Page 172 - Engineering drawing from first principles using AutoCAD

Pattern development 165

Figure 7.14

intersections on line 1 to 13. Ensure that you use the maximum ZOOM setting to give
the best results.
For the pattern construction, copy radii R2 and R3 from centre P, equal in length to
distances OC and 013. Draw one radial line PIon the pattern and use the method
described in the previous example to divide the pattern angle into 24 divisions. The total
number of items will be 25 (Fig. 7.15).
There are two particular points which should be added to the pattern drawing for
accuracy, and these are shown as Tl and T2. You will need to transfer two extra radial
lines on the pattern drawing. Draw a dotted line from centre 0 to point Tl, which is the
tangency point between the curve and line B1. The second dotted line is taken from
centre 0 through T2 to line B1. Point T2 is the tangency point between the straight line