Page 4 - Engineering drawing from first principles using AutoCAD

Preface

Thank you for your interest. My first introduction to the subject of technical drawing
came at school, when at the age of 11, we started woodwork lessons. At the first meeting
of the class Mr Munday, our teacher, told us that we would draw working plans of a
simple joint. We were introduced to a drawing board, tee square, set of instruments, one
sheet of snowy white paper and two paper clips. We were shown the principles of simple
projection and then proceeded to copy views of a Lap Joint from the blackboard. I
instantly found this to be a very agreeable relaxing exercise. The controlled use of the
pencil, rule, square and compasses also enabled those of us without natural skills in
freehand art and painting to be 'in with a chance'.
At the next lesson we were taught how to prepare the wood, cut and make the two parts
and finally check the accuracy of the assembled joint. In addition we could see every edge
and corner represented by lines on the drawing.

This particular subject at school was especially popular with the other lads and the
general class atmosphere very stimulating and rewarding. When the results compared
favourably with the initial drawings I felt that I had really achieved something and
soon developed a strong desire to continue studies. We all also took great pride in
trying to keep the paper nice and clean and free of pencil smudges. I also always
enjoyed the subject of Applied Geometry which is logical and required more construc-
tional work on the drawing board.
When I left home in the mornings for school it was not uncommon to see a new
neighbour of ours leaving for work. He was smartly dressed and carried a leather brief-
case. Out of curiosity I asked my mother what Mr Oram did for a living and she found out
that he was a draughtsman and made 'plans'. I decided that this was quite a likely career
for me and it certainly gave me some sense of purpose at school when I realised that you
could actually get paid good money for doing something you really enjoyed. I later
bought a small drawing board and tee square for use at home and copied examples
from books in our local library and found that regular practice soon improves
technique.
Pencil drawings are easily corrected but damage to the paper may arise. More impor-
tant drawings for manufacturing and publication purposes were required to be pro-
duced in ink. This was a skill requiring lots of patience because ink is reasonably
permanent and extensive errors on some surfaces needed a redraw. In industry, it was
not uncommon for ink tracers to be employed to trace over pencil drawings onto
transparent film after original designs had been produced, checked and approved.
These days with the aid of a computer it is not necessary to worry about the state
of the paper or the need to trace the finished designs to obtain a truly professional
result. No need to keep sharpening the pencil to obtain consistent line thicknesses, no
need to worry about spelling mistakes after you have inked in notes when you have
otherwise nearly finished your work of art.
Variations in the height and slope of letters and numbers during dimensioning always
used to separate the beginner from the professional and often spoil an otherwise sound
drawing. These days lines and letters are all standardised and a spell checker available at
the touch of a button, but it is still necessary for the draughtsman to be completely in