In the elementary stage, a knowledge is required of the simple parts
only of _machines in common use_. _Some_ of these are enumerated in the
following list. The student should be practised in drawing them till he
recognises their forms, and the object of the arrangement should be
explained to him. He should also know the simple technical terms used in
describing them.
A few very simple questions relating to the arrangement, proportions,
and strength of the simplest machine details will be set in the
examination paper.
In drawing the examples set to test a student's knowledge and skill in
machine drawing, it must be remembered that only a limited time is
available. It is only possible to set an example to be drawn in pencil,
and the points which will receive attention are (1) accuracy of scale
and projection; (2) power of reading a drawing, shown by the ability to
transfer portions of the mechanism and dimensions from one view to
another; (3) knowledge of machines, as shown by the ability to fill in
small details, such as nuts, keys, etc., omitted in the sketches given.
Bearing in mind the limited time available, the student should try to
make his outline clear and decisive and complete. But the diagonal lines
necessary for sectional parts may be done rapidly, though neatly, by
freehand if necessary.
_Riveted Joints._--Forms of rivets and arrangement of rivets in lap and
butt joints with single and double riveting. Junction of plates by angle
and T-irons.
_Bolts, Studs, and Set Screws._--Forms of these fastenings. Forms and
proportions of nuts and bolt-heads. Arrangement of flanges for bolting.
_Pins, Keys, and Cotters._--Form of ordinary knuckle joint. Use of split
pins. Connection of parts by a key. Connection of parts by a cotter. Gib
and cotter.
_Pipes and Cylinders._--Forms of ordinary pipes and cylinders and their
flanges and covers.
_Shafting._--Forms of shafts and axles and of journals and pivots. Use
of collars and bosses. Half-lap coupling. Box coupling. Flange coupling.
_Pedestals and Plummer Blocks._--Simplest forms of pedestals and hangers
for shafts. Form and arrangement of brass steps. Arrangements for
fixing pedestals and for neutralising the effects of wear.
_Toothed Gearing._--Forms of ordinary spur and bevil wheels. Meaning of
the terms pitch, breadth of face, thickness of tooth, pitch line, rim,
nave, arm. Mode of drawing bevil wheels in section.
_Belt Pulleys._--Forms of belt pulleys for flat and round belts. Stepped
speed cones. Drawing of pulleys with curved arms.
_Cranks and Levers._--Forms of ordinary cast-iron and wrought-iron
cranks and levers. Modes of fixing crank pin. Modes of fixing crank
shaft. Double cranks. Form of eccentrics.
_Links._--Most simple forms of connecting rod ends, open or closed. Use
of steps in connecting rods. Use of cotters to tighten the steps.
_Pistons._--Simple forms of piston. Use of piston packing. Modes of
attaching piston rod.
_Stuffing-Boxes._--Simple form of stuffing-box and gland. Use of
packing. Mode of tightening gland.
_Valves._--Simple conical of puppet valve. Simple slide valve. Cock or
conical sliding valve.