Shearing devices play an important role in the sheet metal manufacturing industry, so naturally, there are a plethora of machines designed to perform the many different shearing functions required to achieve a smooth and accurate finish. This week, we take a look at seven of the most common types of shearing devices used in the sheet metal manufacturing industry, including the metal guillotine.
#1: Alligator shear
So-called because of the hinged jaw used to cut metal, alligator shears are powered by a hydraulic cylinder and are mostly used for cutting long metal stock like l-beams, angle iron, pipe or rebar, or to prepare scrap metal for shredding by lopping off anything the shredder will not accept or non-metal fittings.
The cutting motion is actuated by a piston which extends to slowly close the upper ‘jaw’ down alongside the bed. The key strengths of an alligator shear are its cost-effectiveness, strength and durability, it’s drawbacks are its inaccuracy and rough finish.
#2: Metal guillotine
Guillotines consist of a shear table, work-holding device, a gauging device and upper and lower shears. It can be mechanically, hydraulically, or foot-powered and works by clamping the metal with a ram, then moving a metal blade down across a fixed blade to make a cut. The moving blade can either be straight or set on an angle, to decrease the amount of force required to cut a larger piece of metal.
The key strengths of working with a metal guillotine include its speed and cost-effectiveness, which is ideal for high volume production. However, the biggest drawback of a metal guillotine is its tendency to produce a rough edge. These machines are ideal for process parts where aesthetics are not important, or where the metal will go on to be further worked through welding. Always ensure you are employing correct safety measures when operating a guillotine.
#3: Bench shear
A bench mounted shear that offers more mechanical advantage through a compound mechanism, bench shears are ideal for cutting rough shapes from medium-sized pieces of sheet metal. A dynamic piece of machinery, the bench shear can be used for a number of different purposes including 90-degree angle cuts and T-sections as well as cutting both round and square bars.
The strength of a bench shear depends on its size, with larger machines capable of withstanding the highest stresses, but broadly speaking, the key strengths of this type of shearing mechanism are its efficiency and ability to produce a clean cut that’s free of burrs.
#4: Power shears
Ideal for blanking large pieces of sheet metal, power shears are either electrically or pneumatically powered and operated by hand. They work with an upper blade moving towards a lower fixed blade and exerting tension on the cutting material. They are generally used for cutting straight lines or large radius curves.
The key advantages of power shears are their flexibility in cutting curves, efficiency, accuracy, durability and quality finish.
#5: Throatless shear
Perfect for making straight, intricately curved or irregular cuts, the throatless shear differs from the other models on this list because its design allows for the cutting material to be freely moved around.
Snips are hand tools used to cut sheet metal. There are two different types of snips: tinner snips and compound action snips. Tin snips have long handles and short blades, and are generally used to cut low-carbon tin or mild steel. Straight pattern tin snips are ideal for cutting straight lines or gentle curves, whilst duckbill pattern tin snips are ideal for cutting sharper curves. There are also tin snips known as circle pattern, which cut circles, hawksbill pattern which cut radii on the inside and outside of circles as well as cuts which require sharp turns like when cutting holes in pipes.
The other type of snip is the compound action snip, which is used to cut aluminium, mild steel or stainless steel. This type of snip has a linkage, which increases mechanical advantages. Compound action snips come in three different types:
- Straight-cutting (which cut straight and in a wide curve);
- Left-cutting (which cut straight and in a tight curve to the left); and
- Right-cutting (which cut straight and in a tight curve to the right).
Other variations of the compound action design include:
- Upright snips, which are ideal for use in tight spaces;
- Long cuts snips, which are ideal for making longer straight cuts; and
- Hard snips with head treated blades that can be used to cut through tougher metals.
The key strength of snips is their precision and suitability for a wide range of delicate cutting work. However, because they are hand-operated, working with snips is a labour heavy and time-consuming process.
Although some nibblers work like tin snips, most work off a punch and die formation. Nibblers work via a blade which moves in a line around a fixed die in a series of up and down punching strokes, ‘nibbling’ away at the material to create a cut.
The advantages of nibblers include their robustness and durability, its ability to produce distortion-free cuts, speed, and low force feed.
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