Removing Studs

What are the most common problems with removing bolts/studs that are difficult to remove?

1. corrosion (rust or other oxidation)
2. thread sealant
3. cross-threaded

On older engines, particularly those with cast iron block and iron or steel bolts (a) is going to be the most common. The rust locks the bolt/stud threads fast in the hole. In its early stages, you will be able to shock the bolt and break the rust. In its later stages the base metal of the bolt/stud and the block will have become partially fused together. Once this has occurred only heat will resolve the problem.

With a newer engine where the metal in the block is usually different than the metal in the bolts and studs eg. aluminum/aluminium block corrosion is less of an issue. It does occur, but only shock will be required to break the bond because the dissimilar metals will not fuse.

The second issue which is becomming more common is the usage of thread lock sealants such as Loctite (R). In my restoration of old stationary farm engines I will not use thread sealant preferring to remain faithful to the methods of the time, but with a modern engine there is often no other choice. Thread lock sealants fall into two basic groups, removable and permanent. Removable as its name suggests will allow the bolt/stud to be removed using only force or shock. Permanent will usually require heating.

The final issue is due to carelessness of the last person to work on the bolt/stud. Cross-threading occurs when the threads on the bolt/stud are not quite lined up with the the threads in the hole. This is usually indicated by the bolt/stud being hard to turn on insertion. A careless or unaware person will apply force to screw the bolt/stud home. It should be backed out and inspected then reinserted correctly. It may be necessary to chase the threads in the hole and on the bolt/stud to clean them up. Some people advocate turning the bolt/stud 1/4 turn counter-clockwise then screwing home clockwise as this is supposed to help the threads "find each other".

I've read of several different techniques for removing bolts with heat: what are the differences between heating and heat then cooling them?

What is the best method to remove stubborn bolts/studs without using heat?

Your best tool is patience, if at first a bolt or stud will not move, soak and whack it some more and leave it for a time. Too much force will break even a good stud.

Bolts

Studs

I don't usually plug brands, but the best tool I've come across for the removal of studs is the Sears Craftsman eccentric stud removal tool. This tool comprises a rotating disk and a tool body. The tool body is placed over the stud, and a 1/2" drive socket handle is used to turn the whole tool. The eccentric disk within the tool locks the tool onto the stud. Once locked, the further turns of the socket handle turn the stud. I have found that once the stud moves, the tool should be backed off and the process restarted or you end up with the stud stuck within the tool! This tool combined with a 3' breaker bar and an initial heat treatment has not failed me to date on studs which are in reasonable condition.

If you do not have such a tool and want to reuse the stud, locate two substantial nuts which will fit on the stud. Screw the first on by hand leaving enough threads exposed for the second. Then screw on the second. Apply a spanner/wrench to each. Twist the bottom nut counter-clockwise (upwards) and the top nut clockwise (downwards) until they lock together and cannot be turned further. Now use a spanner/wrench on the bottom nut to twist out the stud.

Poor Condition Studs

If the broken stud is protruding enough to get the removal tool onto it, then reapply the tool and finish the removal.

If the broken stud is protruding slightly, weld an oversize nut onto the stud and twist it out with a socket spanner/wrench. Obtain as much weld fusion as possible, MIG or TIG will give better results than Gas or Arc. Use a thin wire or rod so that the weld metal penetrates between the nut and the stud.

If the stud has broken below the surface there are two possible methods. You can either drill out the stud using a drill bit which removes the stud metal but leaves the threads to be picked out later with a dental pick. An old fashioned tool which sadly has no modern replacement will come in very handy here. The Chicago Flexible Shaft company (now known as Cooper Tools) once made a magic tool called a Cole Drill. The unit bolted to the work using the exising stud holes, or even the studs themselves and could be positioned exactly to drill out the stud without ruining the threads in the hole. The modern version using a magnetic base is in my opinion useless. You can occasionally pick up a Cole Drill on Ebay.

The final removal method for studs broken below the surface is not one I've tried myself, but I know that it can be used if you have the right equipment and skill. Using a plasma torch the stud can be burnt out of the hole, apparently without damage to the threads within the hole. This method is out of reach of the average home workshop, but can be replaced by burning the stud with an arc welder.

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The above is the transcript of an interview I did with Brendan Baker of Engine Builder Magazine, the questions are Brendan's and the answers are mine.

thanks for your help!


Brendan Baker
Managing Editor
Engine Builder Magazine
bbaker@babcox.com
ph. 330.670.1234 x.228

Another method by Roland Craven - heating

Further information on Stud Removal