Seized bolts can occur on any mechanical device. Typically the bolts rust due to excessive moisture and lack of any lubrication maintenance. Bolt arrangements make for a variety of extraction methods and there is no one correct way to remove a seized bolt. There are a series of steps that can be taken to remove and replace the rusted fastener.
Oil and Brute Force
The first step to removing any seized bolt is to drench the bolt and surrounding area with a penetrating oil. There are many types of spray oils on the market. Any penetrating oil will work if allowed to soak into the thread area of the bolt. Generally the oil must be allowed to work for at least six hours before attempting an extraction. Fit the head of the bolt with the proper-sized socket wrench. Attempt to work the bolt first in a counter clockwise direction then back a little in a clockwise direction. Exercise caution as too much force can break the bolt off inside the thread area. Employ the use of a hand-held impact wrench if there is enough room. In some cases, a few sharp strikes to the end of the impact wrench will free the threads and the bolt can be removed with the socket wrench. In some cases though, the bolt is so rusted that no amount of oil will work to free up the seized fastener.
Bolt and Nuts
Many times the bolt and nut are seized together, in which there is no removing the nut from the bolt. If room allows, a nut splitter can be fitted over the rusted nut. Use a crescent wrench to tighten the splitting device around the nut. This action ruins the nut and the bolt. In many cases, the bolt is easily replaced. When replacing the fastener, use some anti-seize compound on the new fasteners. The compound will work into the threads in case the fastener needs to be replaced in the future. Bolts that are inserted into a larger metal piece, with no nut holding them secure, requires a more drastic action.
Torches and Heat
Bolts that are secured into large metal pieces such as engine blocks are going to require the use of heat for the extraction. Use a small propane torch to heat the area around the bolt. Have the correct socket wrench in hand as the heat will quickly dissipate. The goal is to heat the metal around the bolt and cause it to expand slightly. Place the socket over the bolt head and turn quickly in a counter-clockwise direction. If the heat moves into the bolt, the bolt will also expand and removal is made more difficult. Allow the area to cool and try the torch again. The addition of the penetrating oil will aid in working out rust from between the threads during the heating process.
Use a wire feed welder on stud bolts that have broken off flush with the metal surface. Lay a nut the same internal diameter as the seized bolt in the centre of the broken bolt. Have ready the correct-size socket wrench for the nut. Hold the nut in place with a pair of needle-nose pliers. Work the wire weld on the inside of the nut. Weld the nut to the broken bolt. As soon as the nut changes from a bright orange colour to a dull grey or black, slip the socket wrench over the nut. Remove the nut in a counter clockwise direction. The welding not only heats the bolt and surrounding area, but also gives a solid grip to the broken fastener. It may take several attempts to remove the bolt. All of the above should be tried before the final action of a seized bolt extraction.
Drill and Easy Out
The final method that is employed for removing a seized broken bolt is drilling the bolt and using an easy out. Attention must be paid so that the correct-size drill bit is utilised. If the drill bit is too large, the internal threads will be damaged. Using a drill bit that is too small will break the easy out device. Use a hand held grinder to flatten the surface of the bolt before drilling. Employ a centre punch with a large enough hammer so the drill can be started in the centre of the bolt. Use heavy amounts of penetrating oil when drilling the centre of the bolt and when using the easy out tool.