A hacksaw is a fine-toothed

saw A saw is a tool consisting of a tough blade, Wire saw, wire, or Chainsaw, chain with a hard toothed edge used to cut through material. Various terms are used to describe toothed and abrasive saws. Saws began as serrated materials, and when man ...

, originally and mainly made for cutting

metal A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...

. The equivalent saw for cutting wood is usually called a

bow saw BOW as an acronym may refer to: * Bag of waters, amniotic sac The amniotic sac, also called the bag of waters or the membranes, is the sac in which the embryo and later fetus develops in amniotes. It is a thin but tough transparent pair of biol ...

. Most hacksaws are

hand saw In woodworking and carpentry, hand saws, also known as "panel saws", are used to cut pieces of wood into different shapes. This is usually done in order to Woodworking joints, join the pieces together and carve a wooden object. They operate by ...

s with a C-shaped walking frame that holds a

blade A blade is the Sharpness (cutting), sharp, cutting portion of a tool, weapon, or machine, specifically designed to puncture, chop, slice, or scrape surfaces or materials. Blades are typically made from materials that are harder than those they a ...

under tension. Such hacksaws have a handle, usually a

pistol grip On a firearm or other tools, a pistol grip is a distinctly protruded handle underneath the main mechanism, to be held by the user's hand at a more vertical (and thus more ergonomic) angle, similar to how one would hold a conventional pistol. ...

, with pins for attaching a narrow disposable blade. The frames may also be adjustable to accommodate blades of different sizes. A screw or other mechanism is used to put the thin blade under tension. On hacksaws, as with most frame saws, the blade can be mounted with the teeth facing toward or away from the handle, resulting in cutting action on either the push or pull stroke. In normal use, cutting vertically downwards with work held in a bench vise, hacksaw blades are set to be facing forwards.

History

While saws for cutting metal had been in use for many years, significant improvements in longevity and efficiency were made in the 1880s by Max Flower-Nash. George N. Clemson, a founder of Clemson Bros. Inc of Middletown,

New York New York most commonly refers to: * New York (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

, United States, conducted tests which involved changing the dimensions, shapes of teeth, styles of set, and variable heat treatments of blades. Clemson claimed enormous improvements to the cutting ability of blades and built a major industrial operation manufacturing hacksaw blades sold under the trade name Star Hack Saw. In 1898, Clemson was granted US Patent 601947, which details various improvements in the hacksaw.

Design

left, Small hacksaw (also known as junior hacksaw). The teeth of the hacksaw blade point forward, away from the handle Standard hacksaw blade lengths are . Blades can be as small as . Powered hacksaws may use large blades in a range of sizes, or small machines may use the same hand blades. The pitch of the teeth can be from fourteen to thirty-two teeth per inch (TPI) for a hand blade, with as few as three TPI for a large power hacksaw blade. The blade chosen is based on the thickness of the material being cut, with a minimum of three teeth in the material. As hacksaw teeth are so small, they are

set Set, The Set, SET or SETS may refer to: Science, technology, and mathematics Mathematics *Set (mathematics), a collection of elements *Category of sets, the category whose objects and morphisms are sets and total functions, respectively Electro ...

in a "wave" set. As for other saws they are set from side to side to provide a

kerf A saw is a tool consisting of a tough blade, wire, or chain with a hard toothed edge used to cut through material. Various terms are used to describe toothed and abrasive saws. Saws began as serrated materials, and when mankind learned how t ...

or clearance when sawing, but the set of a hacksaw changes gradually from tooth to tooth in a smooth curve, rather than alternate teeth set left and right. Hacksaw blades are normally quite

brittle A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. ...

, so care needs to be taken to prevent

brittle fracture Fracture is the appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity sur ...

of the blade. Early blades were of carbon steel, now termed 'low alloy' blades, and were relatively soft and flexible. They avoided breakage, but also wore out rapidly. Except where cost is a particular concern, this type is now obsolete. 'Low alloy' blades are still the only type available for the Junior hacksaw, which limits the usefulness of this otherwise popular saw. For several decades now, hacksaw blades have used

high speed steel High-speed steel (HSS or HS) is a subset of tool steels, commonly used as cutting tool material. Compared to high-carbon steel tools, high-speed steels can withstand higher temperatures without losing their temper (hardness), allowing use of f ...

for their teeth, giving greatly improved cutting and tooth life. These blades were first available in the 'All-hard' form which cut accurately but were extremely brittle. This limited their practical use to benchwork on a workpiece that was firmly clamped in a

vice A vice is a practice, behaviour, Habit (psychology), habit or item generally considered morally wrong in the associated society. In more minor usage, vice can refer to a fault, a negative character trait, a defect, an infirmity, or a bad or unhe ...

. A softer form of high speed steel blade was also available, which wore well and resisted breakage, but was less stiff and so less accurate for precise sawing. Since the 1980s,

bi-metal Bimetal refers to an object that is composed of two separate metals joined together. Instead of being a mixture of two or more metals, like alloys, bimetallic objects consist of layers of different metals. Trimetal and tetrametal refer to objects c ...

blades have been used to give the advantages of both forms, without risk of breakage. A strip of high speed steel along the tooth edge is electron beam welded to a softer spine. As the price of these has dropped to be comparable with the older blades, their use is now almost universal. The most common blade is the 12 inch or 300 mm length. Hacksaw blades have a hole at each end for mounting them in the saw frame and the 12 inch / 300 mm dimension refers to the center to center distance between these mounting holes.Machinery's Handbook, 14th Edition, by Erik Oberg & F. D. Jones, The Industrial Press, 1952, pages 1390-1391 The kerf produced by the blades is somewhat wider than the blade thickness due to the set of the teeth. It commonly varies between 0.030 and 0.063 inches / 0.75 and 1.6 mm depending on the pitch and set of the teeth.

Uses

Hacksaws were originally and principally made for cutting

, but can also cut various other materials, such as plastic and wood; for example,

plumber A plumber is a tradesperson who specializes in installing and maintaining systems used for potable (drinking) water, hot-water production, sewage and drainage in plumbing systems.

s and

electrician An electrician is a tradesman, tradesperson specializing in electrical wiring of buildings, transmission lines, stationary machines, and related equipment. Electricians may be employed in the installation of new electrical components or the ...

s often cut

plastic pipe Plastic pipe is a tubular section, or hollow cylinder, made of plastic. It is usually, but not necessarily, of circular cross-section, used mainly to convey substances which can flow—liquids and gases (fluids), slurries, powders and masses of sm ...

and plastic conduit with them, while

surgeon In medicine, a surgeon is a medical doctor who performs surgery. Even though there are different traditions in different times and places, a modern surgeon is a licensed physician and received the same medical training as physicians before spec ...

s can use unpowered saws as

bonesaw A bone cutter is a surgical instrument used to cut or remove bones. In addition to surgery, they are also used in forensics and dismemberment. Types of medical bone cutters include: * unpowered saw, Unpowered – Unpowered bone cutting imple ...

Variants

left, A panel hacksaw An electric hacksaw A ''panel hacksaw'' has a frame made of a deep, thin sheet aligned behind the blade's kerf, so that the saw could cut into panels of

sheet metal Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Thicknesses can vary significantly; extremely thin sheets are considered foil (metal), foil or Metal leaf, leaf, and pieces thicker than 6 mm (0.25 ...

without the length of cut being restricted by the frame. The frame follows the blade down the kerf into the panel. ''Junior hacksaws'' are a small version with a half-size blade. Like

coping saw A coping saw is a type of bow saw used to cut intricate external shapes and interior cut-outs in woodworking or carpentry. It is widely used to cut moldings to create coped rather than mitre joints. It is occasionally used to create fretwork ...

s, the blade has pins that are held by notches in the frame. Although potentially a useful tool for a toolbox or in confined spaces, the quality of blades in the Junior size is restricted and they are only made in the simple low alloy steels, not HSS. This restricts their usefulness. A ''power hacksaw'' (or ''electric hacksaw'') is a type of hacksaw that is powered either by its own

electric motor An electric motor is a machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a electromagnetic coil, wire winding to gene ...

or connected to a

stationary engine A stationary engine is an engine whose framework does not move. They are used to drive immobile equipment, such as pumps, generators, mills or factory machinery, or cable cars. The term usually refers to large immobile reciprocating engines, ...

. Most power hacksaws are stationary machines but some portable models do exist; the latter (with frames) have been displaced to some extent by

reciprocating saw A reciprocating saw is a type of handheld, small, machine-powered saw, in which the cutting action is achieved through a push-and-pull ("reciprocating") or back-and-forth motion of the blade. The original trade name, Sawzall, is often used in th ...

s such as the Sawzall, which accept blades with hacksaw teeth. Stationary models usually have a mechanism to lift up the saw blade on the return stroke and some have a coolant pump to prevent the saw blade from overheating. Power hacksaws are not as commonly used in the metalworking industries as they once were.

Bandsaw A bandsaw (also written band saw) is a power saw with a long, sharp blade consisting of a continuous band of toothed metal stretched between two or more wheels to cut material. They are used principally in woodworking, metalworking, and lum ...

s and

cold saw A cold saw is a circular saw designed to cut metal which uses a toothed blade to transfer the heat generated by cutting to the chips created by the saw blade, allowing both the blade and material being cut to remain cool. This is in contrast to ...

s have mostly displaced them. While stationary electric hacksaws are not very common, they are still produced. Power hacksaws of the type powered by stationary engines and

line shaft A line shaft is a power-driven rotating shaft for power transmission that was used extensively from the Industrial Revolution until the early 20th century. Prior to the widespread use of electric motors small enough to be connected directly to ...

s, like other line-shaft-powered machines, are now rare; museums and antique-tool hobbyists still preserve a few of them.

References

{{Machine and metalworking tools Cutting machines Hand tools Saws Metalworking cutting tools Metalworking hand tools

History

Design

Uses

Variants

See also

References