| 摘要 |
PROBLEM TO BE SOLVED: To provide a means for reducing breakage of a drill by continuously exhibiting satisfactory lubricating operation of a lubricating layer disposed on an entry board, improving the positional accuracy of a bore, and avoiding stains of a workpiece due to dripping of lubricating ingredients in small-bore diameter drilling. SOLUTION: The lubricating layer 4 formed on at least one surface of an aluminum-made board 2 is composed of a mixed composition containing polyethylene glycol having a number average molecular weight equal to or higher than 100 and under 1000, polyethylene glycol having a number average molecular weight equal to or higher than 10000, propylene glycol ester alginate and trimethylol propane. COPYRIGHT: (C)2006,JPO&NCIPI
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