about one grade softer than the pencil used forcorresponding line work. For dim constructionlines, use 4H to 6H leads. Avoid using leads thatare too short.The compass lead should be sharpened witha single elliptical face, as shown in figure 3-7, viewA. A sandpaper pad works best for sharpeningcompass leads. The elliptical face of the lead isnormally placed in the compass so that it facesoutward from the other compass leg. Adjust theshoulder-end needlepoint so that the point extendsslightly farther than the lead (fig. 3-7, view B).With the needlepoint pressed lightly in the paper,the compass should be centered vertically whenthe legs are brought together.Bow compasses and pivot joint compasses areused in the same manner. To draw a circle witha compass, lightly press the needlepoint into thedrawing paper and rotate the marking leg aroundit. Always rotate the compass clockwise. As yourotate, lean the compass slightly forward. Witha little practice, you will find that you can easilydraw smooth circles using only the thumb andforefinger of one hand. It is important that youuse an even pressure as you rotate the compass.You may find it necessary to rotate the compassseveral times to produce a circle with a uniformdense black line.When you wish to set the compass to draw acircle of a given diameter, use a piece of scratchpaper and follow the steps listed below,referring to figure 3-8.1. Draw a horizontal line with a straightedge.2. With the straightedge as a base, use atriangle and draw a vertical line intersecting thehorizontal line (fig. 3-8, view A).3. Measure the radius of the circle with ascale, as shown in figure 3-8, view B, and drawa second vertical line from this point.4. Set the needlepoint at the intersection ofthe first vertical line and the horizontal line (fig.3-8, view C). This is the center of the circle.5. Set the marking leg to fall on theintersection of the second vertical line and thehorizontal line (fig. 3-8, view D).6. Draw a half circle with the compassfig. 3-8, view E).7. Check yourdiameter established(fig. 3-8, view F).work by measuring theby this half circle with a scaleFigure 3-8.-Drawing a circle of a given radius.45.157Once You have set the compass to the exactradius of the circle, handle it very carefully so thatyou don’t disturb the setting. Set the needlepointat the center of the circle and carefully rotatethe compass to draw a line describing thecircumference of the circle. Do not apply toomuch pressure on the needlepoint or it will borea hole in the paper and you will lose the accuratecenter mark. To keep the diameter of the hole toa minimum, you may set the needlepoint of thecompass on a small strip of paper or thincardboard over the drafting sheet at the center ofthe circle.When you are using the pencil leg to drawcircles smaller than 1 in. in radius, keep theadjustable pencil and needle legs straight. Forlarger circles, both legs should be adjusted so thatthey are perpendicular to the paper. On the otherhand, when you are using the compass with thepen leg, you MUST adjust it at the hinge jointto keep it perpendicular to the paper for all size3-7
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