A hole saw also known as a hole cutter, is a circular saw

Saw

A saw is a tool that uses a hard blade or wire with an abrasive edge to cut through softer materials. The cutting edge of a saw is either a serrated blade or an abrasive...

 designed to cut through relatively thin workpieces. It is used in a drill

Drill

A drill or drill motor is a tool fitted with a cutting tool attachment or driving tool attachment, usually a drill bit or driver bit, used for drilling holes in various materials or fastening various materials together with the use of fasteners. The attachment is gripped by a chuck at one end of...

.

Construction

The saw consists of a metal cylinder, usually steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

, mounted on an arbor

Mandrel

A mandrel is one of the following:* an object used to shape machined work.* a tool component that grips or clamps materials to be machined.* a tool component that can be used to grip other moving tool components.- Variants :...

. The cutting edge either has saw teeth formed in it or industrial diamonds embedded in it. The arbor can carry a drill bit

Drill bit

Drill bits are cutting tools used to create cylindrical holes. Bits are held in a tool called a drill, which rotates them and provides torque and axial force to create the hole. Specialized bits are also available for non-cylindrical-shaped holes....

 to bore a centering hole. After the first few millimeters of cut, the centering mechanism may no longer be needed, although it will help the bit to bore without wandering in a deep hole. The sloping slots in the cylinder wall help carry the dust out. The kerf

Kerf

Kerf and similar can mean:* kerf, the width of a cut* Kerf, a poetry collection by Peter Sanger* Kerala E.N.T. Research Foundation , a hospital at Kollam in Kerala in India...

 of the cut is designed to be slightly larger than the diameter of the rest of the hole saw so that it does not get jammed in the hole.

Holes saws for use with portable drills are commonly available in diameters from 6 millimetre. The only limit on length of the cylinder, and thus depth of the hole, is the need to remove the bit from the hole to clear dust. A 300 mm (11.8 in) cylinder length is not uncommon, although shorter bits are usual. By breaking the core off from time to time and using a shank extension, a diamond core drill can drill to depths many times its length.

Saw teeth are used for most materials, such as wood

Wood

Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

, plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

, soft plaster

Plaster

Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...

, and metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

. Diamond hole saws are used to bore holes in brick

Brick

A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...

, concrete

Concrete

Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

, glass, and stone

Rock (geology)

In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

.

Adjustable

An adjustable hole saw 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.

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.

Advantages and disadvantages

The main advantage over conventional drill bits is the hole saw's efficiency, because very little of the total material being removed is actually cut, which ultimately reduces the overall power requirement. Another advantage over drill bits is the wider size capability.

Some disadvantages include:

• The portable drill used must be capable of producing considerable torque
  Torque
  Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
  
   at low speed
• They tend to bind if choked with dust, or if allowed to wander away from the central axis of the planned hole
• The kick-back from a powerful drill may be severe under some conditions, and long side-handles should be used, preferably with two operators for very large holes.

Wet or dry drilling

Diamond hole saws are also called diamond core drill bits. Laser welded diamond core drill bits can be used in wet and dry drilling, but not all materials to be drilled are suitable for dry drilling. Very hard materials like reinforced concrete

Reinforced concrete

Reinforced concrete is concrete in which reinforcement bars , reinforcement grids, plates or fibers have been incorporated to strengthen the concrete in tension. It was invented by French gardener Joseph Monier in 1849 and patented in 1867. The term Ferro Concrete refers only to concrete that is...

normally should be drilled with water, otherwise the excessive heat generated during the drilling process may cause the diamonds on the core bit to become blunt, and then lead to poor drilling performance.

The bond materials and the diamonds used on the laser welded diamond core drill bits usually are specially adjusted to fit the wet and dry drillings respectively. This can make the core bits perform better in drilling speed and/or lifespan.