If a screw cannot be loosened and is stuck, brute force rarely helps. This usually only damages the screw drive or the screw head is completely torn off. However, there are a few tips and tricks to solve a stuck screw that usually help and solve the problem.
There are many reasons why a screw cannot be loosened, therefore we must first determine why the screw is stuck.
1. Screw has a left-hand thread
2. Screw is rusty (corroded)
3. Screw head is round or the screw drive is damaged
4. Screw turns through empty
5. Screw is broken off
First you should check if it is a screw with a left hand thread. Left-hand threads are often used in automobiles, bicycles (e.g. pedals) or in sanitary areas. You can carefully try to loosen the screw in the opposite direction.
Creep oils are special oils which are very fluid and can penetrate into very small cracks and crevices via capillary action. Thus, the creep oil penetrates into the smallest gaps in screw connections and threads. One should however let the creep oil act for some time, so that it has time to penetrate into the gaps. The reaction time can take several hours, depending on the workpiece and the screw connection.
Blow on the head
Often, a few blows to the head of the screw are the puzzle solution. The vibration loosens the rust a little and the screw loosens and can be solved. You have to be careful not to damage the screw head.
Heat can also be an aid to loosen stuck screws. The affected screw is heated with a Bunsen burner or hot air dryer. This often helps with stuck screws that are rusted. Due to the high temperature, the material of the screw expands and when it cools down, the material contracts again.
After the screws have cooled down, creep oil can also be used. But be careful, if the workpiece or screw is heated too much, the material properties can change and the metal can become brittle. Heated screws should always be replaced by new screws after loosening.
With cross-slotted head screws, the use of a preserving rubber placed between the screw drive and screwdriver can significantly increase the force transfer. However, you should try very calmly and slowly to screw in the damaged screw.
With slotted screws you can cut another slot with a drill grinder or a saw crosswise to the existing damaged slot to loosen the screw.
With a round hexagon screw there are several possibilities.
If the screw is turning empty, the thread is severely damaged. There are several ways to loosen the screw. First you try to get under the head of the screw with a small screwdriver to lever the screw up, at the same time you try to carefully unscrew the screw.
Another possibility is to press it on the underside of the screw, so that it is pressed out of the thread. Once the screw is removed, the damaged thread can be repaired with a thread repair set. Instructions can be found here.
You can loosen broken or totally destroyed screws with an internal multi-tooth bit (Torx). To do this, drill a hole in the middle of the screw. In this hole an inner serrated bit (Torx) is inserted as a press fit. It is important that the hole is not too big or too small, it should be about half the thread diameter of the screw and be suitable for a bit. Now you can turn out the rest of the screw with the inner serrated bit (Torx). Please note that the used bit will be destroyed.
If it is not possible to loosen the screw shaft or the thread is destroyed, only a thread repair set can help. You can buy a cheap thread repair set Gewindereparatur Set können here.
Here, tools to loosen screws: