Alligator shear
Encyclopedia
An alligator shear, historically known as a lever shear, is a metal
-cutting shear
with a hinged jaw, powered by a flywheel
or hydraulic cylinder
. Alligator shears are generally set up as stand-alone shears, however there are types for excavator
s. The jaw size can range from 4 inch long. They are generally used to cut steel
members, such as rebar
, pipe
, angle iron or I-beams.
. These shears ran continuously, which posed a safety hazard. Now alligator shears are hydraulically actuated. When actuated, the piston arm extends and slowly closes the upper jaw of the alligator shear, which passes alongside the bed or lower jaw of the shear to perform the cut.
, generally where accuracy is not an important consideration, and the size or shape of the material makes other cutting or shearing options impractical- often the only other cutting option is cutting with a torch
. Alligator shears are often used in conjunction with large metal shredders in the metal recycling industry, to 'clean' or prepare scrap for shredding by removing unwanted fittings or other parts the shredder will not accept.
shears are contained in ANSI
B11.4, but alligator shears are specifically excepted from that standard. Federal OSHA
and various state OSHA programs have requirements for guarding alligator shears, and newly-manufactured alligator shears are provided with guards that adjust to the size of the stock or scrap being cut. The purpose of this guard, however, is to prevent pieces of metal from being ejected during cutting. Such a guard also prevents inadvertent exposure of the operator's hands, but does not conform to more stringent 'point of operation' guarding requirements.
In an interpretive letter dated June 24, 1981, Federal OSHA
discussed the guarding dilemma presented by the alligator shear.
These practical considerations for guarding are not exclusive to alligator shears. A much more common type of equipment, the press brake
, also requires point of operation guarding when used with standardized stock, but not with large-dimension stock.
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...
-cutting shear
Shearing (metalworking)
Shearing, also known as die cutting, is a process which cuts stock without the formation of chips or the use of burning or melting. Strictly speaking, if the cutting blades are straight the process is called shearing; if the cutting blades are curved then they are shearing-type operations...
with a hinged jaw, powered by a flywheel
Flywheel
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia, and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed...
or hydraulic cylinder
Hydraulic cylinder
A Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...
. Alligator shears are generally set up as stand-alone shears, however there are types for excavator
Excavator
Excavators are heavy construction equipment consisting of a boom, stick, bucket and cab on a rotating platform . The house sits atop an undercarriage with tracks or wheels. A cable-operated excavator uses winches and steel ropes to accomplish the movements. They are a natural progression from the...
s. The jaw size can range from 4 inch long. They are generally used to cut 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...
members, such as rebar
Rebar
A rebar , also known as reinforcing steel, reinforcement steel, rerod, or a deformed bar, is a common steel bar, and is commonly used as a tensioning device in reinforced concrete and reinforced masonry structures holding the concrete in compression...
, pipe
Pipe (material)
A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases , slurries, powders, masses of small solids...
, angle iron or I-beams.
Operation
Older alligator shears were powered by a flywheelFlywheel
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia, and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed...
. These shears ran continuously, which posed a safety hazard. Now alligator shears are hydraulically actuated. When actuated, the piston arm extends and slowly closes the upper jaw of the alligator shear, which passes alongside the bed or lower jaw of the shear to perform the cut.
Uses
Alligator shears are used for cutting long-length metal stock or scrapScrap
Scrap is a term used to describe recyclable and other materials left over from every manner of product consumption, such as parts of vehicles, building supplies, and surplus materials. Unlike waste, scrap has significant monetary value...
, generally where accuracy is not an important consideration, and the size or shape of the material makes other cutting or shearing options impractical- often the only other cutting option is cutting with a torch
Torch
A torch is a fire source, usually a rod-shaped piece of wood with a rag soaked in pitch and/or some other flammable material wrapped around one end. Torches were often supported in sconces by brackets high up on walls, to throw light over corridors in stone structures such as castles or crypts...
. Alligator shears are often used in conjunction with large metal shredders in the metal recycling industry, to 'clean' or prepare scrap for shredding by removing unwanted fittings or other parts the shredder will not accept.
Safety
The safety requirements for other powered metalworkingMetalworking
Metalworking is the process of working with metals to create individual parts, assemblies, or large scale structures. The term covers a wide range of work from large ships and bridges to precise engine parts and delicate jewelry. It therefore includes a correspondingly wide range of skills,...
shears are contained in ANSI
Ansi
Ansi is a village in Kaarma Parish, Saare County, on the island of Saaremaa, Estonia....
B11.4, but alligator shears are specifically excepted from that standard. Federal OSHA
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...
and various state OSHA programs have requirements for guarding alligator shears, and newly-manufactured alligator shears are provided with guards that adjust to the size of the stock or scrap being cut. The purpose of this guard, however, is to prevent pieces of metal from being ejected during cutting. Such a guard also prevents inadvertent exposure of the operator's hands, but does not conform to more stringent 'point of operation' guarding requirements.
In an interpretive letter dated June 24, 1981, Federal OSHA
Occupational Safety and Health Administration
The United States Occupational Safety and Health Administration is an agency of the United States Department of Labor. It was created by Congress of the United States under the Occupational Safety and Health Act, signed by President Richard M. Nixon, on December 29, 1970...
discussed the guarding dilemma presented by the alligator shear.
In instances where the shear is exclusively used for routine cuts on standardized stock, safeguarding of the point of operation is definable. In other instances, the operator is safeguarded from exposure to the point of operation by the physical size and configuration of the material being cut.
These practical considerations for guarding are not exclusive to alligator shears. A much more common type of equipment, the press brake
Box and pan brake
A brake is a metalworking machine that allows the bending of sheet metal. A cornice brake only allows for simple bends and creases, while a box-and-pan brake also allows one to form box and pan shapes...
, also requires point of operation guarding when used with standardized stock, but not with large-dimension stock.