Abstract
Continuing the previous report, the influences of the point angle and the lip clearance of twist drill on the figure of counter-sink are examined in the case of six sorts of aluminium sheet, e. g. 2S-H, 3S-H, 14S-O, 52S-H, 61S-H and G4-H.
As the results, it turns out that the figure and the out of roundness of counter-sink are affected largely by the point angle and the lip clearance: that is, the smaller the point angle and the lip clearance respectively are, the more similar to circle the figure of counter-sink is, and the smaller the point angle and the lip clearance respectively are, the smaller the out of roundness of counter-sink is. In the case of the counter-sinking of the soft materials as like 2S-H, 3S-H or so, it must be used smaller point angle drill or smaller lip clearance drill to obtain the figure which is simillar to circle and has less out of roundness than in the case of the hard materials as like 52S-H, G4-H or so.
This study was conducted with funds furnished by Scholarship Committee of the Institute of Light Metal Foundation, for which we feel deeply grateful.
