Komatsu PC500LC-10R, Shop Manual, Page: 62 / 758

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 clear-
ance.
• When some parts are repaired, the clearance is generally
adjusted to the standard clearance.
• The values indicating performance and function of new
products or equivalent are called "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.
Standard interference
• When the diameter of a hole of a part shown in the given standard dimension and tolerance table is smaller
than that of the shaft to be inserted, the difference between those diameters is called "interference".
• Subtract the maximum dimension of the hole from the minimum dimension of the shaft and call it (A). Sub-
tract the minimum dimension of the hole from the maximum dimension of the shaft and call it (B). The range
between (A) and (B) is "standard interference".
• After repairing or replacing some parts, measure the dimension of their hole and shaft and check that the
interference is in the standard range.
Repair limit and allowable value or allowable dimension
• The dimension of parts changes due to the wear or deformation while they are used. When the dimension
changes exceeding certain value, parts cannot be used any longer. This value is called "repair limit".
• If a part is worn to the repair limit, it must be replaced or repaired.
• The performance and function of products lower while they are used. A value with which the product can be
used without causing a problem is called "allowable value" or "allowable dimension".
• A product whose dimension is out of the allowable value, must be repaired. However, since the allowable
values are generally estimated through various tests or experiences in most cases, the judgment must be
made in consideration of the operating condition and customer's requirement.
Allowable clearance
• Parts can be used until the clearance between them is increased to a certain limit. The limit at which those
parts cannot be used is called "allowable clearance".
• If the clearance between the parts exceeds the allowable clearance, they must be replaced or repaired.
Allowable interference
• The allowable maximum interference between the hole of a part and the shaft of another part to be assem-
bled is called "allowable interference".
• The allowable interference shows the repair limit of the part of smaller tolerance.
EXPLANATION OF TERMS FOR MAINTENANCE STANDARD 00 INDEX AND FOREWORD
00-60 PC500LC-10R