5 Factors to Consider Before Buying Metal Cutting Shears

Working in metal fabrication uses a lot of machinery, and metal shearing is one of them. In fact, shearing is usually the first step in the process. Adjust your material into manageable and actionable parts. Metal shears have been around in some form for years. 

The type of metal shears you need ultimately depends on what you need to use them for. They are rated on the ability to cut a certain thickness of steel to a certain length. However, they vary in design and are equipped with different options for different levels of production requirements

Metal shearing is a term used in the metal fabrication process. This is a process used to trim unwanted material or trim sheet metal. It cuts a straight line and is used when you need to resize a workpiece or prepare a blank for subsequent metal processing such as CNC stamping. 

The shearing process involves using a machine or tool to cut sheet metal. These tools are designed to cut with extreme precision. Shearing does not require the use of heat and does not generate waste in the form of shavings or stray metal fragments. This makes it a popular choice for manufacturers as it is common to get the most out of the material.

The machine used holds the sheet metal in place with a series of pressurized clamps called "hold downs", and then the blade on the top of the machine moves down through the lower blade to cut. Instead of being placed in the same position, the upper and lower blades are offset slightly to avoid collisions while providing the cleanest cutting edge possible. The slight difference is called blade clearance. 

Usually, the lower blade remains stationary (fixed) while the upper blade is pushed down with a lot of force. The upper blade is fixed at a small angle to the lower blade. This angle allows cutting from one end to the other, rather than all at once. It reduces the force required to cut metal. The blades themselves feature different qualities of tool steel to increase hardness, wear resistance, or shock absorption. 

Metal cutting shears have different capabilities for different materials. They also feature more technological advancements, so they make work faster and more efficient. 

The type, thickness, and consistency of the material you are shearing will greatly affect the recommended choice of the shearing machine you purchase. If you're cutting thin gauge metal or lightweight aluminum, you'll probably use a pneumatic or electric shear, and if you're cutting a 3/4" board with plasma cut holes, you might really need to consider a good mechanical shear to deal with shock absorption capacity.

Consider not only the type of material but also the construction of the material, such as tread panels, expanded metal, perforated metal, etc., which all have different shear forces than flat materials of the same brand.

The number of parts you need to cut is almost as important as the type of material you cut. While basic and inexpensive machines may be suitable for intermittent use in small batches, more complex or robust machines are required for production tasks such as steel service centers. 

Not only are these machines available in a variety of designs, but they can also be equipped with a number of options, including conveyors/stackers that stack sheared material on pallets for quick removal. Other options can include high-speed hydraulics or more precise front-measurement options. 

When you choose a shearing machine, one of the choices you have to make is the drive or the power system behind it. Different drive systems are available to meet different production needs and different cost structures. 

Manual shears - Manually operated shears, sometimes referred to as "stomp" shears, are suitable for the lightest gauge materials in the metalworking market. Common in HVAC and roofing, the stomp shear is a low-volume, light-duty machine primarily used in the 18 Gage. 

Pneumatic - While pneumatics do not greatly increase shearing capacity, pneumatically driven shears do reduce operator fatigue and allow metal shears to be operated at faster speeds.

Electric shears - Electric shears are shears that are simply driven by an electric method, without the advantage of a flywheel to increase inertia, thereby increasing tonnage/force. These shears can machine to 12-14 gauge steel and offer quiet, smooth, and very fast operation. 

Hydraulic shears - Hydraulic is the next preferred method of driving shear blades. Primarily used on 14 Gage shears and thicker hydraulics, they are easy to produce, place, and service, and are significantly less expensive than their mechanically driven counterparts, but they may lack the speed and durability of other systems.

Mechanical shears - If you're looking for shear with the best production ratings, longest duration, and shock absorbing design, it's definitely a mechanical shear. Mechanical shears are simpler, quieter, faster, run cooler, and are designed to run all day, every day. These are the shears of choice for heavy production needs, such as steel service centers.

Once you've decided on the type of drive for your shears, you'll need to know which design style might better suit your needs. There are two basic design types of shears on the market (whether mechanically or hydraulically driven), they are guillotine or pendulum beam. 

The guillotine design of the shearing machine means that the upper blade is directly driven downward by the drive mechanism, and the swing beam rotates the upper blade through leverage, forcing the blade downward.

The guillotine style offers a stronger but more expensive shearing system, while the swing beam style uses a smaller drive (hydraulic) assembly because it takes advantage of leverage in its design. 

The rake angle is the angle at which the upper shear blade is inclined so that it does not touch too much material during the cutting process. The lower the rake angle, the better the quality of the resulting shear edge (including twist, bow, and camber), but the stronger and stronger the shear force must be. A lower rake angle engages more blades in the material, requiring more force (and therefore more machine) to cut. 

Ideally, the rake angle for a perfect cut would be zero, but the force required to cut even the thinnest of materials would be astronomical, making the machine itself prohibitively expensive. Adjustable rake angles allow smaller shears to engage thicker materials, but at a cost. As the rake angle increases, shear edge quality, blade life, and machine stress increase. Thin shear bands may twist or bend due to the large rake angle. 

Hope the above information can help you choose a suitable metal shearing machine, if you need help or want to buy a metal shearing machine, please contact us.

HENGLI is a professional custom sheet metal cutting machines manufacturer. Our main products are: automotive outer panel stamping and forming automation systems, online robots, high-precision sheet metal automatic shearing devices, industrial automation online inspection systems, electrical automation devices, and overall solutions for automation control. The main products are synchronized with the world's advanced technology and are widely used in the pillar industries of the national economy such as automobile manufacturing and parts processing, iron and steel metallurgy processing, electric power, and metal packaging.