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Hydraulic Shearing Machines: The Difference Between a Fixed and Variable Rake Angle

June 30, 2015 Equal pressure & equal rake-angle

When purchasing a hydraulic guillotine shearing machine, it is important to consider whether you need a fixed rake angle or a variable rake angle. The rake angle, or the angle of the moving blade when it passes the fixed blade, determines the amount of the material the blade cuts at one time. This has an impact on the quality of the cut, as well as the amount of tonnage needed to complete the job. Let’s take a quick look at the difference between a fixed and variable rake angle.

Why Rake Angle is Important

In addition to having an impact on the overall quality of the cut, the rake angle of the sheared piece of metal determines the amount of twist and bow produced.

Fixed Rake Angle System

When you purchase a hydraulic cutter that has a fixed rake angle, the angle stays set at the manufacturer setting. Hydraulic shearing machine manufacturers calculate the angle to provide superior shear quality for the range of material thicknesses determined by the machine’s tonnage.

Variable Rake Angle System

When you decide to purchase a hydraulic guillotine cutter that operates with a variable rake angle system, the operator has the ability to adjust the angle of the rake to fit certain applications. Hydraulic guillotine shearing machines with a variable rake angle system are usually found in shops with thicker capacity requirements, such as ½ inch or higher. They may choose to use a high rake for cutting parts of metal that are especially thick, while switching to a low rake angle when shearing thinner materials to improve the part quality and to save power.

The Difference between a High and Low Rake Angle

A high rake angle pivots the upper blade down and is able to shear the material using an action similar to scissors. A high rake angle is best used when exact precision is not critical. It is important to watch the cutoff portion to ensure it does not bow, camber, or twist.

When using a low rake angle, the upper blade moves down almost parallel to the lower blade in a guillotine manner. The shearing force expands across the length of the material being cut instead of staying concentrated in a small region. This results in less twisting, bending, and distortions in the cutoff piece. Machines equipped with a lower rake angle require more power than shearing machines with a higher rake.

If you are in need of a high quality hydraulic shearing machine, Preci-Shear is just the place to start and end your search. We base all of our designs on proven traditional designs, as well as the most advanced shearing machine technology. As a result, our shearing machines consistently outperform the competition.

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