One of the most frustrating problems during a repair job or assembly project occurs whenever the head of a screw becomes too worn or too damaged to accept a screwdriver. This type of damage is known as a stripped screw, and it usually means the screw cannot be driven in or twisted out of the project. The slot on the top of the screw head has become hopelessly bent, making it nearly impossible for a standard screwdriver to extract or tighten it. Fortunately, there are several workable solutions to the problem of removing a stripped screw.
One way to unscrew a stripped screw is to use a hammer to gently tap a different screwdriver into the damaged screw head. The new screwdriver may get enough grip to back the screw out if the user applies enough downward force and a counterclockwise twist. A power tool such as a drill does not offer any mechanical advantage, so it may be best to stick with manual tools. If the tapped-in screwdriver does not work with a Philips or cross-threaded screw, a small hole can be bored through the center of the screw head to create a deeper slot for a screwdriver.
If the screw has a flat slot, a rotary tool fitted with a metal cutting saw blade could be used to create a new slot. The stripped screw should then be easily removed with a standard flat screwdriver. The screwdriver should be held in the new slot with significant downward pressure and slowly twisted in a counterclockwise direction until it is fully removed. Even a stripped screw with a Philips or cross-threaded screw head can be removed using this method.
Sometimes there is enough of the main screw exposed to use clamping devices such as vice grips, pliers or adjustable wrenches. The clamping tool should be tightened around the damaged screw head or exposed screw shaft and turned in a counterclockwise direction until it is fully removed. This method is not always reliable, since the clamping tool may not be able to grip enough of the screw to provide sufficient torque or twisting power. The tool may simply spin in place around the shaft, or the screw could snap under pressure.
There are commercial products available which are designed specifically to unscrew stripped screws. One such product is a special drill bit with a reamer on one end and a screw remover on the other. In this case, a power tool such as a cordless drill can and should be used. The reamer bit drills out a small conical hole in the damaged screw head, while the screw removing bit digs into the sides of that hole and pulls the screw out.
A stripped screw can sometimes be hammered into the project forcibly, although there is a considerable risk of permanent damage and a weakened juncture. The entire screw could be drilled out completely with a metal-cutting drill bit on a power tool, but other options should be considered first. Sometimes a welder can attach a new screw head to a stripped screw, allowing it to be pulled out with a standard screwdriver later. It may also be possible to address a stripped screw from the opposite end if it has become exposed.