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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 is
a little different from one to another.
•
To specify a finishing size of a part, a tempo-
rary standard size is set and an allowable dif-
ference from that size is indicated.
•
The above size set temporarily is called the
"standard size" and the range of difference
from the standard size is called the "toler-
ance".
•
The tolerance with the symbols of + or – is in-
dicated on the right side of the standard size.
Example:
Standard size
120
★ 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 the
shaft to be fitted to that hole are indicated by
the same standard size and different toler-
ances of the hole and shaft. The tightness of
fit is decided by the tolerance.
•
Indication of size of rotating shaft and hole
and relationship drawing of them
Example:
Standard size
60
00-10
(14)
EXPLANATION OF TERMS FOR MAINTENANCE STANDARD
Tolerance
–0.022
–0.126
Tolerance
Shaft
Hole
–0.030
+0.046
–0.076
+0
PC200/220(LC)-7
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