Table of Contents
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FOREWORD
12
EXPLANATION OF MAINTENANCE STANDARD TERMS
•
The maintenance standard values necessary for judgment of
products and parts are described by the following terms.
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 temporary standard size
is set and an allowable difference 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
"tolerance".
•
The tolerance with the symbols of + or – is indicated 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 tolerances 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
2.
Standard Clearance And Standard Value
•
The clearance made when new parts are assembled is called the "standard clearance", which is indicated by the range
from the minimum clearance to the maximum clearance.
•
When some parts are repaired, the clearance is generally adjusted to the standard clearance.
•
A value of performance and function of new products or equivalent is called the "standard value", which is indicated
by a range or a target value.
•
When some parts are repaired, the value of performance/function is set to the standard value.
3.
Standard Interference
•
When the size of a hole is smaller than the size of a shaft because of the standard size and tolerance, the difference
between these sizes is called the "interference".
•
The range (A – B) from the difference (A) between the minimum size of the shaft and the maximum size of the shaft
to the difference (B) between the maximum size of the shaft and the minimum size of the hole is the "standard
interference".
•
After repairing or replacing some parts, measure the size of their hole and shaft and check that the interference is in
the standard range.
00-20
b
EXPLANATION OF MAINTENANCE STANDARD TERMS
Tolerance
-0.022
-0.126
Tolerance
Shaft
Hole
–0.030
+0.046
–0.076
+0
00
PC200/220LL-8
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