Page 62 - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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Table 1.20 Terminology used on drawings
Sections When the inside details of an object are important it is often convenient to show this by sectioning or cutting
the object in a suitable place. A sectioned view of a brake cylinder is a good example
Dimensions Lines with arrowheads in some cases simply show the size of the object. These are used more for drawings
used to make an item than to pass on information for repair
Tolerances Dimensions can never be completely accurate, although they are very close in some cases. A good example
and limits of a tolerance or limit on a motor vehicle drawing is the bore of a cylinder given as 70 0.05 mm

Fits Two types of ‘fi t’ can be used. Clearance fi t is where, say, a pin is slightly smaller than, and therefore slides
into a hole. Interference fi t is where the pin is very slightly too large and needs pressing into the hole
Projection A term used to describe the way an object is drawn. You can imagine it as if projected on to a screen from
different angles
Line diagram A simplifi ed diagram showing only the most basic of information
Block Complicated systems can be simplifi ed by representing, say, the fuel system as one block and the engine as
diagram another, and so on
Exploded This is often used in workshop manuals. It shows a collection of components spread apart to show their
diagram details and suggest their original positions

Table 1.21 Sources of drawings and other information

Technical Sheets of information sent from manufacturers to the dealers outlining the latest repair information
bulletins
Parts The pictures or drawings in parts books are useful for repair procedures as they often show all the component
books parts of an object
Textbooks This one is the best, of course, but a number of other good books are available
Workshop These are the traditional source of detailed information on specifi c vehicles and systems
manuals
Microfi che A microfi lm is often used to store pictures and information, as a large amount can be stored in a small space. It

is like a very small photographic negative read on a viewer. Not used much nowadays
Computer The computer is increasingly becoming essential in many ways. A large amount of data can be kept on disc
and retrieved with a few key strokes
CD and One DVD can hold a massive amount of information (equivalent to many workshop manuals), which can be
DVD accessed quickly and easily by a computer
Online Many sources of information are now available on line. This means that with a computer and modem you can
databases access remote databases

long thin chain ___ _ ___ _ ___ centre lines
●
long chain ___ ___ ___ ___ cutting planes
●
There are many types of drawing methods and some of these are outlined in
Table 1.20 . There are many sources of information that use drawings; some are
outlined in Table 1.21 .
Drawings can be produced in a number of ways. The most ideal for engineering
drawings are as follows.
● Orthographic projections show three elevations, usually a front, plan and end
view.
Pictorial projections, such as isometric and oblique, show a representation
●
of what the item looks like. The isometric view is used often in workshop
manuals to show the arrangement of a complicated system.