Hardest metal I've run into

At least recently! S-10 Blazer, exhaust system, between cat converter pipe and muffler pipe. They have flanges that bolt together. One of the bolts broke on it"s own - No brainer - replace the bolt. Turns out that"s not that easy. The bolt(s) (broke the second one getting it off.) are harder than heck. Turns out there aren"t even bolts, but studs, kind of like wheel studs. Heads are frozen in the flange. So pound "em out. No luck, even with air impact hammer. So drill "em out, very difficult. Did force a 1/8 inch drill - carbide, with exteme difficulty. About destroyed the drill, had to sharpen it a couple times to drill the half inch or so. Tomorrow, I"ve got to figure out how to enlarge the holes to at least 3/8 inch. And of course, the holes aren"t centered - drill walked something fierce. I don"t have a torch, that"d be too easy. Can"t remove muffler assembly without cutting it up, as it is a one piece unit over the axle. What"s worse I"m working under the car, sitting on the ground. Going to try to get a carbide burr to use on my die grinder. I ground part of the stubs off with a angle grinder, but was slow going. Any other suggestions? (I can"t imagine why those bolts are so hard.)

A suggestion on a hard bolt is to drill SLOW with a good sharp bit and some type of penetrant. I like to use a thin tapping fluid. When you drill fast it workhardens the metal and is a bear to get through, especially with a hand drill.
As for grinding the hole out, I like to use a die grinder too, but they actually go too fast on hard stuff. If a carbide burr doesn't do it, maybe a diamond coated burr might work. I've used some of those cheapies and got the job done before they wore out. Good luck.
Irv

Heat the flange and the studs will hammer right out. Done it lots of times.

I've knocked them out with an air hammer before, try backing the flange up with hammer to take out the vibration.

get some titanium drill bits, those studs are most likely stainless of some kind. most exhaust fasteners these days are . the easiest fix is to heat the flange and knock them out and just use bolts, but if you have to drill them those bits will usually cut stainless, just turn them slow.

I was thinking die grinder too, its going to be a slow go. If its the studs I am thinking of they are pressed in from the opposite side and as you found out, they are hardened.

My favorite tool for dismantling steel is the cutting touch, aka gas axe. Next come the sledge hammer, chisel, plasma cutter, pry bar...

arrrgh, I know what you mean, laying on your back wrestling with something is a big pain.

Rick

Spend $30 on a cheap Coleman propane torch. Takes a little longer but it will heat things up.

As I know they're stainless. I replaced the same bolts in a K1500, and tried to blow them out with a torch, but couldn't get anywhere. I ended up heating them, and hitting them out.

Hey Ray.

You are in a tough situation. I would suggest renting an ox/acet cutting torch if you know how to use one.

I have a Purox w300 and bought its twin, a Prestolte on ebay for about twenty bucks.

Good luck,

Brad

Well, I got one out. Heating with propane torch didn't get anywhere, not did hammers, including a pretty good air-impact hammer. Was able to drill through it with a 1/8 inch carbide drill. Today I picked up a couple carbide burrs for my die grinder. Carefully applied, they are grinding out. My guess is that origionals were force fit, much like rivets in steel construction, made of stainless, and what's worse, they hardened in response to the many heat/cool cycles and welded themselves in place.
Was able to grind off the heads fairly fast with a 4 1/2 inch angle grinder...

Got the second one as well. Mostly grinding it down to nothing with a carbide burs on my dir grinder. Very hard metal, perhaps from all the heat/cool cycles, and being adjacaent to cat converter, probably pretty hot. They were just like wheel studs with splined shoulders, which were probably heat welded in the flange as well.
All in all, a real mean project, that should have been pretty simple. May have been some version of stainless, but can"t prove that by me.

Reassembly took about 5 minutes, once I got all the grinding done.