Shearing
What parameters matter most when setting up a CNC shear?
The critical controls are back-gauge position, blade gap, sheet thickness, material type, and cutting sequence, because these govern positional accuracy and edge condition. Blade clearance must match the material thickness; back-gauge position determines blank length; cutting sequence affects repeatability.
How accurate is CNC shearing?
Published shop guidance cites sheared dimensional checks in the range of roughly ±0.2 to 0.5 mm in some applications, while precision back-gauge systems can hold positional accuracy around ±0.1 to 0.3 mm. Actual part tolerance depends on machine condition, material, thickness, and setup discipline.
When is shearing preferable to laser cutting?
Shearing is preferred for simple straight blanks where speed and cost per cut dominate. Laser cutting is preferred when the part requires complex geometry or tighter tolerances that the shear cannot deliver. Shearing also suits rectangular blanks and structural plate that will be formed, welded, or machined later.
Shearing is a mechanical cutting process that separates sheet or plate by forcing it between upper and lower blades until the material fractures along a straight line. In CNC sheet-metal work, a hydraulic/CNC shear uses programmed back-gauge positioning and blade motion to produce repeatable straight blanks efficiently. It is typically the first blanking step before bending, punching, or forming because straight cuts are fast, repeatable, and low-cost.
In a CNC cell, shearing is the first blanking step for sheet metal before bending, punching, roll forming, or cabinet fabrication because it is fast, repeatable, and low-cost for straight cuts. The operator loads the sheet, sets the back-gauge in the CNC controller, confirms hold-downs and blade gap, then runs a straight full-width cut. The machine’s control manages back-gauge position and work cycle to improve consistency across repeated parts. On a millwork or cabinetry floor, the same concept appears in panel trimming or rough sizing only when the cut path is straight; for non-straight geometry, shearing is not the correct process because it cannot produce curves, holes, slots, or complex contours. In production terms, shearing is chosen when throughput matters more than ultra-tight contour accuracy, especially for rectangular blanks and structural plate where the cut edge will be formed, welded, or further machined later.
Wrong process selection: Trying to shear profiles, notches, or internal cutouts fails because the process only makes straight-line cuts. The flat pattern goes to the shear instead of laser, punch, or router, causing missing geometry and assembly mismatch.
Poor blade-gap setup: When clearance does not match material thickness, the cut shows burr, edge rollover, twist, or indentation. A clean top edge with rough lower edge later interferes with bending, deburring, or fit-up.
Back-gauge or hold-down error: Sheet movement during the stroke makes blanks out-of-square, tapered, or off target. Warped stock, poor squaring to the fence, or low clamp pressure causes bad blank length that carries into downstream bend and reveal errors.