An alligator 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, in which each stroke is actuated by the operator, often with a foot control. They are generally used to cut pipe or other long-length scrap metal material, like angle irons or I-beams.
While there are still mechanical alligator shears in use, powered by flywheels like a mechanical power-operated press, all modern alligator shears are powered by heavy hydraulic pistons. 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.
Alligator shears are used for cutting long-length metal stock or scrap
, 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 torch cutting
. 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.
The safety requirements for other powered metalworking
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.
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, also requires point of operation guarding when used with standardized stock, but not with large-dimension stock.