I have an 01' Cobra and when working on the rear suspension had removed the emergency brake cable mounting bracket and small bolt that is attached to the bottom of the lower control arm. Well the bolt snapped off, and all my attempts using bolt extracting techniques failed, and so I decided to just drill out the remaining bolt and through the metal to use a heli-coil or similar to rethread.
During this process I broke 2 drill bits off in the hole and there is still some of the bolt in the hole as well. I bought a quality cobalt drill bit and have drilled for 20-30 minutes and the hole is like the hardest, solid metal and I'm making zero progress it seems. I've tried low torque/low speed, high speed, everything and I'm not making progress. It seems that between the metal from the control arm itself, broken drill bit pieces, old bolt, etc. the heat has molded them all inside that hole to the hardest metal combination ever which I can't drill through.
I'm using a handheld drill and I can't get the control arm off where the hole is to use a drill press. I do have a 1/2" hammer drill as well I haven't tried and not sure if it's more powerful than the handheld drill. I also believe a lubricant is needed when drilling metal to keep it cool. I was using penetrating oil and spraying in the hole while drilling.
Again at this point all the metal in the hole has seemed to weld together and I'm way past any bolt extracting methods. I need to drill about another 3/4" to 1" through to have a hole all the way through. The hole size is roughly 3/8".
What in the world do I need to do, or technique should I use to drill out this hole? All the YT videos I watch make it like using the cobalt bit should chew up the metal and drill through, but that's not working for me at all. Maybe I'm not using the right torque and speed setting, but I tried multiple settings and none provided success. Maybe I'm not using the proper type of drill lubricant either and need to use a different kind. Please let me know a better method for drilling out this hole so I can repair it.
Edit: Added stock photo of IRS control arm and hole location for reference