, light stoning with a hard Arkansas stone can be used with care to remove these incursions. 5) Observe the condition of the rack along the full length of a dial caliper to assure there is no damage to the rack gear tooth or embedded chips or dirt that will affect or damage the movement. Look for bent or damaged gearing. Open and close the slide slowly and listen and feel for evidence or broken or damaged drive pinion gear. 6) Assure that the movement along the length of the beam does not bind or indicate the presence of any nicks or burrs along the beam. Assure the movement is not too loose. Observe the position of the gib slide screws that they have not been removed or loosened. 7) Bring the UUT (Unit Under Test) into the controlled environment a minimum of 4 hours prior to beginning the calibration process. Allow all standards and UUT to stabilize to common temperature before proceeding. Table 19. Equipment Requirements and Minimum Accuracy Specifications of Required Standards
Recommended Measurement Standards
Minimum Use Specifications
Noun
Alternative
Range: 0.050 to 4.000 inch 2.0 to 450 mm 5 to 84 inch 125 to 500 mm
Starrett Webber SC 81.A1 Starrett Webber S2C 88.MA1 Starrett Webber SS 8.A1X Starrett Webber SS 8.MA1X
Mitutoyo 516-401-16 Mitutoyo 516-442-10 Mitutoyo 516-762-16 Mitutoyo 516-753-10
Gage Block Set Gage Block Set (Long Block)
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