Introduction to Basic Manufacturing Processes and ... - always yours

468 Introduction to Basic Manufacturing Processes and Workshop Technology
Upper
deviation
Lower
deviation
Tolerance
Zero line
Basic size
Min. Limit
of size
Max. Limit
of size
Fig. 26.1 Basic size deviation and tolerances for both shaft and hole
26.3.3 Zero Line and Deviation
In graphical representation of limits, straight line to which the deviations are of zero
deviation and the represented of zero deviation are referred. The zero line is also known as
line of zero deviation is generally drawn as horizontal line and the positive deviations are
shown above this line and the negative deviations below it.
The algebraic difference between the actual or maximum size and the corresponding
the basic size is called deviation. The deviations from the basic dimensions at the
boundaries of the tolerance zone are called upper and lower deviations as depicted in
Fig. 26.2.
To le ran c e
Max. Dia
Min. Dia
Max. Dia
Min. Dia
Lower deviation
Upper deviation
Tolerance
Lower deviation
Upper deviation
Shaft
Basic
size
Zero line &
line of zero
deviation
Hole
Fig. 26.2 Upper and lower deviations for both shaft and hole
26.3.4 Upper Deviation
It is the algebraic difference between the two maximum limit of any size of the part and
the corresponding basic size.
26.3.5 Lower Deviation
It is the algebraic difference between the minimum limit of any size of the part and the
corresponding basic size.
26.3.6 Mean Deviation
It is the arithmetical mean between the upper and lower deviations of any size of the
part.