| 摘要 |
PURPOSE:To increase life by composing a single layer or the innermost layer from tungsten carbide in a surface coated cemented carbide drill having a tip surface coated with one or more layers of which thickness amounts to 0.1-10mu. CONSTITUTION:For example, each 1mu thickness of various hard materials is coated by a high frequency magnetron spattering equipment to a cemented carbide small size stepped twist drill of 0.95mm as a base material and 3 pieces of glass epoxy printed circuit boards are laminated and subjected to drilling test at a cutting speed of 208m/min with a feed rate of 0.05mm/rev. to drill a hole of 0.95mm dia. and 4.8mm depth with a result that a drill coated with WC has the longest life and a coated film thickness of 0.1-10mu is effective. Thus, the drill can make a hole through a laminated printed circuit board effectively with long life.
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