BIZOMAT MAKEOS · Fabrication
Plate Shear Capacity Check (Shearing Force, Largest Thickness, Knife Length)
Can my guillotine or plate shear cut this plate, and what is the thickest plate of this material it can cut?
Check of a plate shear (guillotine) for a cut: the shear strength from the tensile strength, the shearing force for parallel blades or raked (inclined) blades with the penetration at fracture, and the machine force with an allowance for parallel blades (as the shearing force tool), then the largest thickness of the same material the shear can cut at its rated capacity, and the cut length against the knife length.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Blades | choice | Parallel blades cut the whole length at once; raked blades cut progressively with much less force. |
| Material thickness | mm | Thickness of the plate. |
| Cut length | mm | Length of the cut (parallel blades shear it all at once). |
| Tensile strength | MPa | Tensile strength of the plate. |
| Shear strength ÷ tensile strength | Shear strength as a share of tensile strength (about 0.8 for steels). | |
| Blade rake angle | ° | Rake angle of the moving blade. |
| Relative blade penetration at fracture | Share of the thickness the blade penetrates before the plate fractures. | |
| Inclined blade factor n | Factor for the inclined blade formula. | |
| Shear rated capacity | kN | Rated force of the shear. |
| Knife (blade) length | mm | Length of the knives. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Blades
- What it is
- Whether the shear has straight parallel blades that cut the whole length at once, or raked (inclined) blades that cut progressively along the length.
- Units and format
- Choose one of 2 options from the list: Straight parallel blades; Straight inclined (raked) blades.
- Example
- The form opens with “Straight inclined (raked) blades” selected as a worked example. Choose the option that matches your case.
- Get it right
- Rake angle, penetration and the inclined blade factor are used only with inclined blades.
What this means: Material thickness
- What it is
- The thickness of the plate or sheet being cut.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 500 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 6 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Force rises in proportion to thickness with parallel blades and with its square with raked blades.
- Get it right
- Use the actual thickness, including any over-rolling tolerance, not the nominal gauge name.
What this means: Cut length
- What it is
- The length of the cut along the blade. With parallel blades the whole length is sheared at once; it is also checked against the knife length.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1200 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- With parallel blades the force rises in proportion to it.
- Get it right
- With raked blades the force does not depend on this length, but it still must fit the knife.
What this means: Tensile strength
- What it is
- The ultimate tensile strength of the plate material, from which the tool works out its shear strength using the ratio below.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 3000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 450 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Shearing force rises in proportion to it.
- Get it right
- Use the supplier’s certificate or data sheet value, not the yield strength.
What this means: Shear strength ÷ tensile strength
- What it is
- The shear strength of the material divided by its tensile strength, used to convert tensile strength into the stress resisting the cut.
- Units and format
- Enter a plain number with no unit. The form accepts 0.3 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.8 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Shearing force rises in proportion to it.
- Get it right
- Enter a ratio, not a percentage; take it from material data for your alloy.
What this means: Blade rake angle
- What it is
- The angle of the moving blade relative to the fixed blade along the cut length. A raked blade shears only part of the length at a time.
- Units and format
- Enter a number in °: degrees of angle. The form accepts 0.1° to 30°. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2° as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- With inclined blades the force falls as the rake angle increases (force varies with 1 ÷ tan of the angle).
- Get it right
- Take it from the shear maker; it applies only to inclined blades.
What this means: Relative blade penetration at fracture
- What it is
- The fraction of the plate thickness the blade has penetrated when the plate fractures and separates, which depends on the material’s ductility.
- Units and format
- Enter a plain number with no unit. The form accepts 0.05 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.4 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- With inclined blades the force rises in proportion to it.
- Get it right
- Enter it as a fraction of the thickness, not a percentage; take it from shearing data for your material. Used only with inclined blades.
What this means: Inclined blade factor n
- What it is
- An empirical multiplier in the inclined blade shearing formula used by the tool. It applies only when inclined blades are selected.
- Units and format
- Enter a plain number with no unit. The form accepts 0.5 to 1. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.8 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- With inclined blades the force rises in proportion to it.
- Get it right
- Take it from the same shearing data source you use for the penetration value.
What this means: Shear rated capacity
- What it is
- The largest cutting force the shear is rated to deliver, from the maker’s plate or manual.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 1000000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 500 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher capacity lowers the share of capacity used and raises the largest thickness the shear can cut.
- Get it right
- Enter it in kN, not tonnes: multiply tonnes-force by 9.81 to get kN.
What this means: Knife (blade) length
- What it is
- The usable length of the shear blades, the longest cut the machine can make in one stroke.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2500 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the usable cutting length, which can be shorter than the blade length if the side housings get in the way.
Method and formulas
- Parallel blades F = τ b t; inclined F = n τ_ratio σ_u p t² ÷ tan (rake); machine force = 1.3F for parallel blades (as the shearing force tool).
- Largest thickness: force grows with t for parallel blades and with t² for raked blades, so t_max = t × (capacity ÷ force) or t × √(capacity ÷ force).
- Cut length against the knife length.
- Example: 118.76 kN of the 500 kN capacity; the shear can cut up to 12.311 mm of this material.
Limitations
- Sharp blades with correct clearance; dull blades or wrong clearance raise the force considerably.
- Rated capacity as given by the maker, usually for mild steel at its rated thickness.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a guillotine before cutting a stronger plate
- Find the thickest stainless a mild-steel-rated shear can take
- Compare raked and parallel blades
Who it is for
- Fabrication supervisors
- Sheet metal workers
- Manufacturing engineers
What you get
- Shearing and machine force
- Use of the rated capacity
- Largest thickness and cut length
Interpreting the result
- Raked blades cut force roughly in proportion to plate thickness, which is why most plate shears have them.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1336–1339. Topic reference; no source tables or recommended settings are reproduced.
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Open the Plate Shear Capacity Check (Shearing Force, Largest Thickness, Knife Length) calculator