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9. Use the feed handle to feed the drill into the material. Use a smooth steady motion with
enough force to allow the drill to cut. It may be necessary to raise the drill from time to time
to allow the flutes to clear the material.
10. At the end of a drilling operation, press the stop button to turn
OFF
the machine.
Chip Characteristics
If chips produced by your operation are blue and burnt and overheated, but the cutting speed is
correct, reduce the feed rate until the chips are silver. If the chips are powdery, increase the
feed rate so the chips are coarser but not overheated.
Indication of Extreme Speeds and Feeds
A drill that splits up the web is evidence of too much feed or insufficient tip clearance at the
center as a result of improper grinding. The rapid wearing away of the extreme outer comers of
the cutting edges indicates that the speed is too high. A drill chipping or braking out at the
cutting edges indicates that either the feed is too heavy, or the drill has been ground with too
much tip clearance.
DRILLING RECOMMENDATIONS
Speeds for Drilling
The speed of a drill is usually measured in terms of the rate at which the outer periphery of the
tool moves in relation to the work being drilled. The common term for this is Surface Feet per
Minute (SFM). The relationship of SFM is expressed in the following formulas:
SFM = 0.26 X rpm X Drill Diameter (in inches)
RPM = 3.8 x {SFM/Drill diameter [in inches]}
In general, the higher the speed the shorter the drill life. Operating at the low end of the speed
range for a particular material will result in longer life. The most efficient speed for operating a
drill depends on many variables:
•
Composition and hardness of material.
•
Depth of the hole.
•
Type and condition of the drilling machine.
•
Desired quality of the hole.
•
Difficulty of set-up.
