Sometimes the head of a screw becomes worn and becomes difficult to remove due to slippage between the screw head and the screwdriver bit. This how-to discusses how to get these difficult-to-remove screws out of whatever it is that they've gotten stuck in.
Step 1
Avoid making the problem worse. If the tool you are using is slipping, stop using it immediately. Further slippage will only continue to wear down the screw head and make it harder to remove. Definitely be sure you are going in the correct direction for removal, which is usually--but not always--counterclockwise ("righty tighty, lefty loosy"). Pressing down hard as you are unscrewing will help prevent slippage.
Step 2
Use a manual screwdriver rather than a power drill. You will be able to put more pressure on the back of the screwdriver (to increase friction) and to go more slowly. Not all drills are strong enough to exert as much torque as you need to remove a recalcitrant screw. Some chuckless drills will actually lose their grip on the screwdriver bit if you put too much torque on them (especially in the reverse direction).
Step 3
Get more torque with a socket wrench. If you need a lot of torque because you are hurting your hand or you are not getting results, the best tool is a socket wrench, a common part of many professional screwdriver sets. This allows you to get 6 inches or more of lever arm rather than the half-inch or so a screwdriver handle produces. This greatly increases the amount of torque you can put on the screw for a given amount of hand pressure.
Step 4
Use a screw extractor. The right tool for the job, assuming the screw head is worn but intact, is called a "screw extractor". This is essentially a screwdriver or screwdriver bit which has strong, rough metal threads right on the tip. These are intended to burrow into the metal of the screw head and get stuck there so you can put some torque on it.
- Use a screw extractor like a normal screwdriver to remove the screw. Be sure to go slowly, and press down hard enough to prevent slippage and engage the burrowing threads.
- If the screw extractor can't get a grip, you may need to drill a small hole into the screw head. You will need a drill bit that is designed for drilling metal; a wood-drilling bit won't survive. Be careful! If you drill too far, you will destroy the head entirely or make it fragile enough that it will snap off, making it even harder to get the screw out. Given the nature of what you are drilling, pieces of metal may suddenly come flying out of the assembly, so wear eye protection!
- There is also a multi-spline type of screw extractor. The multi-spline extractor is like a hex nut with splines instead of threads on the inner bore. The multi-spline extractor fits over the head of the screw and over any projecting stud. The internal splines (teeth) engage the rounded head of the screw. Tap the extractor gently into place and turn it with a socket wrench. The multi-spline extractor is good for Torx and Allen head screws if the cylindrical body of the Allen screw is exposed. The multi-spline extractor is typically described as "Bolt extractor 5-piece set".
Step 5
Try a different screwdriver. If you don't have a screw extractor and don't want to try to get one just yet, you can try to use a different screwdriver or screwdriver bit. A screwdriver with a bigger head may help. Some screw heads can accept either a slot or a cross-head (e.g. Phillips) screwdriver. You may have some luck trying the other kind. If you have them in your screwdriver set, you might also try a Robertson (square), Allen (hexagonal), or Torx (six-pointed star) bit, depending on the shape of the hole you have. You may have some luck if you experiment with sizes.
Step 6
Tapping the screwdriver into place with a hammer may be helpful. Tap it with a hammer, but be careful and gentle as excessive force will destroy or remove the head of the screw.
Step 7
Drill out the entire screw as a last resort, and only if the screw is holding together metal objects. If all else fails, it is possible to drill out the existing screw with a power drill and bit of the same size as the screw's shaft. This will most likely remove the existing thread. Possible solutions at this point:
- Replace old screw with a self-tapping (thread-forming) screw of slightly larger size.
- Use a nut and bolt instead. If desired, weld the nut to one of the metal objects to create a stationary, threaded mount.
- If the screw was large enough, install a HeliCoil insert.
Step 8
Often placing a broad, flat rubber band between the screw and the screwdriver will yield good results if firm pressure and slow rotation is used. The rubber band acts to fill in the space that the screwdriver cannot grip.
