Page 230 - Engineering drawing from first principles using AutoCAD

Technical drawinqs for industry 223

obviously competes against the clock, so guidance is often provided to assist in the
comprehension aspect. The following exercises are complete with solutions to assist in
understanding the linework, so that the draughtsman can gain engineering experience
and expertise.

Adjustable spanner

The component parts of an adjustable spanner are shown in Figs. 10.12 and 10.13. Copy
the given component details and then draw the following views:
• a front view of the assembled parts;
• a plan view;
• an end view.
The components are assembled using four 3mm diameter round-head rivets and the
heads of the rivets are shown in the front view as circles of 5mm diameter.

Solution notes
Copy the component drawings and dimension them as shown in Figs. 10.12 and 10.13.
Save both drawings on file. Study the assembly solution in Fig.l0.14. It can be con-
structed partly by manipulating the outlines already drawn like a jigsaw puzzle. Note that
three-quarters of the assembly is present in Fig. 10.12, so save this drawing using a new
file number to give the right-hand side of Fig. 10.15 and delete the dimensions. Increase
the drawing limits to suit A3 size, which doubles the size of the drawing sheet. Take a
second copy of Fig. 10.13, delete the dimensions and insert it onto Fig. 10.15 giving the
result shown. Use the MOVEcommand in the Modify menu to reposition the components
as shown in Fig. 10.16.
In CAD there is no point in setting out work twice. It is a relatively simple matter to edit
parts 3, 4 and 5 in their correct positions and delete surplus linework. Use ORTHO, SNAP
and ZOOM whenever possible. Please refer to the following notes regarding DXFfiles to
arrange the manoeuvre of placing one file into another. The result will be accurate
provided the original drawings have been prepared using ORTHO and SNAP for datum
purposes. This solution is shown in first angle projection.

Using DXF files
The drawing interchange format (DXF) is a valuable feature of CADsince it allows you to
move drawings from one file into another. Furthermore, the files do not have to be in the
same drawing software, but can be exported into other Windows applications provided
they are compatible; however, this needs to be checked and the importing procedure
confirmed at the receiving end.

Assume that the assembly drawing shown in Fig. 10.17 is to be inserted into a
frame. Step 1 requires a separate DXF file to be made. Select Import/Export from
the full File menu and a second menu will appear. Click on DXF Out. The dialogue
box in Fig. 10.18 appears and the file name STD349 (my own file number) is
inserted. AutoCAD LT appends . dxf to the file name. Click 01< and the command
line reads

Enter decimal places of accuracy (0 to 16) /Entities <6>
We require the entire drawing to be transferred: click OK, and the DXF file is made.
Open a receiving file containing a copy of the frame outline to Fig. 10.1 and saved
under a new file number. Again select the Import/Export option from the full File