There are many types of shears used to
shear
Shear may refer to:
Textile production
*Animal shearing, the collection of wool from various species
**Sheep shearing
*The removal of nap during wool cloth production
Science and technology Engineering
*Shear strength (soil), the shear strength ...
or cut
sheet metal
Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Sheet metal is one of the fundamental forms used in metalworking, and it can be cut and bent into a variety of shapes.
Thicknesses can vary significantly; ex ...
.
Types
Alligator shear
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 or hydraulic cylinder. Alligator shears are generally set up as stand-alone shears; however, there are types for excavators. The jaw size can range from 4 to 36 in (100 to 910 mm) long. They are generally used to cut ferrous members, such as rebar, pipe, angle iron, or I-beams.
Bench shear
![LeverShears](https://upload.wikimedia.org/wikipedia/commons/7/79/LeverShears.jpg)
A ''bench shear'', also known as a ''lever shear'', is a
bench mounted shear with a compound mechanism to increase the mechanical advantage. It is usually used for cutting rough shapes out of medium-sized pieces of sheet metal, but cannot do delicate work.
For the small shear, it mostly designed for a wide field of applications. Light weight and easy efficient operation, yet very sturdy in construction. The cutting blades fitted are carefully and accurately ground to give easy, clean quick cuts, and free of burrs. These special features help the operators save a great deal of their energy. But some shearing machines can cut sheet bar and flat bar up to 10mm. It is electrically welded together to make it a sturdy stable unit capable to withstand highest stresses due to heavy duty usage. The footplates are reinforced with bracing angles so that they give firm stability to the shear. The machine is provided with section knives with sliding blades which can be adjusted by hand to make 90 cuts on angles and T-sections of different sizes as well as with openings for cutting round and square bars.
Guillotine
![Gasparini sheet metal hydraulic guillotine power shear](https://upload.wikimedia.org/wikipedia/commons/2/2f/Gasparini_sheet_metal_hydraulic_guillotine_power_shear.jpg)
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
Rake angle is a parameter used in various cutting and machining processes, describing the angle of the cutting face relative to the work. There are three types of rake angles: ''positive'', ''zero'' or ''neutral'', and ''negative''.
* Positive ...
, 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 whilst being shorn. 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 gets worked where it is supposed to be.
The design of
press
Press may refer to:
Media
* Print media or news media, commonly called "the press"
* Printing press, commonly called "the press"
* Press (newspaper), a list of newspapers
* Press TV, an Iranian television network
People
* Press (surname), a fam ...
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
Metalworking is the process of shaping and reshaping metals 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 every scale ...
tend to be ''square-edged'' rather than ''knife-edged''. Typical workpiece materials include aluminum, brass, bronze, and
mild steel
Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:
* no minimum content is specified or required for chromium, cobalt ...
because of their outstanding shearability ratings.
Stainless steel
Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...
is not sheared as often due to its tendency 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
pneumatic
Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air.
Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A central ...
ally powered
hand tool
A hand tool is any tool that is powered by hand rather than a motor. Categories of hand tools include wrenches, pliers, cutters, files, striking tools, struck or hammered tools, screwdrivers, vises, clamps, snips, hacksaws, drills, and kni ...
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
A bandsaw (also written band saw) is a power saw with a long, sharp blade consisting of a continuous band of toothed metal stretched between two or more wheels to cut material. They are used principally in woodworking, metalworking, and lumb ...
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
Hydraulics (from Greek language, Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is th ...
powered tools attached to
heavy machinery
Heavy equipment or heavy machinery refers to heavy-duty vehicles specially designed to execute construction tasks, most frequently involving earthwork operations or other large construction tasks. ''Heavy equipment'' usually comprises five e ...
. 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 (e.g. mines, forests).
Conveyor belt recycling and demolition shear
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Throatless shear
A throatless shear is a cutting tool
A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates ba ...
used to make complex straight and curved cuts in sheet metal
Sheet metal is metal formed into thin, flat pieces, usually by an industrial process. Sheet metal is one of the fundamental forms used in metalworking, and it can be cut and bent into a variety of shapes.
Thicknesses can vary significantly; ex ...
. The throatless shear takes its name from the fact that the metal can be freely moved around the cutting blade (it does not have a throat down which metal must be fed), allowing great flexibility in shapes that can be cut.
Tin snips
Snips, also known as shears, are hand tools used to cut sheet metal and other tough webs. It is a cutting tool. Workers use various types of snips, either straight or blend one be obtained. The straight or bent being not only for straight cuts but for inside of the curvature or concave curvature too. There are two broad categories: tinner's snips, which are similar to common scissors, and compound-action snips, which use a compound leverage handle system to increase the mechanical advantage.
See also
*Nibbler
A nibbler, or nibblers,Jeffery Zurschmeide Automotive Welding: A Practical Guide 2009 - Page 26 "Nibblers make a ragged cut and also leave thousands of little sheetmetal nibbles all over your shop. ... Power shears are the best tool going for cut ...
*Machine tool builders
A machine is a physical system using power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecules ...
*Snips
Snips, also known as shears, are hand tools used to cut sheet metal and other tough web (manufacturing), webs. It is a cutting tool. Workers use various types of snips, either straight or blend one be obtained. The straight or bent being not only ...
References
Bibliography
*
{{Power tools
Metalworking hand tools
Metalworking cutting tools
Fabrication (metal)