JPH0253184B

PCT No. PCT/JP83/00330 Sec. 371 Date May 17, 1984 Sec. 102(e) Date May 17, 1984 PCT Filed Oct. 6, 1983 PCT Pub. No. WO84/01534 PCT Pub. Date Apr. 26, 1984.A tool life supervision method in which the life of a tool is monitored and machining is performed by using another tool when a former tool has reached the end of its life. The tool life supervision method includes the steps of setting in memory means a number of parts to be machined, which number conforms to tool life; setting in the memory means a tool selection number correction value Nct; inserting at an end of an NC machining program at least an instruction or symbol which indicates the end of the program; counting instructions or symbols indicating the end of a program; monitoring whether a counted value coincides with the preset number of parts to be machined and counting the number of times coincidence is achieved; performing the following operation using an arithmetic circuit 110: Nt+Nctxn wherein n represents the number of times coincidence is achieved, Nt represents a tool selection number indicated by a tool selection instruction in the NC machining program, and Nct represents a tool selection number correction value, and selecting a tool by employing the result of the aforesaid operation as an actual tool selection number.