I am working on a project and will have to drill 8 holes in 8-18
stainless steel. The stock is 3/16" thick. I have good equipment ..
drill press, machinist vise, sharp drill bits, etc. The holes will be
13/32" in size.
Shall I drill in one step or start with a pilot hole and enlarge. If
the latter, what drill sizes should I use?
All suggestions appreciated.
Consider buying a step drill, Unibit is one brand name. Start with a pilot
hole, 1/8"-3/16" or so. Sharp, (new), drill bit, lots of pressure and slow
speed. Stainless work hardens so if you use a dull bit, you may never get a
hole drilled in that spot.
HSS is OK to use. Start with a center drill if you have one, or a split
point drill about 3/16" . If using a drill bit, start by pecking the
material until you get it started. Use a speed of approx. 950 rpm.( cutting
speed times four divided by the drill diameter ). Then you can go to the
13/32 drill bit and use approx 500 rpm. If your drill is sharp the burr
will be minimal as long as you don't let the material get hot. Be sure to
use a cutting oil, it will make things alot easier.
I would make certain to use a good entry material, well clamped to the
stainless steel. This way the burrs will be on the entry and not on the
finished product. As far as what material to use for this....just pick
something close in hardness to stainless and maybe 1/8" thick or so....Make
a few test holes in scrap if you aren't comfortable with the setup....good
THANKS to all who replied. I have a new set of titanium nitride
coated HSS drill bits. I used a 3/16 and 13/32 with plenty of coolant
and a slow speed. EASY !!! The stainless was type 303 and not very
Having a heavy duty drill press (30 year old Rockwell) and a good vise
helped. My drill bits seem to have tolerated the drilling quite well
and remain sharp.
FYI: I got the bits from Harbor Freight. Over the years I have found
that their drill bits and "good" screwdrivers are as good or better
than my USA stuff (I do have a set of SnapOn screwdrivers for
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