Removing corroded bolts and nuts.
Threaded connections.
Baked or broken screws have already discouraged many amateur mechanics from working on the car on their own.. A few tips should help novice hobbyists cope with such situations.
Unscrewing corroded screws.
Before you pick up a wrench or screwdriver, remove rust and debris from available thread coils. Otherwise, the strongly rusty thread may be broken.
■ Clean the thread coils with a wire brush and spray with a rust remover.
■ Using a quick-acting rust remover, start unscrewing the nut immediately.
■ For other rust removers, wait a while.
Unscrewing damaged nuts.
When the edges of the nuts have been "rounded” either deformed by corrosion and the key becomes unusable, then force must be used.
■ The first option is to use a self-clamping pliers. You can firmly grip the nut with them and even unscrew most of them.
■ When this method fails, cut the nut with a sharp cutter.
■ Having good access to the nut, it can be cut with a hacksaw. Car repair shops have special tools to unscrew damaged nuts.
Undoing screws with hexagon socket or Phillips socket in the head.
In both cases, first thoroughly clean the socket in the screw head.
■ It is best to use an attachment with a suitable hexagon or spline.
■ Unlike foldable keys (where the force is applied diagonally), using the socket allows you to hit the tool on the side of the square adapter with a hammer (even directly into the bolt if necessary). This should slightly loosen the connection and make it easier to unscrew the screw.
Loosening the screws with normal and cross slots.
Often, after a short time, it is impossible to unscrew the screws with an ordinary screwdriver. In the case of screws with a cross cut, even a strong pressure of the screwdriver does not prevent it from slipping out of the socket. After several attempts, the grooves are damaged, and the screw cannot be unscrewed.
■ When such a screw cannot be unscrewed, then select the star tip carefully and try to loosen the connection with strong hammer blows on the screw head.
■ This treatment generally helps, when only the screw head is corroded.
■ If, however, an attempt is unsuccessful, it is necessary to use an impact wrench. During each hit of the hammer on the handle, the tool rotates slightly and I manage to remove each screw.
Handling of self-locking nuts.
Nuts of this type tightly tighten on the thread and do not loosen even under the influence of vibrations. This is possible thanks to a plastic insert or a fine thread. These nuts are not reused, because after unscrewing they lose their self-securing properties.
The screw falls out of the tool.
If you are trying to put a screw in a hard-to-reach place and cannot hold it in the tool, then a simple procedure helps. Put some chewing gum into the screw groove, or attach it to the screwdriver with adhesive tape.
Reaming sheet metal screws.
When the screw head can no longer be turned by any tool, then you have to drill it out.
■ First, remove the screw head with a drill bit of appropriate thickness, or use a smaller drill bit to drill a screw.
■ The threaded part of the screw can now be pushed out with a drift, or pull out the other side with pliers.
■ In case of trouble, open the threaded part of the screw with a thin drill bit. Using a drill bit that is too large will enlarge the hole in the sheet and you will need to use a new screw with a larger diameter.
Loosening and tightening the studs.
Stud bolt (also called a pin) neither can be gripped with a key, or a screwdriver. You must first adapt it to this.
■ To do this, put two nuts on the bolt and tighten them in the opposite direction (to counter). Now you can use a flat spanner and screw in or remove the screw.
Reaming broken screws.
Try to protect the thread of the hole, the broken screw is screwed into it,
■ Use a center punch to mark exactly the center of the broken bolt.
■ Now you can start drilling: for holes up to M8 use a special reaming drill. It has the size of a screw core without thread. Is it 80% screw diameter; e.g.. M6 x 0,8 = 4,8 mm. For bolts above M8, the diameter of the countersink bit will be comparatively even smaller,
■ Metal residues in the threaded threads can sometimes be removed with a needle. Usually, however, a new thread has to be cut.
Thread cutting.
The thread cut in the light alloy component is particularly prone to breakage, because such a material has less strength than steel. if there is enough space, you can cut a new one, larger thread. Otherwise, drive a threaded sleeve into the hole, but this is already a job for the workshop. Correcting or cutting a new thread takes place in three stages using successive taps: Pre (marked with one strip on the shaft), Essential (two stripes) and final (three stripes).
■ Screw these three taps in and out of the drilled hole several times in succession, dropping a few drops of oil into it.
■ To prevent the tap from breaking, it should be slightly twisted out from time to time, to break off the metal shavings, that would be too long and cause the tap to jam in the hole.
Tightening bolts and nuts.
Bolts and nuts that do not bear excessive loads are tightened with standard torques. Most amateur mechanics do this by feel. If you have a torque wrench, pay attention to the guidelines below:
Thread diameter (mm) 6 8 10 12 14
Tightening torque (Nm)* 10 25 49 85 135
* The given values do not apply to special screws and screws screwed into elements made of light metal alloys.
