A hole saw (also styled holesaw), also known as a hole cutter, is a saw blade of annular (ring) shape, whose annular

kerf A saw is a tool consisting of a tough blade, wire, or chain with a hard toothed edge. It is used to cut through material, very often wood, though sometimes metal or stone. The cut is made by placing the toothed edge against the material and mo ...

creates a hole in the

workpiece A workpiece is a piece, often made of a single material, that is being processed into another desired shape (such as building blocks). The workpiece is usually a piece of relatively rigid material such as wood, metal, plastic, or stone. After a ...

without having to cut up the core material. It is used in a

drill A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driver chuck. Hand-operated types are dramatically decreasing in popularity and cordless battery-powered ones proliferating due to ...

. Hole saws typically have a pilot drill bit (arbor) at their center to keep the saw teeth from walking. The fact that a hole saw creates the hole without needing to cut up the core often makes it preferable to twist drills or spade drills for relatively large holes (especially those larger than ). The same hole can be made faster and using less power. The depth to which a hole saw can cut is limited by the depth of its cup-like shape. Most hole saws have a fairly short aspect ratio of diameter to depth, and they are used to cut through relatively thin workpieces. However, longer aspect ratios are available for applications that warrant them. Cutting with a hole saw is analogous to some

machining Machining is a process in which a material (often metal) is cut to a desired final shape and size by a controlled material-removal process. The processes that have this common theme are collectively called subtractive manufacturing, which utilizes ...

operations, called ''trepanning'' in the trade, that swing a cutter analogous to a fly cutter in order to achieve a similar result of annular kerf and intact core.

Construction

The saw consists of a metal cylinder, usually

steel Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistan ...

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

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 to 130 mm, or in the US, ¼ to 6 inches. The only limit on the length of the cylinder, and thus depth of the hole, is the need to remove the bit from the hole to clear dust. A 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 is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin ...

plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adapta ...

, soft

plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...

, and

metal A metal (from ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, e ...

. Diamond hole saws are used to bore holes in

brick A brick is a type of block used to build walls, pavements and other elements in masonry construction. Properly, the term ''brick'' denotes a block composed of dried clay, but is now also used informally to denote other chemically cured cons ...

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

, glass, and

stone In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition, and the way in which it is formed. Rocks ...

Types

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 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. For example, a hole would require a huge twist drill or spade drill, unable to be properly driven by a pistol-grip drill or benchtop drill press; but it can be cut with a hole saw with relative ease. Some disadvantages include: * The portable drill used must be capable of producing considerable

torque In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...

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. * The core plug often binds inside the hole saw, and often must be pried out after each hole is cut. Sometimes the prying is quite difficult. * Sometimes the core plug will twist apart mid-cut, creating a condition where the core inside the hole saw spins on the yet-uncut portion of the core still in the workpiece. This tends to stop the cutting action of the saw, and if the workpiece is wood or plastic, the friction will start to singe it, creating a burning smell and heating up the hole saw. The twisted-off core must then be pried out of the hole saw before the cutting can continue.

Diamond 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 (RC), also called reinforced cement concrete (RCC) and ferroconcrete, is a composite material in which concrete's relatively low ultimate tensile strength, tensile strength and ductility are compensated for by the inclusion ...

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 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. Diamond hole saws will drill through tile, porcelain tiles,

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies un ...

marble Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is typically not foliated (layered), although there are exceptions. In geology, the term ''marble'' refers to metamorphose ...

metals A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typical ...

and any lapidary material.

References

{{Reflist Hole making Metalworking cutting tools Saws