Limits for Wear

The four dimensions, typically covered in wear tables are:

• Dimension New: It relates to the size of the part when new and will show the relevant tolerances.
• Permissible Worn Dimension: It refers to the size to which a part may wear before it must be rejected as unserviceable. Parts, which are not worn beyond this size can be used again, providing a suitable mating part is chosen to keep the clearance within the permissible figure. This will frequently involve choosing a new part to mate with the worn part.
• Clearance New: It is the desired clearance in limit form. Interference fits are quoted as negative clearances.
• Permissible Worn Clearance: It refers to the maximum allowable clearance when reassembling the component.