TB 9-5210-205-50
9. Calibration for Flatness
a. Performance Check
NOTE
Handle blocks with gloves or forceps.
(1) Test the wringing surfaces of TI for flatness, as follows:
(a) Place TI on the platen of the interferometer and adjust until the desired
fringe pattern appears (B, fig.1)
(b) Arrange the fringes to appear first in one direction on TI and then the other.
(c) Interpret flatness errors from fringe patterns (B, fig. 1) and record four
results from each block (two from each wringing surface).
(2) The TI will not exceed the applicable flatness value listed in table 1.
NOTE
Since the majority of tolerance grades 0 and AS-1 blocks under
0.100 inch (2.5 mm) in length are not precisely flat, the test for
parallelism is considered sufficient. The interferometer will be
used to examine blocks under 0.100 inch (2.5 mm) in length for
scratches, dents, or other damage that would prevent accurate
calibration or usage. Blocks showing such damage will be
rejected.
a. Performance Check
(1) Arrange TI and gage blocks (hereafter called master block) side by side
according to size on soaking area.
(2) Allow sufficient time for normalizing of TI. Observe such factors as elapsed time
between handling and stability of room temperature.
NOTE
Handle blocks with forceps. Gloves may be used for blocks over
4 inches.
(3) Place master block on anvil of comparator and align master block so that
gauging head contact tips of comparator will contact reference point for length
measurement.
(4) Adjust the ZERO control to read the same as the recorded value found in the
test report for the master block you are using. Remove master block and insert TI.
(5) Take reading at reference point A (fig. 1).
(6) Record meter reading in millionths of an inch with proper signs on calibration
worksheet, this will be the length deviation of the TI.
