What is the issue?Bolts, like almost every fastening, have a tendency to seize up on boats due to the challenging sea going environment. They can often sheer off when load is applied to the head.
Why address this?A sheared off bolt can halt a project, cause frustration and cost money. If you fix things on boats you will have come across a stripped, rusted, broken or smooth stud at some time or another. So being prepared helps.
How to address this?If you are lucky enough that the sheared off bolt has left a section protruding it is a far easier task as there are tools that specifically cater for this event.
The normal resort for removing a sheared off bolt with its body protruding is with a vice grip. However, sometimes the jaws of the vice grip are not strong enough to get a firm hold and it can slide around.
One of the most reliable approaches to removing a stuck bolt is to get a nut of the same size and welding it over the sheered head. Heat the stud area up red hot and let it cool. The heating and cooling action fractionally expands the metals at different rates helping to break the metals apart. Don’t apply too much heat as it can cause the fastener to soften its temper and perhaps break off. Once it is cool place a breaker bar on the newly welded nut and wiggle it loose.
This method is best for 6mm (¼ inch) bolts or larger, and the shorter the better. Welding works in almost all instances. If, however, you do not have a welder, or it is in an area that you cannot heat to that level there are specially designed 'stud extractor' tools that can be relied upon. As long as the shaft is sticking out these tools will get it out, saving hours of frustration on broken, rounded, painted over and rusted tight bolts.
In all cases, before you attempt to liberate a seized exhaust stud with these tools you should use some penetrating oil - see releasing seized nuts and bolts - and if possible applying some heat will always help.
Photo: Courtesy of ARES
The best of the two types of stud extractors is the more modern one that looks like a drill chuck, as shown above. It requires about 6mm (¼ inch) of the broken-off shaft to grip upon and then it extracts it easily. The universal design of this tool allows you to clamp down on any damaged, rusted or broken stud. Its hex drive can be a driven by a wrench, breaker bar and socket, or impact tool.
In use make certain you are dead centre and remain dead centre while turning. As you apply turning motion the tool has a tightening jaw that binds in on to the bolt. Take it steady as it has such gripping strength it will shear off a stud if you let it.
Unfortunately, the threads on a tightly seized stud will be annihilated by this extraction method. One of the problems with this particular tool is that its self-tightening tends to lock into the stud jaws of the extractor after it has been removed. This may require some finessing to remove it from the jaws afterwards.
Photo: Courtesy of KD Tools
The other option is the traditional knurled roller bolt extractor. This tool uses cam action to grasp the stud firmly and depends on the little wheel wedging itself around the stud. On hardened studs this tends to be difficult, as the cam slips around these studs and is unable to bite in. On softer materials they have a tendency to strip the bolt and shave metal off without budging the screw, leaving you worse off than when you started.
For these reasons, the chuck like version is broadly seen as the better option. The only advantages that the traditional bolt extractor has is that the extracted bolt does not get jammed into it and it will also work on a left-hand threaded stud.
If you do no have these tools you are reduced to locking a pair of nuts together and trying to turn out the stud with these and a couple wrenches.
With thanks to:Bernard Harpur, Co. Wexford, Ireland
Removal by welding
Broken Stud Removal Techniques
Remove a threaded stud using two nuts and a couple wrenches
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