アルミニウム板の皿穴あけに関する研究 (第1報)

皿穴の形状とのみ刃角の関係

抄録

When aluminium sheet is countersunk with a twist drill, it is well known that it is not easy to obtain a circular countersink but an odd numbered polygonal holes, such as the rounded triangular, pentagonal or heptagonal hole. It is due to so-called "the walking phenomenon of drill" which gets into trouble not to be neglected in practice from the viewpoint of machining accuracy, finished appearance and others.
In this paper, the influence of chisel edge angle of drill on the geometry of countersink is examined and the drilling conditions to obtain the circular hole are searched in the case of countersinking sixsorts of aluminium sheets, e. g., 2S-H, 3S-H, 14S-O, 52S-H, 61S-H and G4-H.
As the results, chisel edge angle was found to heve a large affect on increasing "the out of roundness". And the latter In the case of using high-tension hard alloy, such as, 52S-H and G4-H, the countersink is enarly circular and has smallusing roundness, even if the chisel edge angle is considerablly large (in this experiment, 140°), however, in the case of low-tension soft alloy, such as, 2S-H and 3S-H, the countersink has small out of roundness, unless the chisel edge angle is small (in this experiment, not more than 120°).
This study was conducted uuder the partial financial support of the fund furnished by Scholarship Committee of the Institute of Light Metals for which we feel deeply grateful.