Hi White Lightning:
You wrote:
"Break carbide off 7 in deep and it will be in a edm for weeks"
Yep...you'll get no argument from me on that.
So it's all about which decision gives the least pain if things go wrong.
The OP has indicated he could cut the spoiled end off (at least it sounds that way) if all goes to shit.
If that's the case there's not that much to lose by trying to drill it out.
Just don't break off the carbide drill...easy to say, right?
Seriously though; I've had to do this maybe a dozen times over the 45 years I've been a toolbreaker, and I've always gotten away with it.
If you look at that drill I butchered together, you can see the flutes are really shallow so the core is nice and stiff.
It's the same diameter as the hole it's going down, so it centers itself nicely and won't walk off the broken drill web and crunch things.
Once you get a feel for how hard you can push it, it goes pretty good...at least that's how I remember it.
I always had to sharpen my carbide drill a lot, and I did better with the hole horizontal so I could blow out the chips better.
A long skinny tube on the end of the air gun helped too.
Cheers
Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining
On a last note...if the OP really wants to find an EDM vendor, Reliable EDM in Texas is probably his best bet.
They specialize in big stuff, but I'll bet it's going to be an expensive hole: a ten foot long roll is a fair sized beast even to ship and rig.