Tool position offsetting system for a spare tool

A tool position offsetting system comprising:

• a numerically controlled machine tool having a tool spindle for inserting a tool therein;
• a numerical controller connected to said machine tool for controlling machining operations of said machine tool;
• a memory provided in said numerical controller for storing tool offset data for said tool;
• said numerical controller being capable of offsetting the tool position of said tool in accordance with said tool offset data;
• tool life detecting means connected to said numerical controller for detecting the end of the useful tool life of said tool and based thereon to output a first signal;
• spare tool changing means connected to said numerical controller and said tool life detecting means for replacing said tool by a spare tool so as to insert said spare tool in said tool spindle in response to said first signal, said spare tool being the same type as the replaced tool;
• dimensional data setting means connected between said spare tool changing means and said numerical controller for setting the dimensional data for said spare tool, said dimensional data corresponding to the dimensional difference between said replaced tool and said spare tool;
• spare tool detecting means connected to said spare tool changing means for detecting whether a tool inserted in said tool spindle is said spare tool to output a second signal;
• input controlling means connected between said spare tool detecting means and said numerical controller for effecting the introduction of the dimensional data for said spare tool to said memory in response to said second signal thereby to amend said tool offset data stored in said memory, whereby said numerical controller controls the machining operations in accordance with said amended tool offset data.