Elements of mechanical drawing by Jamison Alpha Pierce

Author:Jamison, Alpha Pierce. [from old catalog]
Language: eng
Format: epub, pdf
Tags: Mechanical drawing
Publisher: New York, J. Wiley & sons;
Published: 1911-03-25T05:00:00+00:00

machine for accurately cross-hatching surfaces. It is a convenient but costly device, and as cross-hatching is done in a number of abbreviated forms and is not required to be accurate a section-liner is not a necessity to the draughtsman.

109. Erasing-shields. — This is a device of thin material, amber and various metals, with various shaped and sized openings, designed to mat out portions of a drawing to be erased.

no. Protractors.—A protractor is a device graduated in degrees, and is used in laying off angles not obtainable with the triangles and T-square. Protractors may be had of various materials, the best being of metal.

in. Scale-guard.— A scale-guard is an attachment for the triangular scale and is of use when one scale only is in constant use, as it enables the draughtsman to keep that scale always before him.

112. Proportional Divider.—The proportional divider is a double-ended pair of dividers provided with an adjustable clamp which enables the draughtsman to set one end of the tool at full size, and by means of the adjustment the other end is made to be some proportional size, as \ size, \ size, etc. Their use is obvious.

113. Erasing-knives.—Erasing-knives are a valuable addition to a drawing outfit; but as most draughtsmen are possessed of a pocket-knife, such a knife, well sharpened, answers all practical purposes.

114. Soapstone Pencil.— Soapstone is used to resurface the surface of tracing-cloth after an erasure has been made.

115. Paper.—Having discussed ways and means of constructing drawings, it now becomes necessary to select some material on which to construct the drawings. For this purpose any smooth surface will answer, shopmen often using the shop floor, a board, the wall, a blackboard, etc., for rough, free-hand, temporary sketches; however, the draughtsman's work is supposed to have finish, accuracy, to be permanent, in short, to be valuable, and for his purposes the field is limited to cloth and to paper.

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