A-A-52024
Class 1 – 0 to 90 degree quadrant dial.
Class 2 – 0 to 360 degree circle dial.
Style A – with ball and socket joint, or ball and socket head, Jacob’s staff.
Style B – Without ball and socket joint, or ball and socket head, and without Jacob’s staff.
Dial Marking. Class 1 and class 2 compass dials shall be graduated in 1 degree increments. Every increment shall be marked with a tick mark. Every tenth degree shall be numbered (i.e. , 10, 20, etc.)>
Class 1. Class 1 compass dials shall be divided into 90 degree quadrants. The zero degree graduation shall be in the North and South directions. The 90 degree graduation shall be in the East and West directions.
Class 2. Class 2 compass dials shall be graduated in a complete circle. The zero degree graduation shall be in the North directions, the 90 degree graduation shall be in the East directions, and the 180 degree graduation shall be in South direction.
Material.
Metal. The metal, except that of the needle, shall be nonferrous and corrosion resistant. Needles shall be plated or otherwise durably coated to render them corrosion resistant.
Compass box. The compass box shall be a non-magnetic material and shall have a transparent window affording full visibility of the azimuth scale, the clinometers level vial scale and index, and the compass level vial. The compass box shall have an external screw driver-type adjustment so that the azimuth scale can be rotated with respect to the index.
Magnetic needle. The magnetic needle shall have magnets permanently attached or shall be magnetized to be sensitive to the earth’s magnetic field. The needle shall be designed and constructed to assure long retention of magnetism and shall indicate magnetic North when the box is rotated 360 degrees. The needle shall be freely supported on a pivot of nonmagnetic hardened material that provides minimum friction. The needle shall be designed in such a manner as to permit use or be provided with a balance weight which can be moved readily to any position and on either end to assure correct balance in any latitude between 85 degrees North magnetic latitude and 65 degrees South magnetic latitude. The needle shall be self-aligning to accurately indicate direction of magnetic North and shall be marked to readily indicate North. The ends of the needle shall be tapered to a fire point or
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