How to Extract a Broken Bolt with your Welder

extract broken boltWe all know about tools like an easy-out. But I want to explain an easier way to extract broken bolts especially if they are large bolts. Now this is not to be used in all situations for the simple fact that welding produces sparks. I wouldn’t expect you to fire up the welder under the hood of your Corvette because you broke a bolt off on the intake manifold. This is more of an industrial/farm application and for things you can protect well from sparks.

Let’s say you broke a bolt off flush to any sort of casting surface. Let’s say it was a 1/2″ bolt. Grab a 7/16″ or 3/8″ flat washer and put it directly over the remaining bolt. Now using the welder (preferably a wire feed) weld the flat washer to the bolt right through the center hole of the washer. Now grab a nut that will fit on the washer nicely and weld it to the flat washer. You just need it to hold so you don’t need to weld the crap out of it. Give it just a minute to cool down and try to extract the bolt. 80 – 90% of the time the bolt will come out with ease. The heating and cooling of the bolt will tend to make it come loose quite easily. If the weld breaks off of the bolt, try it again. Sometimes if a bolt is really rusted in you will need to put an even bigger washer on top of the smaller one and use a bigger nut so you can use a bigger wrench. Just make sure that every weld you put on is a good one or you will have to do it again. If it still won’t come out and the welds did not break, you might need to heat up the area around the bolt with a torch. This will make the casting threads bigger and then you can extract the bolt. This type of heating is another full topic by itself so I won’t get into it in this post.

Now let’s say the bolt broke off inside the casting and is inside 3/8 of an inch. If you have good control of your welder you can build up the weld on top of the bolt with out ruining the threads of the casting. Again the bigger the bolt the easier it will be to do this. Also, a wire feed is almost a must to do this maneuver. Once you get the weld high enough to weld a washer to it you are home free. They actually make a certain kind of welding rod for this very thing. I can’t for the life of me remember what it is called but, many years ago I used one of them. What happens is you strike an arc in the center of the bolt and the flux flows outward faster than the metal so it insulates the threads. If I remember the name I will update this post. Otherwise, just try Google.

This is just a tip I have picked up over the years of fixing things. It isn’t the kind of thing you will do day in and day out but, You might need to try it sometime.