measurement from a scale to the work, set one point of the dividers on the mark and carefully adjust the other leg to the required length, as shown in figure 2-5.

To scribe a circle, or an arc, grasp the dividers between the fingers and the thumb, as shown in figure 2-6. Place the point of one leg on the center, and swing the arc. Exert enough pressure to hold the point on center, slightly inclining the dividers in the direction in which they are being rotated.

TrammelPoints

To scribe a circle with a radius larger than your dividers, you should select TRAMMEL POINTS. The method of adjusting the points, as shown in figure 2-7, is to set the left-hand point on one mark, slide the right-hand point to the required distance, and tighten the thumbscrew. The arc, or circle, is then scribed in the same manner as with the dividers.

Constructing a 90-degree, or right, angle is not difficult if you have a true, steel square. Suppose that you have no square or that your square is off and you need a right angle for a layout. Breakout your dividers, a scriber, and a straightedge. Draw a base line like the one labeled AB in figure 2-8. Set the dividers for a distance greater than one-half AB; then, with A as a center, scribe arcs like those labeled C and D. Next, without changing the setting of the dividers, use B as a center, and scribe another set of arcs at C and D. Draw a line through the points where the arcs intersect and you have erected perpendiculars to line AB, forming four 90-degree, or right, angles. You have also bisected or divided line AB into two equal parts.

Constructing a right angle at a given point with a pair of dividers is a procedure you will find useful when making layouts. Figure 2-9 shows the method for constructing a right angle at a given point.

Figure 2-7. - Setting trammel points.

Figure 2-5. - Setting the dividers

Figure 2-6. - Scribing an acr/circle with dividers

Figure 2-8. - Constructing a 90-degree angle by bisecting a line.

Figure 2-9. - Constructing a 90-degree angle at a given point