# Elements of Mechanical Drawing: The Use of Instruments, Theory of Projection and Its Application to Practice, and Numerous Problems Involving Both Theory and Practice

D.C. Heath, 1904 - Mechanical drawing - 152 pages
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Page 3 - AB, in contact with this edge, then reverse the triangle so that both edge and line may be free from shadow, and move the edge of the triangle toward the line. If they coincide, the angle is 90�. If they do not coincide, and the vertex of the angle formed by line and edge is at the top, as shown by A, the angle is greater than 90� by half the angle BAG. If the vertex of the angle is below, the angle is less than 90� by half the amount indicated. TEST OF 45� ANGLE. — If the 90� angle is known...
Page 53 - Having given the major and minor axes. From the extremity of the major axis, draw B6 parallel and equal to half the minor axis; divide it into any number of equal parts; in this case six. Divide BG into the same number of equal parts. Through points 1, 2, 3, etc., on B6, draw lines. to extremity C of the minor axis. From D, the other extremity of the minor axis, draw lines through 1, 2, 3, etc., on BG, intersecting the above lines in points which will lie on the required ellipse.
Page 112 - First, the distance across the flats or short diameter, commonly indicated by H, and equal to one and one-half times the diameter of the bolt plus one-eighth of an inch, second, the thickness of the head, which is equal to onehalf its short diameter, third, the thickness of the nut, which is equal to the diameter of the bolt.
Page 50 - ... ellipse is a curve generated by a point moving in a plane so that the sum of its distances from two fixed points in that plane is constant.
Page 22 - Heavy lines on the shade sides of objects should be used, except where they tend to thicken the work and obscure letters of reference. The light is always supposed to come from the upper left-hand corner at an angle of 45�.
Page 11 - ... against the shoulder of the socket, then adjust the needle-point so that its point is even with that of the pen. When once properly adjusted the needle-point should not be changed. The needle-point is usually made with a cone-point at one end and a fine shouldered-point at the other. The cone-point should never be used, as it makes too large a hole in the drawing paper.
Page 34 - With centers A and B, and any radius greater than one-half of AB, describe arcs 1 and 2. Through the points of intersection of these arcs draw a line. Its intersection with the given line AB, or the arc of the circle ACB, will determine the required points.
Page 77 - Fig. 128 the lines CD, CB and CG are called isometric axes, and lines parallel to them are known as isometric lines. Planes including isometric lines are known as isometric planes. It is evident that only isometric lines may be measured, since they alone are equally foreshortened. Thus the isometric of the diagonals of the squares, AC and DB, are, of unequal length, although in the original cube we know them to be equal.
Page 101 - This spiral is frequently called the equiangular spiral, from the fact that the angle between any radius vector and the tangent to the curve at its extremity is constant.
Page 76 - This differs from the preceding in that one face of the object is parallel to the plane of projection, and the projection is made by oblique lines instead of perpendiculars as in orthographic projection.