Page 273 - Engineering drawing from first principles using AutoCAD

266 Engineering drawinq [rom first principles

You will also see that the alternative arrangement shown in Fig. 10.40 is a valid third
angle projection but does not fit into the frame. There is another possible group with an
end view to the right of the front view. This is obtained by looking from the right-hand
side of the front view, and it conveniently fits into the space. This alternative end view
will show the end of the spindle and parts of the pin through the spindle.

Exercise 10: hook and pulley assembly

The components are given in Fig. 10.41 and we are required to draw the details and
assemble the parts to give a front and an end view. It is normal practice only to draw
sufficient views of components to describe fully their shape and form. Study the
details and note that the hook, pulley, spindle and pin do not need another view.
The centre part of the support block is rectangular and requires a second view. The
second view for the side link and the washer are given to confirm the thickness. All
of these items would appear as shown here in first or third angle presentations. The
nut is drawn in third angle projection and the position of the chamfer circle in the
top view confirms that this is a third angle projection. In the case of the locknut
below, this would look exactly the same in first or third angle. The views given do
clarify the fact that the locknut is chamfered on both sides, whereas the nut is
chamfered on one side only. Note also, for the nuts, that the minor thread diameter
is drawn as a complete circle but the major diameter is broken. This is 'the standard
convention for female threads.

The assembly drawing is presented in third angle projection (Fig. 10.42). If, however the
tip of the hook was not shown in the right-hand view, then the drawing would be in first
angle.

Exercise 11: machine vice
The component parts of a machine vice are given in Fig. 10.43. All components are drawn
in first angle projection. Draw the following views of the vice with a circular bar 25 mm
diameter and 120mm long held in the jaws:
• a sectional elevation with the section plane taken along the centre line in the plan view;
• an outside plan view.
Do not include any hidden details in either view.
Note the diagonal lines showing spanner flats at the end of the spindle. The spindle
rotates in the sliding jaw and is retained in position by the two M3 screws. The two side
brackets guide the sliding jaw along the grooves at each side of the vice. Cross-hatch your
solution as shown in the assembly drawing and include the section plane and part
numbers. The first angle solution is shown on Fig. 10.44.

Exercise 12: special purpose clamp

Figure 10.45 gives the component parts of a clamp designed to support a cylindrical
assembly, which has overall dimensions of 40mm diameter and 50mm height resting on
a stop (part 9), while further work is undertaken. Draw the given parts and the assembly
showing two sectional views and a plan. As previously described, try to use the compo-
nent views where possible to build up the assembly. The first angle solution is given on
Fig. 10.46.