Tool and its finishing method of surface for center fin member of air conditioning apparatus for vehicle

A method for finishing a surface of fin blades of a tool for an air conditioning apparatus, the tool including a plurality of fin blades each having a circular cutter shape and being provided at a periphery thereof with a plurality of cutting teeth and at a central portion thereof with a central hole, the fin blades being stacked on one another in such a fashion that the central holes are aligned together, and a pair of jig discs arranged at opposite sides of the stacked fin blades, respectively, in such a fashion that the jig discs are arranged in a coaxial and integral fashion with the fin blades, the tool serving to form louvered center fins having a plurality of continued flat wall portions formed by bending a thin strip in a desired pitch in a zig-zag fashion, each of the flat wall portions having a plurality of louvers, the method comprising the steps of:

• plasma nitrifying only a crest portion of the cutting teeth in each of the fin blades to a depth of 20 to 60 μm thereby forming a nitride layer on each of the crests;
• and
• depositing a coating of TiC, TiN or TiCN to a thickness of not more than 2 μm over the nitride layer in accordance with a plasma chemical vapor deposition method or a plasma physical vapor deposition method.
• 14.The method according to claim 13, wherein the step of plasma nitrifying the crests is carried out by fitting the fin blades around a central shaft included in a jig in such a fashion that the fin blades are stacked on one another without any space between adjacent ones thereof, and then loading the fin blades mounted to the jig in a nitrifying furnace.