Broken exhaust manifold bolt CM870

[DVT873]

Used one of these for the first time about 8 or 9 months ago. I think it was the smallest one. https://www.theoriginalrescuebit.com I use this small die grinder to run it http://corporate.cornwelltools.com/webca...nder.html# Over the last 45 or so years I have seen and tried just about everything for removing broken bolts and studs except EDM. Until I tried one of these, carbide burrs in the die grinder was as good as it got. Had an exhaust manifold bolt broken off in a tight place. Compounded the problem by breaking a bit off in it. My bad. No good access for a mig. Was down to pulling the head or lifting the engine enough to get it above the frame rail. This was a little "toy" V8 diesel in a medium duty truck. The packaging sucks. So I saw this and thought OK I'll take a shot. Didn't really have much hope it would live up to it's claims. I was wrong. These are very very hard. Not only does the tip cut so do the flutes. I have a set of hardness testing files. I couldn't make a mark on these. Had a question and the owner/inventer actually answered the phone. Seems these have been around for a while but I had never come across them. Have used it maybe 4 times total now. It will gut that bolt in less than 2 minutes. Whats left of the bolt threads will fall out or can be picked out. The faster you can run it the better and it runs dry. Last use was on a DT466 that came in with 3 exhaust manifold bolts pre broken off flush with head. Got the manifold off and went after the broken bolts. About a minute per bolt. Next time maybe I will break a tap off to make it a challenge!!! Just kidding