Hole saw

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52 mm holesaw made by Sandvik of Sweden circa 1988

A hole saw (also styled as holesaw) is a saw that is in the shape of a circle. It is used in a drill to cut large holes in reasonably thin material.

Holesaws have the same general mechanical construction as the diamond core drill bit, but, instead of the abrasive effect of diamonds, the holesaw uses the cutting effect of saw teeth. The open end of the saw's cylinder is milled with saw teeth. Instead of masonry, the holesaw is suitable for cutting wood, plastic, soft plaster or soft metal.

The placement of the saw teeth makes the cut annulus slightly wider than the cylinder wall thickness, so the cylinder doesn't rub in the cut. Just as in the diamond core drill bit, the cylinder is mounted on a mandrel — an arbor with a centre pilot drill — and has sloping slots to clear sawdust.

[edit] Adjustable holesaw

An adjustable holesaw consists of a number of thin metal saw blade-like strips, and a flat disc with a large number of grooves in one side and a shank on the other. By snapping the blades into different grooves on the disc, a hole saw of a wide variety of sizes can be constructed.

[edit] Circle cutter

Another type of adjustable hole saw, also called a circle cutter, is formed by having one, two, or three adjustable teeth on a platform with a pilot bit. To cut out a hole of any size, the teeth need only be adjusted to the proper position. This type is available in sizes up to a foot and larger, and can be used to accurately cut large circles.