Curved shapes are best sketched by first defining points along the curve, then lightly sketching the curve between the points. See Figure 4-7. Evaluate the accuracy and smoothness of the curve, make any corrections necessary, and then darken in the curve.
Circles can be sketched by sketching perpendicular centerlines and marking off four points equally spaced from the center point along the centerlines. The distance between the center point and the points on the centerlines should be approximately equal to the circle’s radius. See Figure 4-8.
Draw a second set of perpendicular centerlines approximately 45° to the first. Again mark four points approximately equal to the radius of the circle. Sketch a light curve through the eight points, and check the curve for accuracy and smoothness. Make any corrections necessary, and darken in the circle.
An ellipse can be sketched by first sketching a perpendicular axis, and then locating four marks on the centerlines that are approximately equal to major and minor axis distances. Sketch a light curve, make any corrections necessary, and darken in the elliptical shape. See Figure 4-9.
Figure 4-10 shows how to sketch a slot. To sketch the slot, centerlines for the two end semicircles are located and sketched. Two additional radius points are added, and then the overall shape of the slot is lightly sketched. Corrections are made, and the final lines are darkened.
The triangular object is first sketched as a triangle, guidelines and axis are added for the curved sections, and the final shape of the object is sketched.