Baileigh DP-1512B, Operating Instructions Manual

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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:
1. Composition and hardness of material.
2. Depth of the hole.
3. Efficiency of the cutting fluid.
4. Type and condition of the drilling machine.
5. Desired quality of the hole.
6. Difficulty of set-up.
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.