By any chance can someone post a picture of what a split pointed
drill bit looks like?
Thanks,
Margaret
http://www.mmsonline.com/article.aspx?id=14722
this a link to a article on sharpening drill bits for different
metals.
Thanks Randy
AKA Enjen Joes
I’m going to assume that you know that this is Stainless Steel, and
that is would be a commonly used grade of stainless steel, such as
300 series stainless steel?? If its hardened 17-4, or 400 series
then this may not helpful depending of how hard your
stainless is ??? If it is hardened grade of stainless, then you will
need either cobalt, or a carbidedrill. Depending on how hard it is??
For all I know this material maybe chrome plated brass? 
So lets just say its 300 series stainless. From what I’ve read here
on your posting… I will guess that your material may have been
work hardened due to dwelling a carbide drill on the surface of your
project? If your project is 300 series stainless steel, that has been
work hardened… you may also have bits of that carbide drill fused,
and imbedded into the start of what was supposed to be a drilled
hole?? I know it been said here already, but… using a solid
carbide drill in a hand drill would be a big “no no” Carbide drills
are very brittle, and require controlled solid cutting conditions in
order to gain any benefit from their use.
If you still want to get a hole in your project. It will help quite
a bit if you grind away the problem area with a diamond burr. (Wear
your safety goggles, and dust mask) Carbide, and diamond dust is
hazardous for your eyes and lungs.
Try to grind threw the problem area, with out creating to much heat.
(use a dab of water now and then to keep it cool. Peck slowly at the
damaged surface without dwelling the burr if possible. At the same
time try to grind a funnel shaped depression as you remove the
hardened material. This will give your drill a spot mark, when you
start drilling again.
Drilling two 1/8 deep x 1/8 dia. holes in 300 series stainless steel,
“un-hardened” 17-4 or 400 series stainless. This should not be to
difficult of a task… Your local hardware stores “High Speed Steel
Drills” bits will do just fine. Remember its only 2 holes. HSS is a
good cheap choice for drilling short quantity holes is un-hardened
steels. A more expensive choice, but better drill would be a TIN
coated cobalt 135 degree spilt point drill. They are harder, and
their for more brittle than HSS. If you want drill 2000 to 4000 holes
in 300 series stainless steel a TIN or TiAlN coated, coolant through,
140 degree solid carbide SE pointed drill. Like a hot knife threw
butter, it will run all day and all night. Thatcs a very expense
choice, and would not recommend it for this project. Personally I
would go with whatcs cheap and available… so the HSS drill from
your local hardware store will work fine.
If at all possible use a drill press, and not a hand drill. You need
a little more control over the drilling process. I’m not saying you
canct use a hand dill, you just will have much better results with a
drill press. Ether way you will better results by adding a another
piece of metal behind your project to drill into. This will give you
a very clean exit hole, and you wonct go flying when the drill exits
your project. Clamp the part with its backing material securely to
the table of your drill press, precisely aligning the "spot mark"
with the tip of your drill. If you have a #2 or #3 center drill now
would be a good time to place it in the chuck. If you Don’t have a
center drill, set your drill into the drill chuck instead. If you
have an adjustable stop, set it accordingly, so you Don’t drill
trough your part and into your table. If you have the ability to set
your spindle speed. Set it for about (25 - 30 surface feet per
minute) thatcs about 850 rpm for a 1/8 hole. For those that may be
interested in the maththatcs ((30 sfm x 12) / (.125 x 3.14)) = 916
RPM.
Since your most likely do not have a flood coolant system, and Don’t
have cutting oil around. I recommend using some vegetable oil from
yo= ur kitchen. Your only drilling 2 holes, so your not really too
worried about tool life here. You just want a little lubrication,
and cooling action. Find a small plumbers acid brush, (or likeness
there off) and place small cup / can of your oil close to your work.
You need to dab plenty of oil as your drilling so keep it close.
Just to explain the problem that may be at hand here a little more…
If you have a part with a work hardened surface, your goal is to push
that drill tip “threw” the problem surface area, and cut the soft
material below the surface. We Don’t want our drills cutting edge
dwelling around on the surface, trying to cut any remaining carbide,
and or heat treated material that may be on that surface. So we want
to break threw that surface, as quickly as we can to cut the soft
material thatcs hopefully under neath all that surface junk. Think
about the type of a cut your going take on your first drill peck for
a moment… A good steady push threw, that wil cut in below and into
that softer material, then pull back out of the cut…ok? One more
thing to remember, if that material is still too hard… Your drill
press may just bind and stop. Your drill may melt and become one with
your work, or your drill may bind, twist and snap, throwing shards of
metal threw the air at high speed. A Face Shield, or Safety Glasscs
with a make shift shield would be a wise choice. If you Don’t mind
steel splinters in your face, or arms then you can pass on the
shields, but safety glasscs are absolutely necessary.
I’m assuming you Don’t have a #2 or #3 carbide or HSS center drill
to start this hole, so this is the down and dirty approach to
getting your drill threw what ever it is your drilling?
When your ready… Turn on your drill, and generously apply the oil
to the spot mark of your hole and to the side of your drill tip.
Remember Don’t let the drill rub on the surface of your part… A
good steady controlled push threw, that cuts into the material below
the surface, then pull back out of the cut. "Don’t dwell the drill"
Then back the drill away (if you still have one) inspect your hole,
and your drill. Hopefully you have just pushed that drill threw the
surface, cut into the lower material, and have a good chip of
material their somewhere. If the drill edge has rounded over dull,
and you have not taken any chip of material…youcve got a battle
ahead still. If you did get a chip of material… good for you!
Although that surface still may have damaged your drill. Depending on
how scary that first cut sounded, you may consider changing that
drill and taking another poke at it, before trying to finishing he
hole.
Finish drilling the hole. Oil up again, and bring the tool up close
to the point of contact. With a steady, and firm motion feed the
drill into the material for 2 - 3 seconds. Back out just enough to
for the chip to clear, and more oil, then engage the drill back into
the cut. With a steady and firm motion peck drill your way threw the
part adding oil on every peck. Don’t dwell on the surface, push your
way threw the material. The drill must always be cutting, and making
a chip when its tip is in contact with the material. You should be
able to peck 1/8 diameter hole threw a 1/8 thick part with 3-6 pecks.
When drilling on a manual drill press… pecking helps by breaking
the chip, keeping temperatures down, and maintaining good lubricity
at the cutting point. Remember dab plenty of oil on the drill as you
go. If your drill seems cut with more difficulty for any reason, pull
out, and change the drill. If your having that much trouble drilling,
your most likely not drilling 300 series Stainless Steel.
If your drill did just melt, then I think you have something a th=
atcs been heat treated to 40 plus Rockwell. You will need to clear it
all out with more grinding… Then try a cobalt 135 TIN stub drill.
If that me lts… then you may be up past 50 Rockwell, try setting
it up on something more solid like a milling machine. Try using a
carbide end mill to clear out the melted cobalt and TIN from the
surface of you part, then re-spot the hole with a carbide center
drill, and use a TiAlN coated, coolant through, 135 degree solid
carbide split pointed drill at 4000 rpm with a 1500 psi high pressure
coolant system to Maximum bust… If that Don’t work. EDM out the
fused carabid from the surface of your part, and make a up a 1/8
diameter carbon electrode, and sink it in on a EDM sinker.
Good luck drilling your mystery stainless steel…
Derek