WAVEGUIDE FOR MICROWAVE

PURPOSE:To improve the detecting performance of a detector or the like utilizing a microwave and to miniaturize the inner size of the waveguide by forming a metallic coating film at the peripheral of a path of a microwave made of a synthetic resin. CONSTITUTION:The waveguide 8 is formed by forming a metallic coating film 10 around a synthetic resin made plate 9 transmitting a microwave. The film 10 is formed by plating or vapor-deposition or the like. Plural waveguides 8 are fixed overlappingly to surround the tip of a drill 2 at the lower end of a block 11 arranged slidably in the axial direction of a spindle 1 to cover the tip of the spindle 1. Thus, the presence of the drill 2 is detected at each waveguide 8 and a defect of the tip of the drill 2 is detected. Further, in regard to the thickness of the waveguide 8, since the thickness of the synthetic resin plate 9 is made thin, the inner size of the waveguide 8 is miniaturized.