Will a plasma cutter cut a stainless steel stud out?
 

I have a broken stainless steel stud in one of those clamp type exhaust crossover pipes. The stud looks to be pressed into a flange that clamps the x-over pipe to the manifold. A std torch will not touch the SS stud. I have tried pressing the stud out with a c-clamp and of course driving it out with a punch. I have also heated the flange red hot and still no luck. The stud is 10MM in dia. If I can get the studs out I will replace them with std bolts. If that stud does not come out I am looking at a new convoluted x-over pipe that probably runs $500 from Ford since a tiny plastic bushing 3/8" of an inch across costs $5.15.:(

The short answer is yes, assuming you have sufficient power.
The best way would be to first minimize the amount of stainless you need to penetrate, and then drill a hole thru the remainder of the stud as a start point for the plasma.
You can also schive the stud away with the plasma just as you'd schive steel with an O/A torch.

A plasma cutter will cut anything that conducts electricity. It will cut the steel fange (or an iron manifold) equally well. Cutting out a broken stud is equivalent to doing a pierce cut. The best you can hope for is a cut hole diameter one-and-a-half times the flange thickness. And expect some scorched eyebrows, because when doing a pierce cut, most of the sparks will fly back at you. A full face shield and some leathers are highly recommended.

Don't forget to disconnect you battery cables if you don't want to fry the vehicle electronics as well. The high frequency arc start used in a lot of plasma cutters can wreak havoc. Even the arc voltage of a non-high-freq plasma machine can destroy electronics. Disconnecting the battery cables is cheap insurance (but it's surprisingly easy to forget to do it).

Drilling a starter hole through the stud may help keep the cut hole cleaner, but if you drill a pilot hole, you might as well drill the whole thing out, IMO. I'd use a 1/8" cobalt bit as a pilot and a 13/32 cobalt bit to finish the job. Use proper cutting fluid on the bits (not just oil) & the drilling shouldn't be too difficult.

Good luck.

Cheers,
Eric

Thanks for the answers! That stainless is tough stuff but not as bad a 316 etc. It is a tough spot to get to with a drill motor but that looks to be my best option. I had to cut both studs just to rotate the flange to where I can work on it at all. It was raining here all day so I did not get a chance to mess with it.

FUBAR!

I pulled the entire assy out of the vehicle which was a good thing. The "Professional" mechanic that installed the motor a few months ago for the PO (it never did run right) not only messed up the threads on the stud I was working on but the threads on the other side's manifolds have no threads. Heli-Coil time. At least that is cast iron. I have tried drilling the studs. Unfortunately whatever grade of stainless Ford uses work hardens. I drilled a 3/16" hole thru one stud but I am stuck on the second stud half way thru. I doubt that I will be able to push a 3/8" drill bit thru either. I can't get a good setup in the drill press to use so it is all hand drilling. With all of my 230 pounds I can't get enuf force on that 3/16" bit to cut. I have tried grinding the head of the stud off but that work hardens also. I am down to trying to melt them out of the flange with a OA torch.:-X09

Unfortunately this points up the biggest weakness in todays entire electronic engine management system: The O2 sensor is down in the crossover pipe for one bank on this engine. Downstream of a potential giant O2 leak. Just a giant F- design, but having them in the manifold is not much better because leaks can occur at the head-manifold surface also.:-X09

And some people wonder why I prefer the old iron from b4 computers...

I hope you are using cobalt (or better) bits & proper cutting fluid. It will make the drilling a lot easier.

If a cobalt bit doesn't do the job, you could step up to a carbide bit. Solid carbide bits are available from tool supply shops, but they are pricey.

Another option is to use a carbide-tipped masonry bit, but you have to prepare it properly first. Masonry bits have the cutting edge chamfered slightly. You will need to regrind it slightly to produce a sharp cutting edge. It won't take more than a minute at a grinder. The carbide will be harder than any stainless steel or cast iron you will try to drill through. Just don't expect it to cut through terribly fast.

My guess is that the bit(s) will be toast by the time you are done. But 10 bucks worth of drill bits is a lot less pricey than new exhaust parts.

Again, good luck.

Cheers,
Eric

I heated the stud where I was stuck and that took out the work hardening. I drilled the rest of the way thru with the 3/16" after that. I then used the torch to melt out as much of the stud as I could. I removed the remains with a punch. I used std HSS drill bits and no cutting fluid. Adding cutting fluid did not help. I slightly dulled two bits during the process. They would still drill thru wood. It won't take much to sharpen them back up.

I got the whole unit back on properly but I think I have a clogged catalytic converter:(

I like the way SS looks and have to work with it quite a bit, but it's really easy to strip. I'm always carefull not to over torque, (still happens, though.)

The stainless they use for exhaust systems is not shiny.

you have to polish to make it shiny.

They use a different grade of stainless for OEM exhaust systems that does not have a bright finish of any kind. It turns a dull brown with a slightly rusted look. It is not the same alloy that is used for aftermarket SS products etc.

Vinegar is supposed to be good for drilling stainless. Also you have to keep the drill cutting or the stainless will work harden.

I have never tried vinegar! :D

The 2nd stud I drilled work hardened but I was able to fix that with a little OA torch application.