the leadholder vertical and constantly against the inside edge of the hole pattern.

Check the finished circle with a scale.

There are many tools, other than the ones already presented,

which are used to help create technical drawings. One such tool is an adjustable

curve or snake, which is useful when drawing unusually shaped curves.

Another tool is the drafting machine.

A drafting machine is a combination

T-square, triangle, protractor, and scale which, when used properly, will greatly

increase drawing efficiency.

The information previously presented for using a

T-square, triangle, protractor, and scale may be directly applied to using a

This concludes the discussion on drafting tools. In the following paragraphs, we

will discuss the fundamentals of geometric construction.

3.

Geometric Construction

Geometric constructions are the building blocks of drafting.

Every drawing,

regardless of its difficulty, is a geometric shape. A rectangle is four straight

lines and four right angles. A cam is a series of interconnected arcs of various

radii. Every repair shop technician must have a fundamental knowledge of geometric

constructions if he is to progress to more difficult work.

In the following paragraphs, we will discuss some of the geometric constructions

that may be encountered.

a. * Points and Lines*. A point, to a draftsman, is defined as the intersection of

two construction lines (figure 20 on the following page).