A Screw Is a Shaft with a Helical Groove or Thread Formed on Its Surface

A screw is a shaft with a helical groove or thread formed on its surface and provision at one end to turn the screw. Its main uses are as a threaded fastener used to hold objects together, and as a simple machine used to translate torque into linear force. It can also be defined as an inclined plane wrapped around a shaft. Screws can normally be removed and reinserted without reducing their effectiveness. They have greater holding power than nails and permit disassembly and reuse. The vast majority of screws are tightened by clockwise rotation; We speak of a right-hand thread. Screws with left-hand threads are used in exceptional cases, when the screw is subject to anticlockwise forces that might undo a right-hand thread. Left-hand screws are used on rotating items such as the left-hand grinding wheel on a bench grinder or the left hand pedal on a bicycle (both looking towards the equipment) or hub nuts on the left side of some automobiles. Wood Screw: These screws are used in wood. The threads are usually coarse and deep to help them grab the wood. If you're like most people, wherever you store your tools you’ve got a bunch of tin coffee cans and plastic tubs filled with assorted screws, nails, nuts, bolts, and other miscellaneous bits of hardware. And whenever you need something—like a screw to tighten a loose deck board—you rummage through them looking for the one you need. But with their packaging gone, how do you tell what's what? The simplest way to tell screws apart is by colour. Any black ones you find are drywall screws, cheap and useful for many odd jobs, but not very strong. The colour is from a phosphate coating that prevents wet drywall compound from corroding the screw head. Blue ones are masonry screws, used for fastening things to brick, block, or rock, though you have to drill a pilot hole first. They would have come with the right sized bit in the package. Without it, you'll need to do a little trial-and-error to find a bit slightly narrower than the diameter of the screw threads. Golden-hued screws could be brass but are more likely brass-plated. They won’t rust, which makes them an attractive choice for boat fittings, but are significantly weaker than equally rustproof stainless steel. Brown or green ones are corrosion-resistant deck screws. But unless you bought them in the last year or so you'll need new ones. Pressure-treated (PT) lumber manufacturers recently changed the chemicals they use to a formulation that's extremely corrosive to the wrong hardware. If you're building with the new PT wood, buy fasteners labelled “ACQ compatible. ” The bulk of your pile is likely made up of shiny silver screws. The short, sharp-tipped ones with round heads and threads spiralling up the entire shaft are sheet metal screws (a. K. A. Self-tapping screws) that can bite into thin metal like aluminum eavestroughing. Any with blunt tips are machine screws, essentially threaded bolts that are tightened with a screwdriver. They’re commonly used in electrical work and to affix things like kitchen cabinet handles. Most of the ones you’ll be left with are wood screws, with coarse threads and a smooth section at the top of the shaft. Some will be made of corrosion-resistant stainless steel, and some of cheaper, everyday steel. You can’t tell them apart by sight but, luckily, there’s a simple trick to sorting them out. Grab a magnet and run it through the pile; Any that cling to the magnet are ordinary steel, the remaining ones are almost certainly stainless. Source: Globalfastenermarket. Com