A little background. My first career I was a machinist in a couple different FAA repair stations that repaired piston-engined crankcases. Lycoming, Continental, and the occasional Franklin. These were opposed/flat engines with aluminum castings that ranged from 4 to 8 cylinders. Most of them had cracks or damage that we welded, occasionally we’d get a clean one that only required machining. We removed a number of studs prior to inspection and any welding needed. After welding the cases would come to the machine shop, where I would often need to remove a couple more studs.
I’ve taken out hundreds, maybe thousands of studs throughout that career. We used this set from Snap-On. The part number is CG-500. It works a lot better than jamming two nuts together, (which you don’t have enough threads showing to do anyway). Rather that put a shear load against the threads like you would with two nuts, this tool puts a compression load on the stud itself. It’s basically a four-jawed chuck, if you will, that clamps down on the stud body from the North, South, East, and West. If you tighten it well, it will not spin on the threads when attempting to remove the fastener. It may snap the bolt or stud in two, but it won’t spin on the threads if tightened adequately. It also won’t damage the threads. You can tighten this like a gorilla, remove the fastener, un-tighten it, and the fastener is not damaged. For real. It also has the added bonus of allowing you to install the tool, then smack the end of it a couple times with a hammer to try and break loose any corrosion.
It’s an expensive set, I bought this set for home use 30 years ago and I think it was $300? You could just buy the mandrel and the collet that you need for your size bolt without having to buy the whole set. Hard to tell from the pic but it looks 5/16-18, maybe 3/8-16? I see you only have about three threads showing, I’ve removed fasteners like that before with this tool. It really does work.
Sometimes the fastener is corroded/seized and simply will not back out. PB Blaster/Liquid Wrench, wax, heat, impact wrench, etc. don’t help. It’s stuck. I’ve snapped off 7/16 Continental and 1/2 Lycoming cylinder hold-down studs before trying to get them out. And yes, I could easily remove the broken stud from the tool once loosened. The threads were fine. We had to move on to plan B.
Now on to some other methods.
Welding a nut on the fastener. This works most of the time, damn near all the time. I’ve seen it not work a number of times, though. What you’re left with is a lump of hardened steel. Depending on the alloy the fastener is made from, as well as the alloy the welding rod is made of, it’s very difficult to subsequently try to machine the metal. High-speed steel end mills, center drills, drill bits etc. would simply dull and not cut. The metal had hardened from the welding. I wound up buying solid carbide cutting tools to machine through the welded steel. So welding has that inherent risk. We didn’t worry about it that much in our shop, because we could simply grind out the affected base metal until the stud came out, then weld the crankcase solid in that area and drill and tap new threads. You don’t have that luxury. If you're going to have it welded, I'd stay away from a stick welder and use a TIG.
EZ-Outs or extractors. As has been noted earlier in this post, they will expand the fastener in the threads. Do they work, absolutely. Until they don’t, and now you’re left with a broken EZ-Out in the fastener. You’re not going to drill through a broken EZ-Out in your garage, they are hardened steel as well. So once again, there’s an inherent risk involved once you break out the screw extractors.
Drilling it out. My preferred method if the stud puller won’t work. If you elect to drill it out, I would HIGHLY recommend two things. First, don’t skimp on drill bits/cutting tools. Harbor Freight is not your friend in this instance. Go to an industrial supply website and buy good quality drills. We used JL Industrial Supply, there are other good ones out there as well. Stick with a name brand like Irwin or Dormer. I’ve been out of the industry for 25-30 years, so there may be other good brands out there now. Second, and
I can’t emphasize this enough. Buy drills that cut in the opposite direction of the threads on the fastener. So for a standard right-hand thread, buy a left hand drill. I say this for two reasons.
One - As has been previously noted in this thread, often the drill will remove enough metal so that at some point in the process the threads will “let go” and the partially drilled fastener will start turning and back right out. I’ve had that happen a number of times with left-hand drills.
Two - Blind holes. I’m talking about a hole that has a bottom to it, as opposed to a through hole, which is open on both ends. If you’re using a right-hand drill, and the fastener begins to rotate (like in the preceding paragraph), the stud will hit the bottom of the blind hole, stop rotating, and you will snap your drill in two before you can react to what is happening. I’ve done it. Once. (After that is when I ordered the left-hand drills, by the way.) A left-hand drill won’t bottom the stud out in a blind hole the way a right-hand drill will.
I’m not sure about the hole you’re dealing with, whether it’s blind or not. Someone on this forum will know.
Hope this helps.
