00 Index and foreword SEN00056-01 2. Standard clearance and standard value 5. Clearance limit q The clearance made when new parts are assembled is called the “standard clear- ance“, which is indicated by the range from the minimum clearance to the maxi- mum clearance. q 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 the “clearance limit”. q If the clearance between the parts exceeds the clearance limit, they must be replaced or repaired. q When some parts are repaired, the clear- ance is generally adjusted to the standard clearance.
q 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. 6. Interference limit q The allowable maximum interference between the hole of a part and the shaft of another part to be assembled is called the “interference limit”. q When some parts are repaired, the value of performance/function is set to the stan- dard value. q The interference limit shows the repair limit of the part of smaller tolerance. q If the interference between the parts exceeds the interference limit, they must be replaced or repaired. 3.
Standard interference q 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”. q The range (A – B) from the difference (A) between the minimum size of the shaft and the maximum size of the hole to the difference (B) between the maximum size of the shaft and the minimum size of the hole is the “standard interference”. q After repairing or replacing some parts, measure the size of their hole and shaft and check that the interference is in the standard range. 4. Repair limit and allowable value q The size of a part changes because of wear and deformation while it is used.
The limit of changed size is called the “repair limit”. q If a part is worn to the repair limit must be replaced or repaired. q The performance and function of a prod- uct lowers while it is used. A value below which the product can be used without causing a problem is called the “allowable value”. q If a product is worn to the allowable value, it must be checked or repaired. Since the permissible value is estimated from vari- ous tests or experiences in most cases, however, it must be judged after consider- ing the operating condition and customer's requirement. D65EX, PX, WX-15E0 9