Explanation Of Terms For Maintenance Standard - Komatsu PC200-8M0 Shop Manual

200 Foreword and general information

Explanation of terms for maintenance standard

Explanation of terms for maintenance standard

q The chapter of maintenance standard shows judgement criteria to determine the products to be
replaced or to be reused. The judgement criteria are described by using the following terms.
Standard dimension and tolerance
q To be accurate, the finished dimension of a
part is slightly different from one to another.
To specify the finished dimension of a part, a
q
certain dimension is set for the part and an
allowable difference from that dimension is
indicated.
q The above dimension set is called the "stan-
dard dimension" and the range of difference
from the standard dimension is called the "tol-
erance".
q The standard dimension and tolerance are
indicated by attaching the symbols of + or -
and a number on the right side of the standard
dimension.
Example:
Standard dimension
120
q The tolerance may be indicated in the text and
a table as "standard dimension (upper limit of
tolerance/lower limit of tolerance)."
Example: 120(-0.022/-0.126)
Usually, the dimension of a hole and the
q
dimension of a shaft to be inserted into the
hole are indicated by the same standard
dimension and different tolerances of the hole
and shaft. The tightness of fit is decided by the
tolerance.
q Indication of dimension of rotating shaft and
hole and their related drawing.
Example:
Standard
dimension
60
Standard clearance and standard value
q The clearance made when new parts are
assembled is called the standard clearance,
which is indicated by the range from the mini-
mum clearance to the maximum clearance.
q When some parts are repaired, the clearance
is generally adjusted to the standard clear-
ance.
q The values indicating performance and func-
tion of new products or equivalent are called
the "standard value", which is indicated by a
range or a target value.
PC200, 200LC, 220, 220LC-8M0
Tolerance
–0.022
–0.126
Tolerance
Shaft Hole
–0.030 +0.046
–0.076 +0
q When some parts are repaired, the value of
performance/function is set to the standard
value.
Standard interference
When the diameter of a hole of a part shown in
q
the given standard dimension and tolerance
table is smaller than that of the shaft to be
inserted, the difference between those diame-
ters is called the "interference".
q Subtract the maximum dimension of the hole
from the minimum dimension of the shaft and
call it (A). Subtract the minimum dimension of
the hole from the maximum dimension of the
shaft and call it (B). The range between (A)
and (B) is the "standard interference".
q After repairing or replacing some parts, mea-
sure the dimension of their hole and shaft and
check that the interference is in the standard
range.
SEN06112-00
1
11
00-200