Explanation Of Terms For Maintenance Standard - Komatsu 80001 Shop Manual

00 Index and foreword

Explanation of terms for maintenance standard

The maintenance standard chapter explains the criteria for replacing or reusing products and parts in the
machine maintenance work. The following terms are used to explain the criteria.
1. Standard size and tolerance
To be accurate, the finishing size of parts
q
is a little different from one to another.
To specify a finishing size of a part, a tem-
q
porary standard size is set and an allow-
able difference from that size is indicated.
The above size set temporarily is called
q
the "standard size" and the range of differ-
ence from the standard size is called the
"tolerance".
The tolerance with the symbols of + or – is
q
indicated on the right side of the standard
size.
Example:
Standard size
120
a The tolerance may be indicated in the text
and a table as [standard size (upper limit
of tolerance/lower limit of tolerance)].
Example) 120 (–0.022/–0.126)
Usually, the size of a hole and the size of
q
the shaft to be fitted to that hole are indi-
cated by the same standard size and dif-
ferent tolerances of the hole and shaft.
The tightness of fit is decided by the toler-
ance.
Indication of size of rotating shaft and hole
q
and relationship drawing of them
Example:
Standard size
60
PC130-8
Tolerance
–0.022
–0.126
Tolerance
Shaft Hole
–0.030 +0.046
–0.076 +0
SEN03766-01
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