Buy Machine Screws Online: Screw Sizes

A machine screw is a small bolt designed to take a matching nut or fit into an insert fixed into wood, plastic or metal. Machine screws range from the very small to a ¼ inch in diameter, where they are generally referred to as machine bolts, although the defining line between the two is arbitrary.

Unlike bolts, machine screws usually have a standard screw head, such as slotted head or Phillips head, which is used to tighten the assembly. By contrast, bolts tightened via a nut, using an external driver or spanner.

Machine screws are available in a number of materials, including mild steel, stainless steel, brass, and nylon, with each type having its own unique set of advantages and disadvantages, suiting specific tasks and uses.

Machine Screws and Sizing

Machine screws are available in an enormous range of sizes, shapes, and styles. Despite standards ensuring that products made by different manufacturers will mate, there are still many differences, especially between metric machine screws and Imperial machine screws, with different terminologies used to describe thickness, length, grade, and thread coarseness.

Machine Screw Diameter

According to the American Standard, the diameter of the machine screw is given as a number from 0 to 10, with even screws gauges much more common than odd numbers. 12 and 14 are also available, but less common, and sizes greater than gauge 10 are often expressed as fractions of an inch.

Metric measurements of diameter are given in millimeters, and this is usually prefixed by an ‘M,’ to prevent confusion with the American Standard.