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Explore the World of Soft…e: Engineering & Science
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DRILLING.TXT
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1994-11-01
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Drilling often is a greater problem with stainless steel than in carbon
or alloy steel, mainly because stainless steel is more easily work
hardened. When a spot is severely work hardened, it will cause the
drill to wander or overheat thus dulling the drill in a few revolutions.
When conventional center punches are used, they must be tapped lightly
(especially when the higher-nickel grades of stainless are being drilled
to avoid creating hard spots. Triple punches are preferred because they
are less likely to cause work hardening in the center. The use of drill
templates is another means of avoiding work hardening. When starting or
re-entering the hole, the drill should be at full speed with positive
feed. Dwell periods should not be permitted.
When numerically controlled equipment is available, center drilling is
often used for locating and starting holes. The two examples that follow
describe operations in which certain drilling and the use of numerically
controlled machines eliminated the need for drill jigs. In some
applications, the use of spiral point drills has eliminated the need for
jigs or center drilling when numerical control is used on the machine.
=========================================================================
Nominal Speeds and Feeds for Drilling Stainless Steels
with High Speed Steel Drills Type of Condi- Brinell
Speed Feed(ipr) for nominal diam.(in.) of: steel(a) tion(b) hardness
(sfm)
.125 .250 .500 .750 1.000 1.500 2.000 FM Fer Ann 135 to 185
140 .003 .005 .010 .014 .018 .020 .025 FM Mar Ann 135 to 185
140 .003 .005 .010 .014 .018 .020 .025 Ann/CD 185 to 240
130 .003 .005 .010 .014 .018 .020 .025 Q/T 275 to 325
65 .002 .004 .006 .008 .010 .014 .018 Q/T 375 to 425
40 .001 .002 .004 .006 .008 .009 .010 FM Aus Ann 135 to 185
100 .003 .005 .010 .014 .018 .020 .025 CD 225 to 275
90 .003 .005 .010 .014 .018 .020 .025 Ferritic Ann 135 to 185
60 .002 .003 .006 .008 .010 .014 .018 Mar(410) Ann 135 to 185
70 .003 .004 .006 .008 .010 .014 .018 Ann 175 to 225
60 .002 .003 .006 .008 .011 .014 .018 Q/T 275 to 325
50 .002 .003 .005 .008 .011 .013 .016 Q/T 375 to 425
40 .001 .002 .004 .006 .008 .009 .010 Mar(431) Ann 225 to 275
50 .002 .003 .005 .008 .011 .013 .016 Q/T 275 to 325
45 .002 .003 .005 .008 .011 .013 .016 Q/T 375 to 425
40 .001 .002 .004 .006 .008 .009 .010 Mar(440) Ann 225 to 275
40 .002 .003 .005 .009 .010 .012 .013 Q/T 275 to 325
35 .001 .002 .003 .005 .006 .008 .009 Q/T 375 to 425
25 .001 .002 .003 .004 .005 .006 .007 Q/T Rc48 to 52
20 .0005 .001 .002 .002 .003 .003 .004 Aus(304) Ann 135 to 185
50 .002 .003 .005 .009 .010 .013 .016 CD 225 to 275
45 .002 .003 .005 .008 .011 .013 .016 Aus(316) Ann 135 to 185
45 .002 .003 .005 .008 .011 .013 .016
Abbreviations used: FM = Free machining Fer = Ferritic
Mar = Martensitic Aus = Austenitic Ann = Annealed
CD = Cold drawn Q/T = Quenched and tempered Hard = Hardened
N/T = Normalized and tempered
SFM = Surface feet per minute IPR = Inches per revolutiom