Circular saw shell

Circular saw

The circular saw is a metal disc or blade with saw teeth on the edge as well as the machine that causes the disk to spin. It is a tool for cutting wood or other materials and may be hand-held or table-mounted. While today they are almost exclusively powered by electricity, larger ones, such as those in "saw mills", were traditionally powered by water turning a large wheel. Most of these saws are designed to cut wood but may be equipped with blades designed to cut masonry, plastics or metal although there are purpose-made circular saws specially designed for particular materials.

Invention

Various claims have been made as to who invented the circular saw:

  • A common claim is for a little known sailmaker named Samuel Miller of Southampton, England who obtained a patent in 1777 for a saw windmill. However the specification for this only mentions the form of the saw incidentally, probably indicating that it was not his invention.
  • Walter Taylor of Southampton had the blockmaking contract for Portsmouth Dockyard. In about 1762 he built a saw mill where he roughed out the blocks. This was replaced by another mill in 1781. Descriptions of his machinery there in the 1790s show that he had circular saws. Taylor patented two other improvements to blockmaking but not the circular saw. This suggests either that he did not invent it or that he published his invention without patenting it (which would mean it was no longer patentable).
  • Another claim is that it originated in Holland in the sixteenth or seventeenth century. This may be correct, but nothing more precise is known.
  • The use of a large circular saw in a saw mill is said to have been invented in 1813 by Tabitha Babbit, a Shaker spinster, who sought to ease the labour of the male sawyers in her community.

Types of circular saw

In addition to hand-held circular saws (see below), different saws that use circular saw blades include:

Sawmill blades

Saw mills use very large circular saws, up to nine feet (2.97 meters) in diameter. 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

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 to more than 36 inches diameter depending on the power source and intended purpose. Buzz saws are used to cut long logs (cordwood) and slabs (sawmill waste) into pieces suitable for home heating (firewood).

Most cordwood saws consist of a frame, blade, mandrel, cradle, and power source. The cradle is a tilting or sliding guide that holds logs during the cutting process. Some cordwood saws are run from a belt from a farm tractor power takeoff pulley. Others are equipped with small gasoline engines or even large electric motors as power sources. The mandrel is a shaft and set of bearings that support and transfer power to the blade. The frame is a structure that supports the cradle and blade at a convenient working height.

Cordwood saws were once very popular in rural America. They were used to cut smaller wood into firewood in an era when hand powered saws were the only other option. Logs too large for a cordwood saw were still cut by hand. Chainsaws have largely replaced cordwood saws for firewood preparation today. Still, some commercial firewood processors and others use cordwood saws to save wear and tear on their chainsaws. Most people consider cordwood saws unsafe and outdated technology.

Hand-held circular saws

The term circular saw is most commonly used to refer to a hand-held electric circular saw designed for cutting wood, which may be used less optimally for cutting other materials with the exchange of specific blades. Circular saws can be either left or right handed, depending on which side of the blade the motor sits.

Blades for timber are almost universally tungsten carbide tipped (TCT). High speed steel (HSS) blades are also available. The saw base can be adjusted for depth of cut. Adjusting the depth of cut helps minimize kickback. The saw base can also be adjusted to tilt up to 50 degrees in relation to the blade.

The saw can be designed for the blade to mount directly to the motor's driveshaft (known colloquially as a sidewinder), or be driven indirectly by a perpendicularly-mounted motor via worm gears, garnering considerably higher torque (Worm-drive saws).

The worm-drive portable circular saw was invented in 1924 by the Michel Electric Handsaw Company which renamed itself Skilsaw Inc., today a subsidiary of Robert Bosch GmbH. Portable circular saws are often still called Skilsaws or Skil saws. Its successor is still sold by Skil as the model 77. To get around the Skil patents, Art Emmons of Porter-Cable invented the direct-drive sidewinder saw in 1928. Recently smaller cordless circular saws with rechargeable batteries have become popular.

See also

References

External links

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