The following reasons may explain why a screw breaks, turns through, or is stuck in the workpiece:
- is very old, rusted and therefore exhausted.
- has been broken off due to excessive tightening torque.
- is made of a soft material and was not suitable for the application.
- Manual drilling machine (if applicable box column drill)
- Left-hand cutting twist drill
- Penetrating oil (e.g. WD-40)
- Left-hand cutting hand tap
- Adjustable tap wrench
- Center punch
- (Cutting oil, when available)
Since the screw can only be turned to the left, you need left-hand cutting tools.
The diameter of the left-hand cutting twist drill should be max. half the diameter of the broken screw. If the screw has a diameter of 12 mm, the twist drill should have max. 6 mm.
In any case, you should use rust removers such as penetrating oil (e.g. WD-40) before processing. Rust remover loosen stuck screws and corroded metal connections.
The working procedure
The probably easiest way to turn a stucked screw out of a workpiece (e. g. structural steel) is to use a left-hand cutting twist drill. This applies, for example, in cases where the screw is hardly rusted but only broken off.
Following video is available for our left-hand cutting twist drill:
In this video you can see how easy it is to unscrew the broken screw.
If your broken screw is uneven, protrudes slightly and you can hardly center the drill bit in the screw, and/or you work with the hand drill, then
- level the surface with the file;
- use the center punch, by punching with the hammer a centering in the middle of the screw.
Drill the screw out with the left-hand cutting twist drill as shown in the video. If you have cutting oil at hand, use it here.
But what to do if the screw is more persistent and still can't get out?
Take the left-hand cutting tap and tighten it into the adjustable tap wrench. Turn the hand tap into the hole you have drilled in the screw.
It is important to turn the thread counterclockwise into the screw!
At some point, the friction between the screw and the drill becomes so strong that the screw loosens.
**When removing the screw, make sure that you do not damage the thread. If this should happen anyway, our article **"How do I repair a damaged thread in four steps?" will help you.
Rusty screw with head
If the screw is rusty, the following two tips can be used to loosen a screw with a head without much effort:
- Soak the screw with penetrating oil for a few days.
- Slight hammer on the bolt head. Due to the vibrations of the hits, the rust layer can crack and loosen the connection between workpiece and screw.
It can happen that you get a broken screw already loosened with penetrating oil and a left-hand cutting twist drill. If this is not the case, you can use a left-hand tap or even a left-hand extractor.
The online magazine diybook explains in its very helpful video how to use the left-hand extractor.
The professional screw extractor mentioned in the video is available as a 21-piece thread-extractor set in our range of products.