Removing rusted fasteners
Before using a wrench on a rusted nut or bolt, remove any dirt from any visible loose threads on the bolt. Clean the free part of the thread with a wire brush and treat with a rust remover. If you are using a quick acting rust remover, you can start loosening the nuts right away. If you are using a conventional neutralizer, you should wait a while before you start unscrewing the rusted fasteners.
The self-locking nuts sit firmly on the thread and do not loosen even due to vibration. To do this, they have inserts made of artificial material or a narrow thread. In general, self-locking nuts are used once, otherwise the effect of their action is lost, so always replace the removed self-locking nuts with new ones.
Loosening damaged nuts
If you knocked down the edges of the nut or they are badly damaged by corrosion, then only force will help you unscrew them. Try the following:
- unscrew the nut, firmly grasping it with adjustable pliers (gas key);
- if adjustable pliers do not help, use a sharp chisel and split the nut;
- if convenient, cut the threaded nut with a hacksaw;
- if there is sufficient space near the nut, use a nut splitter. The tool bolt is tightened until the nut splits. The advantage of this method is that the thread of the bolt is not damaged;
- use the so-called «fenders», which are used to loosen nuts at stations.
Loosening hexagon head bolts and «star»
Remove dirt from the bolt slots before inserting the appropriate wrenches.
It is best to use long 6-sided or, respectively, «stellate» heads. As opposed to conventional open end wrenches (in which the force is always applied to two faces of the bolt) push-on heads transmit force to all faces. Hitting a tool with a hammer (or, in extreme cases, directly on the head of the bolt) slightly loosen the bolt seat, which will make it easier for you to unscrew it. A hammer with a head made of copper or artificial material does not damage the part, but acts on the bolt, just like a normal hammer.
Work in hard-to-reach places
If you need to install and tighten a bolt in a hard-to-reach place, use the following methods. To prevent the bolt from falling out of the tool, stick a little chewing gum or grease on the head of the bolt and insert it into the slot of the key or attach the bolt to the tool with adhesive tape.
Loosening slotted and Phillips screws
After some time, the screws can rust so badly that they can no longer be removed with a simple screwdriver. With cross screws, even if the screwdriver is not pressed very hard, after numerous attempts, it is possible to spoil the cross slots so that it will be impossible to unscrew the screw.
If the screw cannot be removed immediately, do the following:
- Take a sturdy screwdriver that exactly matches the size of the screw and try to loosen the screw connection with a strong hammer blow on the end of the screwdriver handle. Often the screw is heavily corroded only at the head, so after being hit with a hammer it can be easily turned out;
- if that doesn't help, use an impact screwdriver. After each blow with a hammer on the back side of the handle of the impact screwdriver, its working part is rotated. This tool allows you to remove almost any screw.
Removing fasteners by drilling
If the bolt or nut cannot be unscrewed using the above methods, then only drilling will help, which is carried out as follows:
- Use a large drill to drill out the head of the bolt. If necessary, before this, a preparatory hole can be drilled in the center of the bolt head with a small drill;
- either knock out the remaining threaded part or remove it with pliers;
- if this fails, carefully drill through the threaded part with a bit less than the nominal value of the corresponding thread, and remove the remaining metal from the counterpart.
Unscrewing the studs
Since the studs cannot be unscrewed with ordinary tools, proceed as follows:
- on the free threaded part of the stud, very tightly screw two nuts one after the other (hide);
- grasp the lower nut with a wrench and unscrew it together with the stud.
Drilling bolts with sheared heads
The thread in which the sheared bolt sits should, if possible, not be damaged, for which:
- bolt the center of the rest of the bolt;
- now you can start drilling. Bolts up to size M8 can be drilled with a tap drill (is the bolt body diameter without thread). For bolts up to M6, the rule of thumb applies: multiply the thread diameter by 0.8. For example: threaded connection M6x0.8 = threaded hole diameter = 4.8 mm. Bolts from M8 should be pre-drilled with a thinner drill;
- remove metal particles remaining in the thread with a scriber. However, in most cases it will be necessary to re-thread the thread.
Thread cutting
Threads cut in light metal break out especially easily, since its strength is not as high as that of steel. If there is enough metal, you can make a thread with a larger diameter. Otherwise, a threaded sleeve should be used - this work is carried out at a car service.
Thread cutting is performed in three stages using the corresponding taps 1, 2 and 3 of the number. When performing this work, constantly lubricate the threaded hole with oil. in order not to knock down the thread, you need to cut it carefully, applying a slight axial force to the tap, periodically turning it out and then screwing it deeper. Upon completion of work, clean the threads of remaining metal chips and additives.
Fastener dimensions and tightening torques
Bolts and nuts that do not require special tightening requirements are screwed with a standard torque, which depends on the diameter of the bolt thread (nuts). Most amateur mechanics spin them «to the touch». The dependence of the tightening torque on the thread diameter is as follows:
| Thread diameter, mm | 6 | 8 | 10 | 12 | 14 |
| Tightening torque, Nm* | 10 | 25 | 49 | 85 | 135 |
* The values given do not correspond to the tightening torques of special fasteners and fasteners used for light alloys.