Steep Flutes For Chip Ejection

Drill photos courtesy Guhring.

A challenge in high speed drilling is to prevent hot chips from adhering to the tool. One approach is to use high-pressure, through-tool coolant to flush hot chips from the hole. Using high-pressure coolant effectively may call for a change in drill design.

Steeper flutes may be in order. A steeper flute gives the chip a more direct escape route.

For carbide tools suited to through-tool coolant, experiment with flute spirals of 15 degrees or less. In cast iron, good results have been achieved with a 0 degree spiral (straight flutes).

Without coolant, the conventional spiral may still apply. Flutes at lower speeds wedge the chip up out of the hole . . . and in high speed dry drilling, it may be possible to preserve this mechanism with a low-friction coating.