Gun drills operate at relatively high cutting speeds with low feeds per revolution. Approximate starting values are shown in the charts on this page.
Feed rates are critical to chip formation. The values shown here may need to be adjusted for optimum results.
Reliable chip evacuation and good surface finish can only be ensured if sufficient coolant volume and pressure are available.
GUNDRILL WHIP MOMENT
To establish the maximum length to diameter ratio of an
unsupported drill for any given surface speed, trace the surface speed to the
intersection of the curve and read off the L/D ratio on the vertical scale.
Example:
Using a gun drill at 100 metres/min, the L/D ratio is 55:1
therefore for a dia. 10,0 gun drill the maximum unsupported shank length is
550mm.