Shearing is a metalworking process which cuts stock without the formation of chips or the use of burning or melting. Strictly speaking, if the cutting blades are straight the process is called shearing; if the cutting blades are curved then they are shearing-type operations. The most commonly sheared materials are in the form of sheet metal or plates; however rods can also be sheared. Shearing-type operations include: blanking, piercing, roll slitting, and trimming.

A punch (or moving blade) is used to push the piece of raw material against the die (or fixed blade), which is fixed. Usually the clearance between the two is 5 to 10% of the thickness of the material, but dependent on the material. Clearance is defined as the separation between the blades, measured at the point where the cutting action takes place and perpendicular to the direction of blade movement. It affects the finish of the cut (burr) and the machine's power consumption. This causes the material to experience highly localized shear stresses between the punch and die. The material will then fail when the punch has moved 15 to 60% the thickness of the material, because the shear stresses are greater than the shear strength of the material and the remainder of the material is torn. Two distinct sections can be seen on a sheared work piece, the first part being plastic deformation and the second being fractured. Because of normal in homogeneities in materials and inconsistencies in clearance between the punch and die, the shearing action does not occur in a uniform manner. The fracture will begin at the weakest point and progress to the next weakest point until the entire work piece has been sheared; this is what causes the rough edge. The rough edge can be reduced if the work piece is clamped from the top with a die cushion. Above a certain pressure the fracture zone can be completely eliminated. However, the sheared edge of the work piece will usually experience work hardening and cracking. If the work piece has too much clearance, then it may experience roll-over or heavy burring.


When shearing a sheet, the typical tolerance is +0.1 or -0.1, but it is feasible to get the tolerance to within +0.005 or -0.005. While shearing a bar and angle, the typical tolerance is +0.06 or -0.06, but it is possible to achieve the tolerance of +0.03 or -0.03. Surface finishes typically occur within the 250 to 1000 micro inches range, but can range from 125 to 2000 micro inches. A secondary operation is required if one wants better surfaces than this.


Roll slitting, also known as log slitting, is a shearing process that cuts a large roll of material into narrower rolls. The log slitting terminology refers back to the olden days of saw mills when they would cut logs into smaller sections. They would also use these saw mills to cut iron rods into smaller sections; see slitting mill. The multiple narrower strips of material are known as mults (short for multiple). By today's definition, slitting is a process in which a coil of material is cut down into a number of smaller coils of narrower measure. Potential work pieces are selectively thin (0.001 to 0.215 in.) and can be machined in sheet or roll form. Slitting is considered a practical alternative to other methods due to its high productivity and the versatility of materials it can manage.

For harder materials, such as sheet metal, blades cannot be used. Instead a modified form of shearing is used. Two cylindrical rolls with matching ribs and grooves are used to cut a large roll into multiple narrower rolls. This continuous production process is very economical yet precise; usually more precise than most other cutting processes. However, the occurrence of rough or irregular edges known as burrs are commonplace on slit edges. Also, the geometry of these rolls is determined by specific tolerances in addition to the type of material and work piece thickness. Machinery

The splitter consists of three main parts, an uncoiler, splitter, and recoiler" the material is fed from the uncoiler, through the nip between the two circular cutting wheels (one on top and another underneath) and then re-wound in slit pieces on the recoiler.