How to Use the Instruments 27

For right-handed draftsmen, all horizontal lines are ruled from left to right; vertical lines which are drawn against the left side of the triangle are drawn up, and vertical lines ruled against the right side of the triangle are drawn down. The point of the pen must never quite touch the guiding straight edge, and this will not happen if the pen is not inclined either toward or away from the draftsman. The pen should be pressed against the straight-edge with only enough force to keep it in place; and no great pressure should be made on the paper.

The pen is to be held by the thumb and the first two fingers, and grasped somewhere be tween the thumb-screw and the end of the handle, according to the convenience of the draftsman. To insure a line of even width throughout, the pen must have no motion except along the paper in the direction of the line being drawn.

An exception to this latter statement must be made for inking lines with the irregular curve; for then, besides holding the pen nearly vertical, it must be turned slightly in the fingers when passing around a sharp curve, so that the points may remain in the same position relative to the curved edge, and the inked line thereby retain the same width.

When inking fine lines, care must be taken to clean the pen frequently, as, with a fine line, there is a tendency for the ink to cake on the end of the pen. It is very convenient when inking, to have at hand a small glass of water, into which the pen may be dipped when it is to be cleaned.

There are three features of a good ink draw ing—first, ink lines which exactly cover the original pencil lines; second, lines similar in character showing uniformity in width; and third, lines smooth and clean-cut in appearance, instead of broken and fuzzy.

43. To ink with the compass, it is necessary, for the best results, to have the legs of the instrument bent so that each is perpendicular to the paper. When it becomes necessary to use the lengthening bar, one hand should grasp it lightly near the end so as to steady the pen as the circle is drawn.

44. To Sharpen the Pen. Unless the pens are in good condition, satisfactory work is diffi cult or impossible to obtain. Every draftsman should be able to keep his pens in good condi tion, and with care and practice he will be able to do this. After considerable use, the proper elliptical shape of the pen points will wear off, and the pen will no longer work well. The draftsman should then take the oil-stone, and, after screwing the points of the pen close together, draw it with a rocking motion to and fro on the stone, keeping the pen in a plane perpendicular to the face of the stone. This process—which, of course, still further dulls the pen—is to restore the points to the original shape. After the proper elliptical shape has been produced, the pen should then be held at only a slight inclination with the surface of the stone, and then rubbed, first on one side and then on the other, until the points are suffi ciently sharp. Through all the process, the points should be kept screwed tightly together. No grinding is to be done on the inside of the pen.