14, the left nose R center c0 of the cutting tool 11 is moved along the first path 18 of (a-P0-P12-b-c), then the second path 18 of (c-P0-d-P10-P11-P12-P0), and finally the third path 18 of (P0-P1-P3-P4-P5
When θs≦θ and θe≦θ, or when θs>θ and θe>θ, similarly as in the cases of the straight lines shown in FIGS. 19 and 20, an offset configuration (P0-P1-P2) 17 is obtained.
