A basic spiral operation of a tool is controlled by storing, in a controller, an automatic operation program of a threading cycle which regulates the basic spiral operation of the tool corresponding to a thread shape by specifying a spindle revolving speed RC, a thread lead ZR and a thread cutting finish point Z2 or the like. A depth of cut by the tool is determined by an operator who operates a handle of a manual pulse generator (73) to cut the work and confirms the cutting conditions. IMAGE
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