One of the biggest frustrations when disassembling a vehicle for restoration, or even repair, is the dreaded seized or stripped bolt. Stuck hardware occurs when a bolt or nut gets corrosion between the threads and they won't budge. Many times this leads to breaking the bolt off and having to drill and retap the hold or trying to remove it with a bolt extractor. I won't even mention what happens when the drill, tap, or extractor breaks off in the same hole!!
Below are my top 10 ways to deal with getting these suckers extracted without wrecking the precious part they are in!
1. Blunt Impact/Force- This is usually my first step when attempting to loosen stubborn bolts. I ALWAYS use this method before I begin removing exhaust studs from a cylinder head. There are a few methods for this. One is to hit on the head of the bolt in the center with a chisel or punch. Another is use an impact wrench/gun and hit it a few brief times in reverse and forward. Either of these methods work on the theory of freeing the corrosion bond between the threads by vibration or impact. It works sometimes on lightly seized bolts, but isn't a 100% winner every time. But keep in mind it can be combined with many of the other methods to help make the job easier.
2. Heat- If you paid attention in chemistry class you would have learned that when you heat and cool metal it expands and contracts. The way that I have used in the past is to heat the head/body of the bolt until it is almost red hot. By doing this the bolt expands due to the heat, and when it cools it will contract thus breaking the corrosion in between the threads. A similar method is to heat the area around the bolt to make the hole it is threaded into actually expand and open up a little bit so that the bolt fits a bit looser and can be threaded out. Use of an impact wrench/gun helps when initially breaking it loose since the force from the hammering of the impact wrench breaks the corrosion apart as well. Use penetrants like Kroil or CRC Freeze-Off to aid in the removal process.
3. Relief Cuts- This method is my "sure-fire" method for removing most stripped bolts/nuts. It isn't as clean/civilized as the others, but it is a heck of a lot faster! With this method you will be putting 2-3 cuts in the bolt head or nut. You want to cut just enough that you are almost all the way through the head of the bolt or the nut. You then can hit the cuts with a chisel and a hammer a few times, thus splitting the nut or bolt and relieving the tension on them. With nuts you can normally just split it off of the bolt, clean up the threads, and install a new nut. With bolts you can use some locking jaw pliers to grab the bolt head and turn the bolt out, usually the relief cuts will let the pliers squeeze the head of the bolt enough that you can turn it out easily.
4.Rock the bolt- This is another one to try early-on in the process, and in conjunction with other methods. You want to slowly work the bolt/nut back and forth. I like to take a ratchet and loosen the nut/bolt a little bit until it gets a bit of tension behind it again, then go back the other way and turn it almost to where you started, before loosening a little bit further than last time. As you expose some of the hidden threads, you want to spray some penetrant on the those threads so that the penetrant works its way back into the hidden threads. It can be a slow process, but I've gotten some pretty stuck bolts out this way with a little bit of patience.
5.Drill'er out!- This is the same concept as the relief cuts with a couple small twists or surprises that can occur along the way. I like to use this one as more of one of my last ditch efforts, or if the bolt has broken off flush with the surface. What you want to do is take a small drill bit and drill all the way through the bolt. This uses a bit of the chemistry a few of the other methods use. It heats the bolt by drilling it, and it also makes a hollow portion in the bolt so it can contract more as you attempt to remove it. I've had times where just drilling the bolt will allow the bolt to turn out quite easily. Other times you may have to keep stepping up your size of the drill bit with a drill index until you are just a bit smaller than the diameter of the bolt. At this point you may be able to carefully chisel or break the bolt apart in the hole. You can then extract the pieces and clean the threads back up with a tap set or a universal tap tool.
6. Weld'er Up!- This is one that can be used if the nut or bolt head is so severely stripped you can't turn it with locking jaw pliers, or if the head is broken off the bolt. You can simply take a washer and a bolt of a slightly larger size and tack weld it to the bolt body. Once you have it tack welded, I like to fill the nut with weld and run a bead around the base of where it meets the bolt body. This allows you to put a socket on the bolt again, as well as puts heat into the bolt that will allow it to expand and contract, breaking some of the corrosion. I prefer to use a Mig Welder to do this job as it allows for a little more control than with a stick welder.
7. Air Hammer/Chisel- This combines a few of the methods mentioned. But can be used when the bolt head is stripped. You basically chisel/hammer it so that the bolt loosens. Have had it work with moderate success, but needs to be on a bolt/nut that is an open area.
8. Bolt or screw extractor- There are many styles/gimmicks. Some work, but many do not. They use hardened bits that grab into the inside of the bolt or nut to remove it. Many you have to drill a small hole in the bolt, then thread these in. Just whatever you do, DO NOT break the extractor off inside the hole, or you are in for a long, horrible process. Normal drill bits will not touch these, so you will need specialty drill bits to drill through them.
9. Pipe Wrench- This is a pretty basic way to tackle a stripped bolt, and most everyone has a pipe wrench kicking around their shop. Tighten the pipe wrench down on the bolt/nut and as you crank on the bolt with the pipe wrench, it actually grabs harder onto the bolt head. Just watch you knuckles if it slips off!
10. Reinstall bolts that surround the stuck bolt/nut- Sometimes a number of bolts in a area will hold a part on. Occasionally these are meant to be removed in a specific order. Make sure you check your repair manual for any installation/removal order. If none, I like to work from the center and work your way to the outside. Reinstalling some of the bolts around the stuck bolt may take some of the force off of the stuck bolt and allow you to remove it.