A-A-52034 Drafting Instrument Sets And Drafting InstrumentsThis specification covers four drafting instrument sets, and individual drafting instruments. The drafting instruments are intended for use by architects, engineers, scientists and draftsmen for general drafting practice.

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A-A-52034A

minutes of the angle specified. The outside or ruling edges shall be straight and true within +0.003 inch. The surfaces of the triangle shall be flat and true within 0.010 inch.

TABLE II. Triangle Thickness

1/ These are thickness limitations, not commercial standard thicknesses.

Contour ruling pen. The contour pen shall consist of a pen blade assembly attached to a thin rod which rotates in a tubular handle. The pen shall be constructed so that the blades are offset to the centerline of the handle and swivel without binding. A locking device shall hold the blades in a fixed position and a knurled-screw shall permit adjustment of the blade points. The pen shall conform to the size and design shown in figure 1.

Railroad ruling pen. The pen shall consist of two pairs of pen handles with a tubular handle constructed so that the pairs of pen blades shall turn freely or remain fixed on the handle as desired. The pen blades shall be tuned so that the points are eccentric to the center line of the handle, similar to the design of a contour pen in order that the pen blades will readily follow sharp curves. The overall length of the pen, including the handle shall be 5.25 inches. The pen shall be designed to provide lightness, good balance, and ease in handling.

Curve. Curves shall be furnished by pattern numbers 1 or 2 (see figure 2), in sets or individually as specified. The size of the curves shall be the size regularly produced by manufacturers of this type of curve. Curves shall be methacrylic plastic or acrylic plastic.

Large friction compass. The large friction compass shall be between 6 and 6.5 inches long, and shall permit drawing circles from 0.062 to not less than 5 inches in diameter. The friction shall be sufficient to hold the dividers in any position during normal use. One leg of the compass shall be provided with a removable and