HOME RESTORATION. Removing Broken Bolts and Studs.
Sooner or later you will find yourself with a spanner in one hand with part of the bolt or stud you were trying to undo, and the rest of it still in the manifold, head, block or suspension bit? After you've worked on Mini's or any other car for that matter , it's inevitable. You can get the remains of the stud/bolt out.
You will need some of the following:
1. Collection of EZouts and left handed drill bits to match, plus drill stops
2. Reversible drill
3. Heat (oxy-acetylene)
4. Pencil grinder or dremel tool with small grinder bit or Burr (carbide is best)
5. A drilling template or guide
6. Sharp punch and hammer
7. Penetrating oil (WD 40 etc.)
8. An appropriately sized tap
9. Vicegrips
10. Luck
A scribe and a small round file may help. You might need some extra patience, too. If you get frustrated, take a break and come back to it. The first thing to try, if there is some of the stud or bolt sticking out, is the trusty pair of vicegrips. Grab hold and just unwind, but very rarely are we this lucky so alternative tactics are needed. The trick is to get a hole drilled into the centre of the stud. Make the hole you're going to drill just larger than your starting drill bit size - I usually start at 3mm (1/8) and work up, but it will depend on what left handed bits you can find. You can make the template out of plywood or aluminum plate to help keep you on centre. You want adequate thickness to make sure that the drill bit is at an exact right angle to the part you are working on.
Drill. Use the drill stops! or mark the drill bit with masking tape. You don't want to drill deeper than the broken piece. Make a good centre punch to try to keep the bit from wandering (especially if you don't have a drill template). Chances are that you won't get the hole dead centre, do the best you can. Go up in size until you are in danger of cutting into the threads, inspect often with a torch if needed.
Left handed drills. As the name suggest turn in a left handed direction, in some cases they will just wind out the broken part out part of the way through the drilling operation. If you can get some in the sizes you need they are worth the effort.
EZouts. There are two sorts - straight fluted and twist fluted. I prefer the straight ones, because all the force is used to turn the broken stud, rather than wedging the EZout in farther. But the twist ones are more suited to the odd shaped hole you may end up with. Chances are that you won't get anywhere with the EZout, but try it anyway. Don't break it off, whatever you do. Heat the broken part with the oxy, spray on some WD-40 or similar, and wait. Repeat several times. This might help, it might not. Try the EZout again. Repeat until you're frustrated and ready to go on to the next step, or, if you're lucky, the blasted thing comes out. (It may take several days of this cycle to succeed. If you're not in a hurry, this is the safest way. The hotter the oxy the better - try to get the part red hot, remove the EZout when doing this or you will anneal the EZout and it will break very easily) I have been told to try a small impact wrench at this point: find an 8-point socket that fits over the square end of the ezout and blast away. This may work. Don't be surprised if it doesn't. And, again, try not to break the EZout.
There is a new generation of tools that combine left handed drill bit and EZout and even claim to centre themselves. They're expensive, as yet I haven't tried them. They just might make this job a little easier.
If you're now to the point where the next larger drill bit will start removing threads, you have to proceed carefully. Using torch and pencil grinder, grind outward from the hole you've drilled. Eventually, you will start to see the ridges of the thread cut into the part poke through the stud material. You can get away with removing a small amount of the crest of the thread - this will make the stud fit a bit poorer, but probably won't matter much. At this point, you can try using the hammer and punch to rotate the remnants of the stud in the threads. You can also take the file to the hole and enlarge it, and then try the two previous methods.
Finally, you can use the file (or a small grinding point on a pencil grinder) to remove the first couple of threads of the stud (using the scribe to pick the pieces out of the troughs of the thread). When you have achieved this state, you can start using the tap to remove the remaining metal. Best is a tap with a tapered start, so you can get some purchase in the hole you've drilled; once you've removed some of the metal, you can change to a plug-style or bottoming tap to clean out the deeper threads. Chances are that the trapped material will break off in complete rings, which you want to remove, unscrew the tap and use a sharp object to try to clear these out before tapping more. You want to reverse the tap often in order to break the chips. Use the tap to essentially tap a new hole - you want to go about 1/8 turn at a time, cleaning the tap every time. You'll probably lose the first couple of threads in the part, but that shouldn't matter much. So you broke off the EZ out? Now you have a problem! Take the part in question to a engineering workshop that has a EDM (Electrical Discharge Machine) or a plasma cutter and get them to remove the remains. They'll vaporize it very precisely. It probably won't even cost much, but you will have to remove the part in question from your car.
If you're good with a welder and brave, you can try welding a piece of bar to the broken bit to give yourself some purchase to turn it.
How to avoid this:
When you get it all done: make sure you use an anti-seize on the new studs before you install them, so you (or the person you sell the car to!) won't have to go through this the next time. On an exhaust parts, use brass or stainless steel nuts and washers, so they don't corrode in place. Studs do not need to be tightened into their holes.
May 2001