Machinery's Handbook, 31st Edition
CALIBRATION OF OUTSIDE MICROMETERS 793 gage block stack will give an accurate reading. Assure the reading is repeatable. The reading must meet the tolerance limits as defined in Table 21a and Table 21b for Indicated Measurement Error . 5) Repeat these steps for each remaining gage block stack and record readings for evaluation or trend analysis. Follow all guidelines of the quality assurance programs in place in regards to recording and retaining all data collected and reporting OOT (out of tolerance) conditions. 6) For Interchangeable Anvil Micrometers , after calibration of the micrometer spindle thread, repeat Items 1) and 2) for each anvil in the set. Once the micrometer spindle thread accuracy has been confirmed, only the zero setting of each interchangeable anvil needs to be calibrated. Verify that each interchangeable anvil meets the tolerance limits assigned and record any OOT conditions before adjusting to meet tolerance limits if necessary. Calibration of Depth Micrometers Note: Do not lock the micrometer head without the depth rod installed. This could result in damage to the split ring locking mechanism causing the rods to bind. Flatness Calibration.— 1) For Depth Micrometers with a resolution of 100 μ in (or met- ric equivalent) or better, the Van Keuren model U6 Monochromatic Reflex Interference Viewer is used to observe the base flatness of the depth micrometer directly through an optical flat. The same technique of fringe count can be utilized to obtain the flatness as is used for the OD micrometer anvil and spindle ( Interpreting Optical Flat Fringe Patterns ). 2) For Depth Micrometers with 0.001 inch (0.01 mm) resolution per division, place the UUT on an individual 1.000 in (25 mm) gage block with the depth rod extended through the center relief hole as shown in Fig. 24. Bring the depth rod into contact using the ratchet stop or friction thimble and observe the reading. Repeat this measurement three times ensuring repeatability of the reading. Record the reading as reading A . 3) Remove the UUT from the setup and place it on two gage blocks (or stacks) of 1.000 in. (25 mm) as shown in Fig. 24. Bring the depth rod into contact using the ratchet stop or friction thimble as in Item 2) and observe the reading. Repeat this measurement three times ensuring repeatability of the reading. Record the reading as reading B . Subtract reading B from reading A and ensure that the result is within the tolerance limits as listed in Table 14. Table 14. Depth Micrometer Base Flatness Range Tolerance Inches Millimeters (inch) (millimeters) All with a resolution of 0.0001 in. or 50 m in All with a resolution of 0.0025mm or 0.001mm 0.0001 0.0025 All with a resolution of 0.001 in. All with a resolution of 0.01 mm 0.001 0.01 Note: The Linearity of the UUT is checked using the 0–1 inch (0–25 mm) depth rod only. Once the accuracy of the Micrometer Head has been verified, the remaining depth rod extensions are calibrated at the zero position only. It is critical to the outcome of the cali bration of the entire set that the base zero setting for the micrometer sleeve and thimble be accurate and without error or deviation. Any error in the base zero setting will cause errors to be translated to the depth rod extensions. Linearity Calibration (Depth Micrometers).— 1) Select the appropriate gage blocks to make stacks to measure 0.210, 0.420, 0.605, and 0.815 inch, or 5.10, 10.20, 15.30, 20.40, and 25.00 mm. The 1.000 inch (25.00 mm) block will also be used as the micrometer head will be calibrated at zero to full scale. Clean and wring gage blocks assuring no dirt or foreign matter is present.
Copyright 2020, Industrial Press, Inc.
ebooks.industrialpress.com
Made with FlippingBook - Share PDF online