see also Torques and sequence of tightening the cylinder head bolts for the K7M engine and for K4M
Universal tightening torque values based on fastener dimensions
Most fasteners must be tightened to a specific torque. Torque is the rotational force applied to a threaded part - a nut or bolt. Overtightening a fastener can loosen it and cause breakage, while undertightening can eventually loosen it. Bolts, screws and studs, depending on the material from which they are made and the diameter of their threads, have certain tightening torques, many of which are given in the technical data. Follow these guidelines carefully. For fasteners for which no tightening torques are given, a general torque table is provided here as a guide. These tightening torques refer to dry (unlubricated) fasteners screwed into steel or cast iron (but not in aluminum). As mentioned earlier, the size and strength class of a fastener determines the tightening torque that can be safely applied to it. The figures given here refer to class 2 and 3 fasteners. Fasteners of higher strength classes can withstand higher tightening torques
Metric thread size | Nm |
M6 | 9-12 |
M8 | 19-28 |
M10 | 38-54 |
M12 | 68-96 |
M14 | 109-154 |
Pipe Thread Sizes | Nm |
1/8 | 7-10 |
1/4 | 17-24 |
3/8 | 30-44 |
1/2 | 34-47 |
How to tighten
If the fasteners are installed in a certain order, loosen and tighten them in a certain sequence to prevent the part from tilting. Where this sequence is relevant, it will be shown.
If a particular bolt order is not important, use the following rule to prevent misalignment:
First, install the bolts or nuts and tighten them with your fingers. Then, tighten each one one full turn in a criss-cross or diagonal pattern. Then, return to the first part, and in the same sequence, tighten them still by half a turn. Finally, tighten each of them a quarter of a turn until each part of the fastener is tightened to the required torque. To loosen and remove fasteners, reverse this procedure.
To fix the thread, if necessary, use special compounds (anaerobic fixatives) for threaded connections.
What fixes threaded connections
1 Grover. This is a spring split washer used as a locking element. Growers should not be used on deformable materials such as aluminum and its alloys, as well as on copper or bronze.
2 Polymer insert. A sleeve is inserted into a special groove, which is deformed when the nut is screwed onto the thread. Once tightened, the polymer insert increases friction, preventing possible loosening of the joint from shaking. The disadvantage of such fasteners is the limited number of assembly / disassembly operations.
3 Fold washer. Such washers are usually made of mild steel and provided with paws. One of the legs is bent to the edge of the nut, which must be fixed from unscrewing, and the other is fixed, if possible, on the part to be tightened. It is clear that such parts are disposable.
4 Glue or cosmetic varnish. Of the improvised means for thread locking, nail polish or glue is often used. The main advantage of such techniques is simplicity and confidence that it will not get worse. But these drugs do not work for their intended purpose, so you should not expect serious protection from them.
5 cotter pin. A metal rod is inserted into a through hole and its ends are bent. While the cotter pin is in place, the nut will not loosen. It is clear that cotter pins can only be used with special nuts and bolts that have a hole. In addition, they will not help to fix the bolt or stud in the body of the part.
Nut with locking shoulder. Those who dealt with the front hubs of the Zhiguli probably remember a large nut, in which a thin shoulder should have been bent in two places into the grooves of the trunnion. The disadvantage of this solution is the need for a special part such as a bolt and a rather rare nut.
Locknut. The most primitive solution in the fight against self-loosening is locknuts. An additional nut is pressed against the main one and locks it. Such a solution cannot be used everywhere - sufficient space is required on the threaded part of the stud or bolt.