A screw that has been subjected to wear, nicks and other damage, or rusting can be difficult to remove. If the threads have been degraded or stripped off entirely, the fastener may not respond to standard insertion and removal methods, requiring an alternate strategy for addressing the problem. Exposure to a combination of water and oxygen can cause iron-oxide to form on metal screws, creating a rigid and non-reactive surface coating that deteriorates a fastener's functionality. Like stripped threads or screw damage, this corrosion-rust-can cause a component or machine to fail if the afflicted screw is not properly removed.
Removing a Stripped Screw
While it's possible to purchase a specialized stripped screw removal kit, in many cases the job can be accomplished using a standard set of tools. One of the major considerations in fastener removal involves slippage. It is important to apply leverage to move the damaged screw in a counterclockwise direction, but using insufficient force or an improperly sized tool can cause your grip to slip away. For this reason, a manual screwdriver can sometimes be better suited than a power drill, as it allows you to apply more pressure, and hence more friction, to rotate the screw without slipping. A socket wrench can also be used to apply additional torque because it provides more arm leverage than a screwdriver, increasing the amount of pressure applied from the same level of physical exertion.
A screwdriver that fails to gain leverage against the stripped screw can be tapped with a hammer to position it properly. If the screw head is damaged, a screw extractor, which features special tapered threads designed to dig into the screw to acquire torque, can be a helpful solution. The extractor can be handled like a standard screwdriver, but if it fails to catch a grip, it may be necessary to drill a hole directly into the screw shaft so the extractor threads can gain traction. When doing so, it is important not to drill too deeply, as that may destroy the head entirely or weaken it enough for it to detach.
Removing a Rusted Screw
A screw that is subjected to moisture for a prolonged period will begin to acquire rust at a rapid pace. This can make it as difficult to remove as a stripped screw, and can ultimately lead to degradation in the quality of the device in which the screw is inserted. If rust has corroded the threads or degraded the screw head, the fastener can be difficult to grip with a screwdriver or a wrench, requiring a different range of solutions than those effective for stripped screws. In cases of severe rusting, there are several available options, including:
o Cutting: If a rusted fastener can no longer be salvaged, cutting it out may be the last viable solution. A splitter, cut-off wheel, or powerful shears can be used to slice it, though they will make the screw unusable for future projects. Likewise, employing a vise-grip to pull off the screw head and remove it from the slot will permanently break the screw.
o Torching: A low-powered gas torch can often solve a rusted fastener problem. Sufficiently heating a screw may cause it to expand enough to be loosened from its slot. It is important, however, to follow safety precautions when employing a torch or any other mechanical device, especially because some screw lubricants or coatings are flammable and may ignite when put under a flame.
o Lubrication: Lubrication may be a simpler screw removal option, as it relies on relatively little equipment to succeed. Various kinds of industrial or commercial lubricants can penetrate to a fastener's threads. After apply a lubricant, tapping the screw head will help it pass through the fitting and reach the screw shaft, loosening the screw enough to be removed with pliers or a screwdriver.
