Quick-helix drills

Figure 7.13. (a) Standard, (b) slow, and (c) quick helix drills... 

Quick-helix drills, with a helix angle of 40° and a point angle of 100°, are suitable for drilling the softer materials such as aluminium alloys and copper. Fig. 7.13(c). 

Drills are available with parabolic flutes where the heel of the flutes is rolled over, which provides additional flute space for chip evacuation and produces a thinner land. This is advantageous particularly with deep hole drilling on CNC machines where constant withdrawl of the tool to clear chips can be minimised thus reducing cycle times. They have a 130° point angle and a quick helix around 38°. These are available with a nitride coating to increase wear resistance and improve tool life. 

These special drills usually have one or two highly polished or chrome plated flutes, narrow lands, and large helix angles to quickly expel chips and minimize frictional heating. 

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