The feed of a drill is the rate of penetration into
and whether or not a cutting fluid is used. The
the work for each revolution. Feed is expressed in
following cutting speeds are recommended for
thousandths of an inch per revolution. In general, the
high-speed steel twist drills. Carbon steel drills
should be run at one-half these speeds, while carbide
larger the drill, the heavier the feed you may use.
may be run at two to three times these speeds. As you
Always decrease feed pressure as the drill breaks
gain experience, you will be able to vary the speeds to
through the bottom of the work to prevent drill
breakage and rough edges. The rate of feed depends
suit the job you are doing.
on the size of the drill, the material you are drilling,
Low carbon steel . . . . . . . . . 80-110 fpm
and the rigidity of the setup.
Medium carbon steel . . . . . . . 70-80 fpm
Use the following feed rates, given in thousandths
of an inch per revolution (ipr), as a general guide until
Alloy steel . . . . . . . . . . . . .
50-70 fpm
your experience allows you to determine the most
Corrosion-resistant steel
efficient feed rate for each different job.
(stainless) . . . . . . . . . . . 30-40 fpm
200-300 fpm
Brass. . . . . . . . . . . . . . . .
IPR
Drill Diameter
Bronze . . . . . . . . . . . . . . .
200-300 fpm
Monel . . . . . . . . . . . . . . .
40-50 fpm
No. 80 to 1/8 inch
0.001-0.002
1/8 inch to 1/4 inch
0.002-0.004
Aluminum . . . . . . . . . . . . .
200-300 fpm
1/4 inch to 1/2 inch
0.004-0.007
Cast iron . . . . . . . . . . . . . .
70-150 fpm
1/2 inch to 1 inch
The speed of the drill press is given in rpm. Your
0.007-0.015
shop will usually have tables giving the proper rpm at
Greater than 1 inch
0.015-0.025
which to run a drill press for a particular metal or you
may find them in machinists' handbooks. You can use
a formula to determine the rpm required to give a
Use the lower feed rate given for each range of drill
specific rate of speed in fpm for a specific size drill.
sizes for the harder materials such as tool steel,
For example, if you wish to drill a hole 1 inch in
corrosion-resistant steel and alloy steel. Use the
diameter at the speed of 50 fpm, you would compute
higher feed rate for brass, bronze, aluminum, and
the rpm as follows:
other soft metals.
fpm 12
It is usually necessary to use a cutting oil or coolant
rpm =
š D
to drill carbon steel, alloy steel, corrosion-resistant
steel and certain nonferrous metals such as Monel.
50 12
For most drilling operations, you can use soluble oil
=
3.1415 1
or a synthetic coolant. You may drill aluminum,
brass, cast iron, bronze and similarly soft metals dry
unless you use a high drilling speed and feed.
= 36140 6
0
. 1
Holding the Work
= 190
Before drilling, be sure your work is well
where
clamped down. On a sensitive drill press you will
probably have to use a drill vise and center the work
by hand. Because the work done on this drill press is
fpm = required speed in feet per minute
comparatively light, the weight of the vise is
sufficient to hold the work in place.
š = 3.1416
The larger drill presses have slotted tables upon
12 = constant
which you may bolt or clamp work of considerable
weight. Use T-bolts, which fit into the T-slots on the
D = diameter of drillin inches
table, to secure the work. You can also use various
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