Shear (sheet metal) and types

Types

Alligator shears historically known as lever shears and sometimes alligator shears, are metal cutting shears with hinged jaws powered by a flywheel or hydraulic cylinder.Alligator shears are usually set up as stand-alone shears; however, there are types for excavators. Jaw sizes range from 4 to 36 inches (100 to 910mm) long.They are typically used to cut ferrous structures such as rebar, pipe, angle iron or I-beams.

Bench scissors

Bench shears, also known as lever shears, are bench shears with compound mechanisms for added mechanical advantage.It is typically used for cutting rough shapes out of medium sized sheet metal parts, but not fine work.For small shears, it is mainly designed for a wide range of applications.Lightweight, easy and efficient to operate, yet extremely robust in construction.The installed cutting blades are carefully and accurately ground for easy, clean, fast cuts and no burrs.These special features help operators save significant energy.But some shears can cut plates and flat bars up to 10mm.It is electrically welded together making it a solid and stable unit capable of withstanding the highest stresses that come with heavy duty use.The treads are reinforced with support angles to give the shears solid stability.The machine is equipped with a section knife with a sliding blade that is manually adjustable to make 90 cuts on angle and T sections of different sizes and has openings for cutting round and square bars

Guillotine

The machines used are called square shears, power shears or guillotines.The machine can be pedal powered, less commonly hand powered, or mechanical or hydraulic powered.It works by first clamping the material with a ram. The blade is then moved down past the stationary blade to cut the material.On larger shears, the moving blade can be set at an angle or "rock" to gradually cut the material from side to side; this angle is called the shear angle.Setting the blade at an angle reduces the force required but increases the stroke.A shear angle of 5 degrees reduces the force by about 20%.The energy used is still the same.The moving blades can also be inclined by 0.5 to 2.5°,called the rake angle, to prevent material from wedging between the blades.However, beveling the blade compromises the squareness of the edge.The machine consists of a shearing table, a workpiece clamping device, upper and lower blades, and a gauge device.The shear table is the part of the machine that the workpiece rests on while it is being cut.Workholding devices are used to hold a workpiece in place and prevent it from moving or bending under force.The upper and lower blades are the mechanical parts that actually make the cut, while the measuring device is used to nsure that the workpiece is machined where it should be.Stamping tool design is an engineering compromise.A sharp edge, strength, and durability are ideal, but a sharp edge is not very strong or durable, so blades used for metal work tend to be squared rather than edged.Typical workpiece materials include aluminum, brass, bronze and mild steel due to their excellent shear ratings.Because stainless steel is prone to work hardening,it is not often sheared.

Other geometric possibilities include square snips, corner snips, bowtie snips, and stick snips.All of these have many different uses, and all are frequently used in certain areas of manufacturing.

Power shears

Electric shears are electric or pneumatically powered liderwally hand tools designed for cutting large sheets of metal.They are designed for cutting straight lines and relatively large radius curves.They are superior to band saws because there is no size limitation.The large version can cut sheet metal up to 12 gauge.An alternative to hand tools are hydraulic power tools attached to heavy machinery.They are typically used to cut material that is too bulky to transport to a cutting facility, that is too large or dangerous for hand tools, and that is stored in remote locations (e.g.mines, forests).