Shearing (manufacturing): Difference between revisions
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'''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.<ref name=degarmo424>Degarmo, p. 424.</ref> 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 (metalworking)|blanking]], [[Piercing (metalworking)|piercing]], and trimming. |
'''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.<ref name=degarmo424>Degarmo, p. 424.</ref> 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 (metalworking)|blanking]], [[Piercing (metalworking)|piercing]], and trimming. |
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===Bibliography=== |
===Bibliography=== |
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*{{Citation | last = Degarmo | first = E. Paul | last2 = Black | first2 = J T. | last3 = Kohser | first3 = Ronald A. | title = Materials and Processes in Manufacturing | publisher = Wiley | year = 2003 | edition = 9th | isbn = 0-471-65653-4}}. |
*{{Citation | last = Degarmo | first = E. Paul | last2 = Black | first2 = J T. | last3 = Kohser | first3 = Ronald A. | title = Materials and Processes in Manufacturing | publisher = Wiley | year = 2003 | edition = 9th | isbn = 0-471-65653-4}}. |
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[[Category:Metalworking]] |
[[Category:Metalworking]] |
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Revision as of 03:03, 18 July 2008
 | It has been suggested that Guillotine (metalwork) be merged into this article. (Discuss) Proposed since July 2008. |
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.[1] 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, and trimming.
Principle
A punch (or moving blade) is used to push the workpiece 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. This causes the material to experience highly localized shear stresses between the punch and die. The material will then fail when the punch as 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 workpiece, the first part being plastic deformation and the second being fractured. Because of normal inhomogeneities 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 workpiece has been sheared; this is what causes the rough edge. The rough edge can be reduced if the workpiece is clamped from the top with a die cushion. Above a certain pressure the fracture zone can be completely eliminated.[2]
Straight shearing
Straight shearing is done on sheet metal and plates. The machine used is called a squaring shear or power shear. It works by first clamping the material with a ram. A moving blade then comes down across a fixed blade to shear the material. For larger shears the moving blade may be set on an angle or "rocked" in order to shear the material progressively from one side to the other. This decreases the amount of force required, but increases the stroke. The amount of energy used is still the same. The moving blade may also be inclined 0.5 to 2.5° to keep the material from becoming wedged between the blades, however it compromises the squareness of the edge.[3]
References
Notes
Bibliography
- Degarmo, E. Paul; Black, J T.; Kohser, Ronald A. (2003), Materials and Processes in Manufacturing (9th ed.), Wiley, ISBN 0-471-65653-4.
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