The machine used is called a squaring shear, power shear, or guillotine. The machine may be foot powered, less commonly hand powered, or mechanically or hydraulically powered. It works by first clamping the material with a ram. A moving blade then comes down across a fixed blade to shear the material. For larger shears the moving blade may be set on an angle or "rocked" in order to shear the material progressively from one side to the other; this angle is referred to as the shear angle. Setting the blade on an angle decreases the amount of force required, but increases the stroke. A 5-degree shear angle decreases the force by about 20%. The amount of energy used is still the same. The moving blade may also be inclined 0.5 to 2.5°, called the rake angle, to keep the material from becoming wedged between the blades. However, raking the blade compromises the squareness of the edge. The machine consists of a shear table, work-holding device, upper and lower blades, and a gauging device. The shear table is the part of the machinery that the workpiece rests on while being sheared. The work-holding device is used to hold the workpiece in place and keep it from moving or buckling while under stress. The upper and lower blades are the piece of machinery that actually do the cutting, while the gauging device is used to ensure that the workpiece is being cut where it is supposed to be. The design of press tools is an engineering compromise. A sharp edge, strength, and durability are ideal, but a sharp edge is not very strong or durable, so blades for metal work tend to be square-edged rather than knife-edged. Typical workpiece materials include aluminum, brass, bronze, and mild steel because of their outstanding shearability ratings. Stainless steel is not sheared as often due to its tendencies to work-harden. Other geometric possibilities include the squaring shear, angle shear, bow-tie shear and bar shear. All of these have many different uses and are all used regularly in certain manufacturing fields.
Power shears
A power shear is electrically or pneumatically powered hand tool designed to blank large pieces of sheet metal. They are designed to cut straight lines and relatively large radius curves. They are advantageous over a bandsaw because there is not a size limit. Large versions can cut sheet metal up to 12 gauge. An alternative to the hand tools are hydraulically powered tools attached to heavy machinery. They are usually used to cut materials that are too bulky to be transported to a cutting facility, too big or dangerous for the hand tools and are stored at remote locations.
Throatless shear
A throatless shear is a cutting tool used to make complex straight and curved cuts in sheet metal. The throatless shear takes its name from the fact that the metal can be freely moved around the cutting blade, allowing great flexibility in shapes that can be cut.
