Screws are often the best way of fastening things toget […]
Screws are often the best way of fastening things together. The other two common methods nailing and gluing are often quicker and require less preparatory work but both produce a permanent joint which cannot readily be dismantled again, and neither method of fixing is likely to produce the strength and abuse resistance that screwed joints have.
A screw is a type of fastener used to join wood, metal, and composite materials. While nails have a smooth shank, screws feature a series of grooves, or threads, along the length of the shank. These threads bite into a material upon installing, helping to create a secure bond. Screw thread can be used to differentiate types of screws from one another, and also to determine where the screw should be used.
The screw thread on each unit may cover the entire shank, or just a portion. In general, a fully-threaded screw is designed for metal, while a partially-threaded one is designed for wood. Screw thread may be either right- or left-handed, and is determined by the direction that installers must turn the screw during installation. The majority are right-handed, and must be turned clockwise, but a few feature left-handed threads for special applications.
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.
One way to unscrew a trapezoid lead 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.