Screws

Screws are spiral grooved fasteners that are driven into place via a rotating motion. There are a variety of screw types including a stainless steel screw, lead screw, captive screw, set screw, self drilling screw, sheet metal screw, lag screw, brass screw, and concrete screw. There are many systems for specifying the dimensions of screws. The United States has its own system of non-metric screws called the unified threat standard, but in much of the world the metric screw has displaced many older systems. Common metric screw measurements include an M3 thread that has a 0.5 mm pitch, M4: 0.7 mm, M6: 1 mm, M10-12: 1.5 mm, M14-16: 2 mm, M18-22: 2.5 mm. The primary purpose of screws is to act as a threaded fastener used to hold objects together. Screws are also used as a simple machine to translate torque into linear force.

Varieties of screws serve specific purposes and are manufactured from a variety of materials. A stainless steel screw is heat treated, hardened steel primarily used for decks, log homes, remodeling, kitchen cabinets, docks, and roofing. Therefore, a stainless steel screw is primarily used as a wood screw. The most common stainless steel screw sizes are 1" - 14". A lead screw may also be produced from stainless steel, except 5 pitch lead screws which are electroless nickel plated, cold rolled steel. A lead screw is often utilized in manual and power drive applications. A captive screw is a threaded screw which is held captive to a panel and when it is disengaged from its main nut, it will remain attached to that panel. A set screw is used to prevent loosening due to vibration, are available with thumb screw, square head, Allen head, and, most commonly, headless. A set screw is designed to be inserted flush with or below the surface of a work piece. A self drilling screw has a drill-shaped point that will cut through a material so that pre-drilling is not required. A sheet metal screw is used for rapid and rigid fastening in materials as sheet metal to metal, plastics, plywood, aluminum, hard rubber and other comparable compositions. A lag screw is a large wood screw with a hexagonal head, driven by a wrench rather than a screwdriver. Brass is a surprisingly strong but very soft metal. A brass screw requires a carefully sized pilot hole to avoid installation breakage. A brass screw is the traditional choice for a non-corrosive metal. A concrete screw provides fast, secure anchoring, utilizing a hardened screw with specially fashioned high and low threads that cut into a properly sized hole and thread into concrete, masonry, brick, and block. Installation is accomplished through the use of specially designed carbide. A concrete screw eliminates the need for plastic or lead anchors in medium and light duty applications, and can be removed if desired without excessive damage to the surrounding surface that other screws may create. Screws are produced from many materials including stainless steel, titanium, bronze, brass, nylon, and teflon, porcelain, and glass.

Screws are utilized in construction, electrical line insulators, robotic drives, aircraft, automobiles, heavy trucks, and similar critical applications. The Unified Thread Standard (UTS) specifies the thread form, series, class, allowance, tolerance, and designation for unified screws. The standards by which screws are measured by are controlled by the American Society of Mechanical Engineers (ASME) and the American National Standards Institute (ANSI).

• What You Ought To Know About Ball Screws
  Whether the goal is high precision or low cost, ball screws are often the best option for linear actuation. Thomson Saginaw Ball Screw Co. Miniature ball screws are an efficient low-cost option for...
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• Lead Screw Technology Rolls Over Ball Screws
  Lead screws were once believed to be a cheap substitute for ball screws, to be used in less demanding applications. They were often assembled using low quality screws from ball screws or fastener...
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• Which Screw? Picking the Right Technology
  Many industrial linear motion systems employ a screw mechanism of some type to achieve a desired linear motion. The intention of this pamphlet is to supply an explanation of typical terminology used,...
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Part Numbers for Screws