Jet J-2221VS, Operating Instructions And Parts Manual

Page: 14 / 32

14
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.
Feeds for Drilling
The feed of a drill is governed by the size of the
tool and the material drilled. Because the feed
rate partially determines the rate of production
and also is a factor in tool life, it should be
chosen carefully for each job. In general, the
most effective feeds will be found in the
following ranges:
Diameter of Drill Feed per Revolution
(inches) (inches)
Under 1/8 ....................0.001 to 0.002
1/8 to 1/4 .....................0.002 to 0.004
1/4 to 1/2 .....................0.004 to 0.007
1/2 to 5/8 .....................0.007 to 0.015
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 corners
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.
Speeds for High Speed Steel Drills
Speed
Material In
SFPM
Alloy Steel — 300 to 400 Brinell ................ 20 - 30
Stainless Steel......................................... 30 - 40
Automotive Steel Forgings ....................... 40 - 50
Tool Steel, 1.2C ....................................... 50 - 60
Steel, .4C to .5C ...................................... 70 - 80
Mild Machinery Steel, .2C to .3C ............. 80 - 110
Hard Chilled Cast Iron .............................. 30 - 40
Medium Hard Cast Iron .......................... 70 - 100
Soft Cast Iron ...................................... 100 - 150
Malleable Iron.......................................... 80 - 90
High Nickel Steel or Monel ....................... 40 - 50
High Tensile Bronze................................ 70 -150
Ordinary Brass and Bronze .................. 200 - 300
Aluminum and its Alloys ....................... 200 - 300
Magnesium and its Alloys ..................... 250 - 400
Slate, Marble, and Stone ...........................15 -25
Plastics and similar material (Bakelite) .. 100 - 150
Wood ................................................... 300 -400
Titanium Alloys ........................................ 10 - 25
Titanium Alloy Sheet ................................ 50 - 60
In cases where carbon steel drills are applicable,
the drill should be run at speeds of from 40 to 50
percent of those given above.