Washington, D.C. Centre
Tech-Tips
Home
About
Join
Board
Calendar
the Spark
Gallery
Tech-Tips
Regalia
Classifieds
Links
Contact

GET IT APART - PART II

By Jim Lunson, tech committee

 

Last month I went over some methods I have used to get stubborn bolts and screws on MG to come loose, all as part of changing out a worn part on the car and replacing it with a brand new one. There are a few more methods that can be tried in this pursuit, each with its benefits and drawbacks.

Excessive torque: One method of breaking loose a bolt that is frozen in place is the use of pry bars, or excessive torque as I like to call it. This is done by taking a normal wrench or socket set and by means of a pipe slipped over the handle end, greatly extending the length of the lever you have to pull against. This greatly increases the amount of torque you can put on a bolt. I have pipes of several diameters and lengths that I can slip put over most wrenches and handles... I call these my "persuaders" in getting a stubborn bolt to release. Remember the test results from the previous article on the force needed to free a rusted bolt. The first test required 516 lbs. of torque to work. This force is the equivalent of a 150 lb. person standing on the end of a wrench handle 3ft-5in long; a pretty strong piece of turning force in my opinion and not something you can get with a normal wrench. The extension gets this extra power. You have to keep in mind the limit of the socket or open-end wrench you are using as it can be easy to stress these items to where they snap off. You also need ample room to use this method. This method works very well on wheel lug nuts that were over-tightened by a mechanic changing tires or on parts that can be removed from the car and then disassembled on a bench. But this method has saved me in many instances where the increased torque is amazing in its ability to get bolts loose.

In looking at wrenches and wrench sockets keep in mind there are two types: six-point and twelve-point. The point number refers to the number of positions you can place a wrench over a bolt to get turning force. The advantage of the twelve-point is that you have twice as many places on the rotation circle to insert the wrench on the bolt. This is extremely important when working in tight spaces. The disadvantage is that the points are much shallower than the six-point style and when using excessive torque are more prone to either slip or round off the bolt head facets much faster than the six-point type. My socket wrenches, like most sets, are all twelve-point, but over time I have supplemented almost all the sizes with six-point sockets and try to use these whenever possible to take advantage of the greatly increased grabbing potential these offer. It makes a difference.

Impact wrenches: A great method of getting a stubborn bolt loose is the use of a pneumatic impact wrench. These devices apply at most only about 150 ft lbs of torque, but they exert this pressure at the rate of about 100 times a minute. This constant loading and unloading of torque on a stuck bolt is amazing in its ability to loosen even the most stubborn. The problem with this device is that not every home garage has a strong source of air pressure and the wrenches and sockets used with them are special (the sockets are blackened high carbon steel rather than the shinny steel found in most wrench sets and are always six-point). I usually use this method as a last resort. Then I go to my favorite repair shop and beg the mechanic to "hit a specific bolt" for a few seconds. This method was particularly successful in loosening the large bolts on the ends of the rear axles of my MG to change the rear bearings and seals. There, I had used every pipe I owned and was applying probably about 640 lbs of torque (160 lb @ 4 feet), all to no avail. My mechanic took about 10 seconds with his impact wrench to pop them loose. Retightened them by hand, drove home, and went to work.

Screw extractors:  These items look like regular drill bits only with a reverse spiral thread. The object here is to drill a hole in the bolt that will not come loose and insert this extractor. As the extractor penetrates the old bolt, it tightens against the sides of the hole and grabs the bolt. And being reversed threads, as you twist the extractor ever tighter, eventually it turns the bolt in the loosening direction. These bits sound like a good idea, but I have never had much luck with them personally. First, you have to make sure the hole you drill in the existing bolt is exactly centered and aligned with the bolt shaft. Otherwise, when the extractor is turned, it is applying pressure at an angle and not truly unscrewing the offending bolt. It then will not do the job. The other problem is that these bits are made of very strong steel and hence are rather brittle. If you do not turn the extractor exactly correctly, they have a tendency to snap off, leaving you with not only a bolt that is stuck, but now with a very hard steel shank in its center, making it very hard to drill out. Only when I have a good clear access to the offending bolt do I try this method.

Drilling & rethreading:  The final solution is to drill out the offending bolt or screw and replace it with a new one. This is difficult as it can often involve retapping the hole to restore the threads. Like the screw extractor step, drilling out a bolt on the car is very difficult due to space and viewing angles. I have found that to get a really rusted bolt out requires a drill almost the exact diameter of the bolt. I usually start with a small drill and then enlarge the hole, getting closer and closer to the bolt size as I go. Finally, at the correct size, the bolt will collapse inward, freeing itself from the hole or nut. However, often the drill is not centered or not directly into the bolt and ruined threads on the hole result. Sometimes the threads are so ruined that to regain the holding power, the hole needs to be enlarged and the next size up bolt threaded into the new hole. This is tough going, as the new part to be installed may not have a hole big enough for the new bolt, requiring drilling the part also. Again, this is the last resort and requires great care to get successful results.

These are a few ideas I have used over the years to free up bolts on the old car. Again, it is most frustrating to get a new part for our MGs and then spend the majority of time not on its installation but in removing the old part, usually due to a bolt or screw having been in place for so many years, and frozen so tightly that it seems it will never come apart. Hopefully, these ideas will speed up the process somewhat, making the task easier and certainly more enjoyable.

 

Back to Technical Tips

Home