Loosening rusted screw connections
Before applying a wrench to a rusted nut or bolt, clean the exposed part of the thread from dirt and rust, otherwise the bolt will twist when unscrewed.
- Clean the threads with a wire brush, then spray them with rust remover.
- In the case of a fast-acting agent, unscrew the nut immediately. Otherwise, wait some time before unscrewing the nut.
Loosening damaged nuts
If the edges of the nut have already rounded from previous attempts to loosen it, or if rust has deformed the surface to which the wrench is applied, then the nut can only be loosened by force.
- As a first option, gripping pliers can be used. The pliers allow you to firmly grasp the nut and then unscrew it.
- If the pliers do not help, try gouging the nut with a chisel.
- If the nut is easy to approach, then it can be sawn along the thread with a metal saw. In workshops, a special tool for breaking nuts is used to remove such nuts.
Handling self-locking nuts
Self-locking nuts are tightly fastened to the threads, they do not loosen even with vibration. To do this, self-locking nuts have a plastic insert or a more tightly cut thread. Such nuts can only be used once, otherwise the self-locking properties of the nut are lost.
Loosening hexagon socket or multi-tooth screws
When loosening screws of both types, before using the appropriate tool, you must clean the hole in the screw head from dirt.
- Interchangeable socket heads are best for unscrewing these screws.
- Unlike conventional bent wrenches (when using which the force always acts at a certain angle) sockets withstand hammer blows from the square adapter side. By hitting the tool with a hammer or, in extreme cases, directly on the head of the screw, you can loosen the screw a little, this makes it easier to unscrew it.
Loosening slotted or Phillips screws
After a relatively short time, the screws can be so tight that it becomes impossible to remove them with a single screwdriver. Removing cross-slotted screws is further complicated by the fact that the screwdriver slips out of the slot even when the handle is pressed hard. After several unsuccessful attempts to loosen the screw, the Phillips slot is damaged, after which it is almost impossible to remove the screw.
- If the screw does not come out immediately, put a suitable, sturdy screwdriver on it and try to loosen it by hitting hard on the end of the screwdriver handle with a hammer.
- In most cases, the screw, which often rusts only in the head area, is knocked off, after which it can usually be unscrewed in the usual way.
- If that doesn't work, get an impact driver. With each impact on the top of the screwdriver handle, the pressure screwdriver rotates the interchangeable socket slightly. In this way, you can unscrew almost any screw.
Drilling self-tapping screws
If the head of the screw is in such a state that it is practically impossible to use the tool, then the screw can only be drilled out.
- First, use an appropriately sized drill to remove the head of the screw. If necessary, first drill the hole with a smaller diameter drill bit.
- After that, the threaded part of the self-tapping screw can either be pushed in or pulled out from the back with tongs.
- Otherwise, drill out the threaded part with a thin drill. If you select a drill bit that is too large in diameter, the screw hole will be large enough to fit only a thick self-tapping screw.
Screw falls off tool
If you need to screw in a screw again in a hard-to-reach place, you can prevent the screw from falling off the tool using the following simple trick: stick a small piece of chewing gum to the slot or stick the screw to the tool with adhesive tape.
Loosening and screwing in spacer pins
Since stud bolts do not have a surface to which a wrench can be applied, the surface must first be created.
- Screw tightly onto the free threaded part of the stud (hide) two nuts. Attach a wrench to these nuts and loosen or tighten the stud.
Drilling screws with loose heads
The mating thread in which the head screw sticks out should be damaged as little as possible.
- With a center punch, strike exactly in the middle of the remaining part of the screw.
- Now you can drill. For screw sizes up to M8, this can be done immediately with a tap drill. This is the diameter «shaved» screws, i.e. without thread flank. For screw sizes up to MB, the rule of thumb applies: The diameter of the drill bit for the tap hole must be equal to the diameter of the thread multiplied by 0.8. For example: thread M 6 x 0.8 = thread hole diameter 4.8. For screws with size M8 and larger, the body of the screw must first be drilled with a smaller diameter drill bit.
- The metal that remains in the threads of the thread can sometimes be removed with a scriber, but in most cases the thread has to be driven with a tap.
Thread cutting
Threads cut in light metal are especially easily broken, since in this case the material is not as hard as, for example, steel. If there is a lot of metal left, then you can cut a thread of a larger diameter. Otherwise, a threaded bushing will have to be inserted, but this work, of course, should be left to the workshop. Thread cutting and threading with a tap is carried out in three stages. Therefore, the corresponding taps are called as follows: draft (one ring on the stem), semi-finishing (two rings) and finishing (three rings or no rings) tap.
- Three taps are screwed in and then screwed out again, while the overdrilled hole is constantly lubricated with oil.
- In order not to break the tap, when screwing in the tap, it constantly needs to be turned back a little, otherwise the metal chips become too long and stick.
Screw size and tightening torque
If screws and nuts are not subjected to special loads, they are tightened using standard torques. Hobbyists usually tighten screw connections by instinct. So that you can use your torque wrench to check your instinct when tightening screws and nuts, we give the torque values \u200b\u200bfor the most commonly used screw connections:
Thread diameter (mm) | 6 | 8 | 10 | 12 | 14 |
Torque (N·m) * | 10 | 25 | 49 | 85 | 135 |
* The torques shown do not apply to special screws or screws that are driven into light metal.
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