MIL-P-288B
TABLE II.
Classification of defects. - Continued
Category
Defects
Carrying case, envelope or folder non-conforming (see 3.9).
202
Type II protractor non-conforming.
Body radius (see 3.6.2, 3.7.2).
203
Integral arm from center of circle (see 3.6.3, 3.7.3).
204
Arm taper width (see 3.6.3).
205
Fiducial line length (see 3.6.2).
206
Diameter and location of holes (see 3.6.3).
207
Movable arm(s) length (see 3.6.3, 3.7.3).
208
Graduation marks length (see 3.6.4, 3.7.2.2, 3.7.3).
209
Height of numerals on body and movable arms (see 3.6.4, 3.7.2.2).
210
4.5.2 Accuracy test. For testing the accuracy of the protractors, a metal
check plate, approximately 48-inches square in size, shall be used. The metal
plate shall be scribed with an accurate system of radial lines extending from
the center of the plate to the periphery at 15 degree intervals from 0 through
360 degrees. The radial lines shall be approximately 0.005-inch in width, and
shall be accurately scribed so that the angle between the fiducial line or
0-degree line and each radial line shall be accurate to within 1 minute of arc.
4.5.2.1 Accuracy test for type I protractors. The accuracy of the type I
protractor with arms fully extended shall be determined as follows:
(a) The left arm of the class 1 protractor or the right arm of the
class 2 protractor shall be held against the fixed arm and the
graduated circle and vernier shall be read to check the accuracy
of the zero setting.
(b) The center of either the class 1 or 2 instruments shall be accu-
rately located at the center of the system of radial lines on
the master check plate and the fixed arm shall be located
accurately along the 0-degree fiducial line. The left and
right arms in turn shall be set at 180 degrees on the vernier
and circle, and checked for coincidence with the 180 degree
mark on the master check plate.
(c) The fixed arm of the protractor shall then be rotated to a
random position on the master check plate, making certain that
the protractor is still accurately centered on this plate.
The protractor shall be anchored in this positicn by weights
16
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