Page 273 - Aeronautical Engineer Data Book

Basic mechanical design 219

BS 308
Tolerance characteristic
Straightness
Flatness
Roundness
Parallelism
Angularity
Squareness
Concentricity
Run-out
Total run-out

The
The tolerance frame
component
Tolerance value
0.1 A

Symbol for the
toleranced
characteristic
The relevant
datum
A
Fig. 12.4 Tolerancing symbols

can have several contradictory values (see
Figure 12.5).

12.4.1 General tolerances
It is a sound principle of engineering practice
that in any machine design there will only be a
small number of toleranced features. The
remainder of the dimensions will not be criti­
cal. There are two ways to deal with this: first,
an engineering drawing or sketch can be