V-BLOCK CALIBRATION Table 12. Equipment Requirements Table 12. (Continued) Equipment Requirements Machinery's Handbook, 31st Edition
744
Item
Minimum Use Specifications
Calibration Equipment Examples
Alternative Equipment Requirements
Range: 0 in. to 12 in.; Accuracy ±50 µ in over 12.00 in.
SquareMaster Master Square
PMC/Mercury SquareMaster Model VSQ-12
Range 3 in. W × 5 in. L × 12 in. H SquareMaster Master Square
Range to fit max diameter of UUT. ( Example: 5 in. × 12 in.); Accuracy: 100 µ in
Cylindrical Square Taft Pierce Model 9143 Preliminary Operations.— Review and become familiar with the entire procedure be- fore proceeding with the calibration process. Alternative standards may be substituted for the ones listed in Table 12. Equipment Requirements. Thorough consideration must be paid to the Accuracy Ratio , Total Accuracy Ratio (TAR) , and Measurement Uncertainties introduced when substituting standards. Some standards represented do not offer a 4:1 TAR. If this is an unacceptable condition according to your particular quality assurance system then measures must be taken to calculate the uncertainty and introduce this into your uncertainty budget, or determine the acceptable tolerance limits through Guard Banding or similar method to satisfy the requirements of your quality system. • Allow all the components to stabilize a minimum of 4 hours to the temperature of the calibration area before beginning the procedure. • Clean and closely inspect all critical surfaces for nicks and burrs. Carefully stone with fine hard Arkansas stone to remove any incursions. • Turn on electronic indicator and allow to warm up for a minimum of 30 minutes before proceeding. Calibration Procedure Note: Document the results of all measurements and tests for future reference, Trend Analysis, Root Cause Analysis or Calibration Interval Adjustment. Sides Square To Each Other.— 1) Set up equipment as shown in Fig. 11. a) Special attention must be paid to establishing ZERO indication at the height of the V-block (UUT or Unit Under Test) sides to be measured. The SQUAROL (squareness checker) is rotated so the crest of the radius is indicated by the lowest reading on the Electronic Indicator. Plus and Minus travel must be available on the indicator head.
Squareness Checker: Set to Height of V-Block
Granite Square Master
Surface Plate
Fig. 11. 2) Set the electronic indicator to the appropriate range to measure the Squareness of the Side A of the UUT. a) ±0.0002 in. for Grade A. (±0.0005 over 5 in.) b) ±0.002 in. for Grade B (or C) 3) Set the gage head of the electronic indicator against the granite square master at the appropriate height to measure side A of the UUT at approximately 90% of it vertical height. Rotate the Squarol to seek the lowest indication. Using the fine adjust of the Squarol to bring the reading close to the zero indication. Assure that plus and minus travel can be realized.
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