Circular saw

A circular saw is a power-saw using a toothed or abrasive disc or blade to cut different materials using a rotary motion spinning around an arbor. A hole saw and ring saw also use a rotary motion but are different from a circular saw. Circular saws may also be loosely used for the blade itself. Circular saws were invented in the late 18th century and were in common use in sawmills in the United States by the middle of the 19th century.The circular saw was invented around the end of the 18th century as a rip-saw to convert logs into lumber in sawmills and various claims have been made as to who invented the circular saw. Before the design was invented logs were sawn by hand using a pit saw or using powered saws in a sawmill using an up-and-down saw with a reciprocating motion. The rotary nature of the circular saw requires more power to operate but cuts faster because the teeth are in constant motion. The sound of the circular saw is different from the sound of an up-and-down saw and earned it the nickname buzz-saw.Typically, the material to be cut is securely clamped or held in a vise, and the saw is advanced slowly across it. In variants such as the table saw, the saw is fixed and the material to be cut is slowly moved into the saw blade. As each tooth in the blade strikes the material, it makes a small chip. The teeth guide the chip out of the workpiece, preventing it from binding the blade.In addition to hand-held circular saws (see below), different saws that use circular saw blades include:Originally, circular saws in mills had smaller blades and were used to resaw lumber after it passed through an 'up and down' (muley or sash) saw leaving both vertical and circular saw marks on different sides of the same piece. These saws made it more efficient to cut small pieces such as lath.After 1813 or 1822 saw mills use large circular saws, up to 3 meters (9 ft) in diameter. Large saws demand more power than up-and-down saws and did not become practical for sawing timbers until they were powered by steam engines. They are either left or right-handed, depending on which side of the blade the plank falls away from. Benching determines which hand the saw is. Saws of this size typically have a shear pin hole, off axis, that breaks if the saw is overloaded and allows the saw to spin free. The most common version is the ITCO (insert tooth cut-off) which has replaceable teeth. Sawmill blades are also used as an alternative to a radial arm saw.Cordwood saws, also called buzz saws in some locales, use blade of a similar size to sawmills. Where a sawmill rips (cuts with the grain) a cordwood saw crosscuts (cuts across the grain). Cordwood saws can have a blade from 20 inches (51 cm) to more than 36 inches (91 cm) diameter depending on the power source and intended purpose. Cordwood saws are used to cut logs and slabs (sawmill waste) into firewood. The Cord (unit) is the standard measurement of standing timber (by estimation) or rough logs. 'Cordwood' means unsplit logs four feet long. In the nineteenth and early twentieth centuries, farmers would supply householders in town with cordwood, which would then be re-sawn and split to a length and circumference suitable for woodburning heaters and ranges. Almost all these devices were designed to accept 16-inch sticks, conveniently a piece of cordwood cut into three equal lengths. Once a piece of cordwood had been re-sawn to three 16-inch pieces, it could easily be split to stovewood size with an ax.In woodworking the term circular saw is most commonly used to refer to a hand-held, electric circular saw designed for cutting wood, but may be used for cutting other materials with different blades. Circular saws can be either left or right-handed, depending on the side of the blade where the motor sits. A left-handed saw is typically easier to use if held in the right hand, and contrariwise for the right-handed saw, because the user does not need to lean across the saw to see the cutting line.Cold saw(ing) machines are circular saws that are used in many metal cutting operations. The saw blades used are quite large in diameter and operate at low rotational speeds, and linear feeds. There are three common types of blades used in circular saws; solid-tooth, segmental tooth, and the carbide inserted-tooth. The circular saw is typically fed into the workpiece horizontally, and as the saw advances into the material, it severs the material by producing narrow slots. The material is usually held in place during the cutting operation by means of a vise. The chips produced by cutting are carried away from the material by both the teeth of the blade as well as the coolant or other cutting fluid used.The rotary motion of a circular saw lends itself to cutting hard materials like concrete, asphalt, metal, tile, brick, and stone with an abrasive saws like a tile saw. Diamond blades and cut off wheels are commonly used in these applications.