Drilling Stainless Steel

From:  gweaver [SMTP:gweaver-at-earthlink-dot-net]
Sent:  Friday, May 29, 1998 10:57 PM
To:  Tesla List
Subject:  Re: Drilling Stainless Steel

Also try drilling the 1st hold with a 1/8" diameter drill bit at about 200
RPM's using some good quality cutting oil for cooling.  I have found by
drilling a small pilot hole first makes it much easier to drill a larger
hole later.  If the metal turns blue its getting too hot.  And when the
metal over heats it gets harder and very tough to drill.  The stainless your
trying to drill is going to be work hardened all ready because salad bowl
are a made in a drawing press which compresses and stretches the molecules
of the stainless steel.  Drilling the 1st hole with a small drill bit will
make the job much easier but your will still probably have to hand sharpen
your drill bit after each hole.  You can hand sharpen your drill bits on a
bench grinder.  If you don't know how to hand sharpen drill bits then buy
them in a package of 10 from a local industrial tool supply company.  Drill
bits from the local industrial supply company are much higher quality and
cost a lot less than the drill bits you get at the hardware store or Wal
Mart.  I buy drill bits at work and the 1/8" diameter high speed steel bits
cost me 23 cents each for a pack of 10.  Don't buy coated drill bits, they
will just cost more and won't help you very much here anyway.  You need
enough pressure pushing down on the drill bit to make it cut and not more.
You should be able to hand drill the stainless with a 1/8" drill bit.
Pounds per square inch pressure on the drill bit tip is what you need to
think about.  After you drill the 1/8" hole increase the drill bit size to a
larger diameter but remember not to get a diameter so large you can't push
hard enough by hand to make it drill.  If you drill the 2nd hold 1/4" you
should be able to push hard enough to make it drill.  If you try and drill
the 2nd hole 3/8" you will have to push much harder than you would if you
drill the 2nd hole 1/4".  Increase the drill bit size untill you get the
hole the diameter you need.  Salad bowls are thin metal and will over heat
very easy so take is slow.

Gary Weaver

>The problem is that stainless steel work-hardens VERY easily. This means
>that IF you let the drill bit rotate at the hole without cutting metal
>(ie. not enough force to cut), the metal will be very difficult to be
>cut/drilled again. So PUSH as hard as you can on the drill and use the
>correct RPM. It does help considerably to add cutting oil (or coolant) as
>it will both help the drill cutting edge (forms a film there) and cool the
>system. Use a drill with correct cutting angles as well, if possible. 
>That is for the "usual" austenitic stainless steels (aisi316 etc.). 
>Special alloys can be next-to-impossible to cut especially after they 
>have been heat-treated.. But I think the bowls are the cheapest
>alloy they could use so it should not be too hard to drill.
>  Kristian Ukkonen.

Try drilling at a slow speed, (100 to 200 rpm), with a drill press using
steady pressure. Also use high carbon bits and keep them cool with light
oil. Another good point is to clamp the part you are drilling. If you
hold the part steady, the hole will be round.

Hope this helps!