Starting the drill is often a greater problem in drilling 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.
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            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 or 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   Rc 48 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 and T = Quenched and tempered
    Hard = Hardened      N and T = Normalized and tempered.