An alligator shear, historically known as a lever shear and sometimes as a crocodile shear, is a metal-cutting shear with a hinged jaw, powered by a

flywheel A flywheel is a mechanical device that uses the conservation of angular momentum to store rotational energy, a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, a ...

hydraulic cylinder A hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment ( engineering vehicles ...

. Alligator shears are generally set up as stand-alone shears; however, there are types for

excavator Excavators are heavy equipment (construction), heavy construction equipment primarily consisting of a backhoe, boom, dipper (or stick), Bucket (machine part), bucket, and cab on a rotating platform known as the "house". The modern excavator's ...

s. The jaw size can range from long. They are generally used to cut ferrous members, such as

rebar Rebar (short for reinforcement bar or reinforcing bar), known when massed as reinforcing steel or steel reinforcement, is a tension device added to concrete to form ''reinforced concrete'' and reinforced masonry structures to strengthen and aid ...

pipe Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circular ...

angle iron Structural steel is steel used for making construction materials in a variety of shapes. Many structural steel shapes take the form of an elongated beam having a profile of a specific cross section. Structural steel shapes, sizes, chemical comp ...

, or I-beams...

Operation

Older alligator shears were powered by a

. 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 metal stock or

scrap Scrap consists of recyclable materials, usually metals, left over from product manufacturing and consumption, such as parts of vehicles, building supplies, and surplus materials. Unlike waste, scrap can have monetary value, especially recover ...

, generally where accuracy is not an important consideration, and the size or shape of the material makes other cutting or shearing options (such as a

cutting torch Principle of burn cutting Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in the United States) and oxy-fuel cutting are processes that use fuel gases (or liquid fuels such as gasoline or petrol, diesel, bio ...

) impractical. 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 and other parts the shredder will not accept.

Safety

The safety requirements for other powered

metalworking Metalworking is the process of shaping and reshaping metals in order to create useful objects, parts, assemblies, and large scale structures. As a term, it covers a wide and diverse range of processes, skills, and tools for producing objects on e ...

shears are contained in

ANSI The American National Standards Institute (ANSI ) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organiz ...

B11.4, but alligator shears are specifically exempted from that standard. Federal

OSHA The Occupational Safety and Health Administration (OSHA; ) is a regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. The United States Congress established ...

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 __NOTOC__ An interpretive discussion is a discussion in which participants explore and/or resolve interpretations often pertaining to texts of any medium containing significant ambiguity in meaning. Education Interpretive discussions are an e ...

dated June 24, 1981, Federal

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 A press brake is a type of brake, a machine used for bending sheet metal and metal plate. It forms predetermined bends by clamping the workpiece between a matching top tool and bottom die.Parker, Dana T. ''Building Victory: Aircraft Manufacturing ...

, also requires a point of operation guarding when used with standardized stock, but not with large-dimension stock.

References

{{Reflist Metalworking cutting tools