Small diameter spiral drill - has largest groove angle at drill point, preferably 35 degrees, lowest at lower end

摘要

Spiral drill, for drilling soft material with an encasement and grooved shaft with spirally wound swarf removing grooves extending to the drill point. The spiral angle of the grooves (12, 14) has its largest value at the drill point and then over the length of the grooved shaft (10) alters constantly until it achieves its lowest value at the lower shaft end. The spiral angle of the groove (12, 14) at the drill point is preferably 35 deg. whilst at the lower end the preferred angle is 10 deg.. The width of the grooves (12, 14) constantly increase in the direction of its rear end. The drill is made of hard metal and is suitable for drilling holes of 2mm diameter or less.