Page 36 - Engineering drawing from first principles using AutoCAD

Geometrical applications 29

R80

- R(80-20)

R(50+20)

X
R20

-R50

Q
---

p! z

70
I
040
9 0 LO

032

I... 026 ..I

Figure 2.1

in Fig. 2.2 and then using the FILLET feature previously described to insert the R20
radius. If the arc resulting from the use of the FILLET feature is the first to be modified
into a polyline, it will then be possible to define the tangency points at each end. Clean up
surplus construction lines from the other two arcs and add the lower details shown. Use
the MIRROR feature described in Chapter 1 by enclosing your profile in a box from A to B
and clicking twice on the mirror line.

Film reel

The dimensions of one-quarter of a symmetrical film reel are shown in Fig. 2.3. Set out
the profile shown and insert the four corner radii using the fillet feature. Use the
MIRROR command about the OY axis to obtain half of the reel and again about the
horizontal axis to complete the drawing (Fig 2.4).