Page 39 - Engineering drawing from first principles using AutoCAD

32 Engineering drawing [rom first principles

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R20

R12-
R24 BOTILE OPENER

Figure 2.5

Restaurant sign

The example requires you to change the paper settings to a landscape-style drawing (Fig.
2.6). It is also necessary to establish the position of the centres and tangency points in
connection with the RIS arcs. Change the SNAP settings temporarily to fix the centres for
the eye.

Metal worker's dolly

Draw the profile of a metal worker's dolly shown in Fig. 2.7. The curve XYZ is a semi-
ellipse. The dolly is supported by the taper. Thin sheet metal may be hammered into
shape on the top surface.

Telephone receiver

Commence drawing the outline of the telephone receiver in Fig. 2.8 by setting out the
major axes and positioning the two centres marked A and B. You may find it beneficial to
draw the profile in simple construction lines and then modify the outlines into polylines.
Use the FILLET command when appropriate and where the program automatically trims
some construction lines, it is a simple matter to reinsert them again, if essential, before
proceeding.
The example requires you to establish the centre of the R300 arc from the centres A and
B, and it depends where you start the drawing on the sheet, but it may be necessary to
reposition the illustration before printing. Remember to use the SNAP feature whenever
possible. Check the position of all tangency points so that you obtain smooth accurate
curves.