Machinery's Handbook, 31st Edition
CALIBRATION OF INSIDE MICROMETERS 799 3) For UUT with greater than 0.0001 inch (0.001 mm) resolution, gage block stacks that are wrung together to achieve the nominal setting dimension over 8 inches, must soak for one hour before establishing the setting dimension. This does not apply to single gage blocks used as setting standards. 4) Set the Reference of the supermicrometer or standard measuring machine to zero. 5) With the UUT set to zero, place into the measuring plane of the supermicrometer or standard measuring machine and measure the UUT. Assure that the UUT is supported on either a flatted round or adequate support to allow it to maintain alignment with the axis of measurement of the standard. 6) Verify that the measurement is within the tolerance limits for the UUT. Refer to the tolerance tables for the Type II Class 2 (Table 4), Type II Class 3 Style A (Table 5), and Type II Class 3 Style B (Table 6) for applicable tolerance limits. 7) Remove the UUT from the standard and set to the next test point as defined in Table 12 for the 1 inch (25 mm) micrometer head. 8) Repeat Items 5) and 6) for all remaining test points. Alternate Method: 1) Install the shortest extension rod or end caps and set UUT to zero on the micrometer head. Wring together appropriate size gage blocks to measure the zero indication assembly. 2) Wring or attach the Caliper Jaw End Blocks from the gage block accessories and assure the setup is square and true. If using the connecting rods, minimal force is required to secure the end blocks to the gage block stack. Note: For UUT with greater than 0.0001 inch resolution, gage block assemblies longer than 8.00 in (200 mm) will require 1 hour stabilization time before taking measurement. 3) Use the UUT to measure the gage block stack. Care must be taken to assure that the measurement is taken at the shortest distance between the caliper end block faces.
20 0
0 9 8 7
Gage Block Stack
Fig. 27. Inside Micrometer Gage Block Stack Measurement 4) Repeat Items to 3) for each remaining test point. Measure each gage block setup and assure that the indication is within the tolerance limits as defined 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 micrometers. Extension Rod Calibration.— Preferred Method: 1) Remove the shortest extension rod or one end cap used in the linearity calibration and replace with the next UUT extension rod in the set. 2) Ensure the Standard Measuring Machine has retained its reference. Verify the zero setting if necessary. The Supermicrometer will require re-mastering every 1 inch and can only be used up to 10 inches (generally). The standard measuring machine uses a continu ous measurement path but must be re-mastered every 8 inches. 3) 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). 4) Using a flatted round or appropriate supporting device, mount the UUT into the stan dard. Assure the alignment of the measuring path and measure the UUT. 5) Confirm that the indication 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.
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