A
hacksaw is a fine-tooth saw with a
bladeA blade is that portion of a tool, weapon, or machine with a cutting edge and/or a pointed tip that is designed to cut and/or puncture, stab, slash, chop, slice, thrust, or scrape animate or inanimate surfaces or materials...
under tension in a frame, used for
cuttingCutting is the separation of a physical object, or a portion of a physical object, into two portions, through the application of an acutely directed force. An implement commonly used for cutting is the knife or in medical cases the scalpel...
materials such as
metalA 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...
or
plasticA 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...
s. Hand-held hacksaws consist of a metal arch with a handle, usually a
pistol gripOn a firearm or other tool, the pistol grip is that portion of the mechanism that is held by the hand and orients the hand in a forward, vertical orientation, similar to the position one would take with a conventional pistol such as the M1911....
, with pins for attaching a narrow disposable blade. A screw or other mechanism is used to put the thin blade under tension. 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. On the push stroke, the arch will flex slightly, decreasing the tension on the blade.
Blades
Blades are available in standardized lengths, usually 10 or 12 inches for a standard hand hacksaw. "Junior" hacksaws are half this size. 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 anywhere 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
setA saw set is a device used in the sharpening of hand saws. Once the teeth have been jointed and filed, the saw set is used to adjust the set of each tooth....
in a "wave" set. As for other saws they are set from side to side to provide a
kerfKerf 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...
or clearance when sawing, but the set changes gradually from tooth to tooth in a smooth curve, rather than alternate teeth set left and right.
Hacksaw blades are normally quite brittle, so care needs to be taken to prevent brittle fracture 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 steelHigh speed steelMost copyeditors today would tend to choose to style the unit adjective high-speed with a hyphen, rendering the full term as high-speed steel, and this styling is not uncommon . However, it is true that in the metalworking industries the styling high speed steel is long-established...
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
viceVise may refer to:* Miami Vise, a defunct AFL team* Vise , a mechanical screw apparatus* Vise , an architectural element* Venus In-Situ Explorer * The Vise, TV show* Visé, BelgiumPeople with the surname Vise:...
. 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 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 weldedElectron beam welding is a fusion welding process in which a beam of high-velocity electrons is applied to the materials being joined. The workpieces melt as the kinetic energy of the electrons is transformed into heat upon impact, and the filler metal, if used, also melts to form part of the weld...
to a softer spine. As the price of these has dropped to be comparable with the older blades, their use is now almost universal.
Variants
A
panel hacksaw eliminates the frame, so that the saw can cut into panels of
sheet metalSheet metal is simply metal formed into thin and flat pieces. It is one of the fundamental forms used in metalworking, and can be cut and bent into a variety of different shapes. Countless everyday objects are constructed of the material...
without the length of cut being restricted by the frame.
Junior hacksaws are the small variant, while larger mechanical hacksaws are used to cut working pieces from bulk metal.
A
power hacksaw (or
electric hacksaw) is a type of hacksaw that is powered either by its own
electric motorAn electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
or connected to a
stationary engineA stationary engine is an engine whose framework does not move. It is normally used not to propel a vehicle but to drive a piece of immobile equipment such as a pump or power tool. They may be powered by steam; or oil-burning or internal combustion engines....
. Most power hacksaws are stationary machines but some portable models do exist. 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.
While stationary electric hacksaws are reasonably uncommon they are still produced but saws powered by a stationary engines have gone out of fashion. The reason for using one is that they provide a cleaner cut than an
angle grinderAn angle grinder, also known as a side or disc grinder, is a handheld power tool used for cutting, grinding and polishing.Angle grinders can be powered by an electric motor, petrol engine or compressed air. The motor drives a geared head at a right-angle on which is mounted an abrasive disc or a...
or other types of
sawA 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...
.
Large, power hacksaws are sometimes used in place of a bandsaw for cutting metal stock to length.