PRIN. OF DRAFTING AND SHOP DRAWINGS - OD1641 - LESSON 1/TASK 2
A line, to a draftsman, is an object line connecting two or more points (figure 21
on the previous page).
The accuracy of a curved line depends on the number of
points used to define it.
The number of points used
depends on the accuracy required for the particular curve.
b. Bisecting. Bisecting is the geometric way of finding the center of a line or
an angle. In the following subparagraphs, we will discuss the two procedures for
bisecting a line and the procedure for bisecting an angle.
(1) Bisect a Line - First Method (figure 22 on the following page). Let's assume
we are given a line (1-2, view A). Our problem is that we have to divide this line
into two equal parts.
To divide the line into two equal parts, perform the
Step 1. Construct an arc of radius R. Use point 1 as the center.
R = any radius
of greater length than 1/2 of line 1-2 (view B).
Construct an arc of radius R.
Use point 2 as the center (view C).
Define the intersection of the arcs as points 3 and 4 (view C).
Connect points 3 and 4 with a construction line (view D).
Step 5. Define point S where line 3-4 intersects line 1-2.
Line 1-5 is equal to
This is the classical method as taught in plane geometry.