On 14 Jan 2004 21:58:20 -0800, (Ben) wrote:

I recently discovered carbide drill bits. Wow, heavy, big, gold(TiN),
and expensive.(Cheap on the bay). So, I drilled an 1/8th i hole
through a 3/8 tap. What a thrill, but it took 2000 rpm on a drill
press to do it. I think it spot annealed, then drilled a bit, then
spot annealed etc.
So I ran out and got a 5/16 carbide tipped die drill from ptd and a
5/15 hiroc drill. Also a 1/8" tile bit too.
Put it in my Rigid 18v and tried to drill through a 6" mill *******
file. No chance. Used the carbide tipped die drill on a piece of 1/4"
plate. Yeah, it'll drill, it just doesn't want to. Cobalt works fine
on this.
If it cant even drill through a file what good is it?
Why cant you use soild carbide jobber bits with steel?
One place claims their M-7 bits will "drill through" my new CTD cobalt
drills.
BS? How can m7 drill through m42? Is there a carbide drill that will
"drill through anything this side of roswell", quicky, smoothly,
acting just like a jobber drill in steel?
Anybody heard of http://www.icscuttingtools.com/Products_Drills.htm?
by the way, they look good, but will their drills be as good as
cleveland twist?
Because the file is hard it will take lots of pressure to drill
through unless you are using abrasive, So no carbide drill is going to
go through a file like it was mild steel. Your observation that the
metal seemed to anneal is sort of on target. Used properly, one
advantage of carbide is the relative hardness compared to the material
being cut. With the proper pressure the metal being cut deforms and
heats up because of this deformation. This in turn softens the
material so the relative hardness of the carbide becomes even greater.
I.E. the red hardness of carbide is much higher than the red hardness
of the file you are drilling. Since carbide is so brittle it cannot be
ground the same as, say, a cobalt HSS drill. This means that it will
take more pressure to drill a soft material because the cutting edge
is ground to have enough strength to support it and this grind does
not penetrate as well. Another thing to consider is that it is hard to
get a drill press to keep the constant pressure needed to make carbide
drills perform best. Using a hand drill would be really hard to do
with carbide.
ERS