What are the different types of shears used in sheet metal?
- Alligator shear
- Bench shear
- Throatless shear
- Metal guillotine
Shearing tools and equipment play a critical role in the metal fabrication and manufacturing industry. Naturally, there will be a variety of these devices that are suited for different types of shearing functions for a smooth, accurate, and tight-tolerance finish. In this guide, we’ll look into some of the most common types of shears used in sheet metal. While most of them are capable of cutting different sheets of metal — be it aluminum, steel, or stainless steel, these devices differ in the method of cutting and appearance. Read on to learn more.
Also referred to as the “crocodile shear” the alligator shear takes its name from the form and appearance of its hinged opening. Like many types of equipment of its stature, the alligator shear is powered hydraulically through a cylinder and is typically used to cut prefinished long metal stocks. Some examples of these would be angle bars, deformed bars, rebars, I-beams, L-beams, castellated beams, and the like.
For the alligator shear, the cutting motion is produced with the help of a piston that extends as the machine is in operation. This leads to the closing of the machine’s “upper jaw” and clamps down the bed.
Alligator shears have been widely used in the industry because of their simple function and cost-effectiveness. However, it’s not really reliable when it comes to producing smooth finishes. Alligator-sheared structural steel, for example, will tend to have inaccuracies and rough finishes in its form.
Bench shears can be powered hydraulically or pneumatically, depending on the features. Most markets will sell small hand shears that can be operated by a single individual, while other companies will also share electric sheet metal shears that have higher power and strength (ideal for cutting thick-walled or stronger metal stocks).
This type of shear has been considered the most mechanically advantageous due to its operational form. Its compound mechanism makes it a dynamic machine, being able to cut through a variety of metal thicknesses and types. It can also produce rough or smooth edges, as configured by the operator.
Larger bench shears can resist increased material stress, but nevertheless, they produce the same efficiency as any small or medium-sized bench shear would. Unlike the alligator shear, metal parts that have been cut through bench shearing sport a smooth and clean look, free from rough edges and burrs.
When you think of shearing equipment, you’ll likely imagine that they can perform only a single type of cut, which is a straight line. This is generally true for most machines, but in order to achieve intricate patterns and shapes for a specific metal specimen, metal fabricators will make use of a throatless shear. This is the most suitable shearing tool in any case where the metal design requires complex curved cuts or precision-drawn straight lines.
Throatless shears, unlike their counterparts, do not present any limitations as to how freely the metal specimen can be moved around the cutting blade. This is because they do not have a “throat” or a component where the metal is usually fed into the machine. As the operator makes use of the throatless shear, they can move the metal across the equipment and make a variety of cuts as they wish — from straight, round, or irregular.
With its long handle, the throatless shear is capable of cutting thin and lightweight metals, like aluminum and mild steel. But throatless shears may not be able to cut through thicker metals. In this case, a sharper hardened steel cutting blade should be used.
Changing gears for a bit, we head to another form of metal shear, known as the snips. These are hand shearing tools that can be classified into two: tinner snips and compound action snips.
Tinner snips or tin snips may look similar to a pair of scissors but they can cut through much more than just paper or cardboard. They’re also far stronger and can be easily controlled, especially when cutting mild steel or low carbon steel. These hand shears come in different blade designs that can perform straight or sharp curve cuts.
On the other hand, compound action snips are used to modify aluminum mild steel or even stainless steel. Each blade in a compound snip is linked together to improve flexibility and mechanical advantages.
A metal guillotine has several key components: an upper & lower blade, hydraulic pistons, compressors, blank holder, and a clamp. The blades can cut, shear, or blank different thicknesses of metals together. Once this has been satisfied, the clamping unit can be used to eject the precision-cut component from the machine.
Guillotine shears can have varying lengths of up to 6 meters and can cut through 30 mm of metal sheets. In order to accommodate curved and asymmetrical designs, the upper blade is also tilted at an angle in order to increase the ease of cutting.
Covered in this short guide are 5 of the most common types of shears used in sheet metal fabrication. The alligator shear, for example, has a unique design that allows it to form rough cuts on different metals. For cleaner looks and smoother finishes, other kinds of shears are also available, such as the throatless shear, on the bench shear.
Although each metal shear has its own advantages and disadvantages, manufacturers understand when and where to use the correct machinery to achieve a specific design. Nevertheless, these shearing devices remain an important tool in the world of manufacturing and have benefitted a number of industries for many decades now.