Extracting Broken Bolts and Studs


You suddenly find yourself with a wrench in one hand with part of the bolt or stud you were trying to extract, and the rest of it still in the manifold/head/block/suspension bit? Contratulations - you're about to have an adventure.

I've been there. After you've worked on old cars for long enough, it's inevitable. The most recent occasion was on my TR4A, where someone had used a piece of threaded carbon steel rod to replace an exhaust manifold stud. You can get the remains of the stud out without removing the head.

You will need:

  1. patience
  2. dremel tool with small grinder bit (carbide is best)
  3. patience
  4. heat wrench (propane, MAPP or oxy-acetelene torch)
  5. patience
  6. reversible drill
  7. patience
  8. collection of ez-outs and left handed drill bits to match, plus drill stops
  9. patience
  10. a drilling template
  11. patience
  12. sharp punch and hammer
  13. patience
  14. penetrating oil (I think Kroil is best, many like PB Blaster)
  15. patience
  16. a properly sized tap
  17. patience
  18. a little luck

A scribe and a small round file may help. You might want some extra patience, too. If you get frustrated in the middle, take a break and come back to it the next day.

Extra credit trick for those with the appropriate tools and skills: if there's any of the piece sticking above the surface, try welding a nut, one size smaller than the threaded portion, to the broken stub. Weld the inside. The heat from welding may break the corrosion bond, and the nut gives you something to grab and turn. Be careful.

The starting trick is to get a hole drilled into the center of the stud. This is the point of the drill template - I made mine by copying the holes in a manifold gasket. Make the hole you're going to drill just larger than your starting drill bit size - I usually start at 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; aluminum plate is better. You want adequate thickness to make sure that the drill bit is at an exact right angle to the manifold face. If the item is broken off significantly above or below the surface, you may be able to buy/make a bushing that surrounds the stub (or fits the hole) and use the ID of the bushing as the starting drill size.

Drill. Use the drill stops! You don't want to drill deeper than the broken piece. Make a good center 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 center, because gaskets aren't made perfectly; do the best you can. Go up in size until you are in danger of cutting into the threads in the head; inspect often with a mirror and flashlight (tip: point the flashlight into the mirror).

If you're very lucky, the heat and vibration of drilling will break the bond. This is why you want left-handed bits - if this works, you'll pull the piece out, rather than driving it further in.

Use the EZY out. 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 twisting the EZout in farther. But the twist ones are more amenable to weird hole sizes. Chances are that you won't get anywhere with the EZ out, but try it anyway. Don't break it off, whatver you do.

Heat the area with the heat wrench, spray on some Kroil, PB Blaster or WD-40, 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 terribly 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 torch the better - try to get the part red hot.)

There is a new generation of tools that combine left handed drill bit and ezout and even claim to center themselves. They're very expensive, so I haven't tried them yet. They just might make this job a little easier.

I will usually 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 sometimes works. Don't be surprised if it doesn't. And, again, try not to break the ezout.

Consult a tap drill chart. Determine the next 1/64" smaller than the tap drill for the broken piece. Work up to this size in 1/16" steps then STOP. Grind a chisel on a 1/16" dia. music wire 4-6" long. Work this around the stud remnants and gradually collapse them inward with gentle taps of a small (8 oz. max.) ball peen hammer. Use a magnet-on-a-stick tool and move it around to dislodge the pieces. When the first sliver comes out, repeat the tap - tap step. Usually they are reluctant but do come out.

If they don't come out, or you have a less then complete selection of drill bits, you can try this - very carefully. Using mirror, flashlight and dremel tool, grind outward from the hole you've drilled. Eventually, you will start to see the ridges of the thread cut into the head poke through the stud material. You can get away with removing a smallamount 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 fractional piece of the stud in the threads.

You can also take the file to the hole and enlarge it, and then try the above methods.

Finally, you can use the file (or a small grinding point on a Dremel) to remove the first couple of threads of the stud (using the scribe to pick the pieces out of the troughs of the manifold thread).

When you have achieved this state, you can start using the tap to remove the remaining metal. Finish the hole with the proper size tap drill liberally coated with grease. This will clean out the remaining chips. Run the tap in and then out (chase the thread) then use the greased tap drill again. Voila! (The grease on drill and tap works great when you must put a Helicoil in a spark plug hole.) Best is a tap with a tapered start, so you can get some purchase in the hole you've drilled; once you've removed a bunch of the metal, you can switch to a plug-style or bottoming tap to clean out the deeper grooves. Chances are that the trapped material will break off in complete rings, which you want to remove - pull 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 clear the shards. 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 manifold, but that shouldn't matter much.

Center punches, etc. are always off center; Murphy's Law #726. Either tilt the punch toward the center and hit it some more (driving the mark toward center) or start the 1/8" drill on the mark but just barely. Tilt the drill so as to drill the hole toward the center. When you can straighten the drill and the hole is centered, the hole should be no more than 3/16" deep so go slowly! This first bit of hole is the most important to the whole job; a few minutes here repay themselves quickly. Between the punch and the drill, this works 10/10 when you have room. I often end with a tap drill and loose no more than about 0.005" thread. Remember: if you are off center 0.015" (two hairs) even a Helicoil may be too far off center to save you.

I spent three or four evenings in the process of removing a broken stud from Sarah's head. It was not pleasant, but it beat the hassle and expense of removing the head.

I have spent weeks getting a stuck tapered plug out of a cylinder head. Like it says in the list above, patience is important.

Oops again...

So you broke off the EZ out? Now you're in bad shape. Take the part in question to a machine that has a plasma cutter or an EDM (Electrical Discharge Machining) machine and get them to remove the remains. They'll cut that sucker out in nothing flat, very precisely. It probably won't even cost much, but you *will* have to remove the part in question.

If you're good with a welder and brave, you can try welding a piece of stock to the broken bit to give yourself some purchase to turn it all.

How to avoid this

When you get it all done: make sure you use 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 lock washers, so they don't corrode in place (TRF sells the brass nuts, as do most auto parts stores; go to a marine supply for the stainless kit). ARP is starting to manufacture stainless studs for British applications, but I don't think they have any for Triumph yet.

Thanks to "ReameyP" at AOL for some additional tips and techniques!

There's a ... strikingly similar page to this one, with pictures, here. You might enjoy taking a look at it.

There's also a rather different technique, which I picked up from a Moto Guzzi list. I've never tried it, but it sounds intriguing:
Get two visegrips and a BIG battery (don't waste yer time with some battery charger) and some jumper cables. You clamp one of the vise grips to the stuck bolt/stud/screw very tightly on a shiny part so you got a good connection. The other vise grip you clamp very tightly on a close by ground (don't clamp on a rear brake bleeder and use the stock ground in the front). You connect both the jumpers to the battery and the other end to the stuck bolt vise grip. Then the fun part, you QUICKLY clamp the other remaining battery jumper to the ground and there will be a BIG spark! Wait 2-3 seconds and take it off and try to wiggle the part, if nothing happens try again. It will eventually loosen the part, because corrosion has more resistance than good clean metal. and you will blast the rust/ oxide out with the maybe 4-600 amps you are putting through it. Sometimes there will be a small puff of smoke. Polarity doesn't seem to make any difference. I have been doing this for 50 years since I read about it in Popular Mechanics.
If you try it, let me know how it works!

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This page brought to you by Chris Kantarjiev of The Dimebank Garage.

Last updated 13 May 2010 by cak

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