BIZOMAT MAKEOS · Fasteners
Clevis Pin Joint Design (Pin Bending, Shear, Bearing and Eye)
Is this clevis (fork-and-eye) pin joint strong enough: pin bending and shear, bearing in the eye and fork, and tear-out of the eye?
Check of a pinned clevis joint with a central eye between two fork plates: pin bending moment with the load spread over the eye and fork plates and the gaps between them, pin bending stress, double-shear stress (as the bolt and pin shear tool), bearing stress in the eye and in the fork plates, and the eye’s net-section tension and shear tear-out beyond the hole.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Load | kN | Load through the joint. |
| Pin diameter | mm | Diameter of the pin (taken equal to the hole). |
| Eye thickness | mm | Thickness of the eye (the central member). |
| Thickness of each fork plate | mm | Thickness of each of the two fork plates. |
| Gap between eye and each fork plate | mm | Clearance between the eye and each fork plate. |
| Eye edge distance (hole centre to edge) | mm | Distance from the hole centre to the edge of the eye in the load direction. |
| Allowable pin bending stress | MPa | Allowable bending stress of the pin (your value). |
| Allowable pin shear stress | MPa | Allowable shear stress of the pin. |
| Allowable bearing stress | MPa | Allowable bearing stress between pin and plates. |
| Allowable eye tensile stress | MPa | Allowable tensile stress of the eye. |
| Allowable eye shear stress | MPa | Allowable shear stress of the eye. |
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: Load
- What it is
- The total load passing through the joint from the eye to the fork, which puts the pin in double shear.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Every stress rises in direct proportion.
- Get it right
- Enter the whole load in kN, not the share on each fork plate.
What this means: Pin diameter
- What it is
- The diameter of the pin, taken as equal to the hole in the eye and fork plates.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Pin bending stress falls with the cube of diameter, and shear with its square.
- Get it right
- Use the pin diameter in the plates; a reduced or grooved section needs its own check.
What this means: Eye thickness
- What it is
- The thickness of the central eye (the single member between the fork plates), measured along the pin.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A thicker eye lowers its bearing and tension stresses but increases the pin bending moment.
- Get it right
- Measure along the pin axis, not across the eye.
What this means: Thickness of each fork plate
- What it is
- The thickness of each of the two fork plates either side of the eye, measured along the pin.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 1000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Thicker plates lower fork bearing stress but increase the pin bending moment.
- Get it right
- Enter one plate, not both together.
What this means: Gap between eye and each fork plate
- What it is
- The clearance between the eye and each fork plate, measured along the pin.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger gap increases the pin bending moment.
- Get it right
- Enter the gap on one side only.
What this means: Eye edge distance (hole centre to edge)
- What it is
- The distance from the hole centre to the outer edge of the eye in the direction of the load. It sets the eye net tension and tear-out areas.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 2000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 25 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A larger edge distance lowers the eye tension and tear-out stresses.
- Get it right
- Measure in the line of the load; it must exceed the pin radius.
What this means: Allowable pin bending stress
- What it is
- The bending stress you allow in the pin, your design value for the pin material and its treatment.
- 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 250 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Base it on the pin steel and hardness; a reversing load needs a fatigue value.
What this means: Allowable pin shear stress
- What it is
- The shear stress you allow in the pin across its two shear planes.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 2000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 120 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the shear allowable, not the tensile one, for the pin material.
What this means: Allowable bearing stress
- What it is
- The bearing stress you allow between the pin and the plates. The same value is applied to the eye and the fork plates.
- 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 200 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the value for the weaker of the pin and plate materials.
What this means: Allowable eye tensile stress
- What it is
- The tensile stress you allow on the net section of the eye either side of the hole.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 2000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 150 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the allowable for the eye material and your safety rules.
What this means: Allowable eye shear stress
- What it is
- The shear stress you allow in the eye for tear-out of the material between the hole and the edge.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 2000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 100 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use the shear allowable for the eye material.
Method and formulas
- Pin bending with the load spread over the eye and fork plates: M = F (a + 2b + 4g) ÷ 8; σ = 32M ÷ (π d³).
- Double shear τ = F ÷ (2 × π d² ÷ 4) (as the bolt and pin shear tool).
- Bearing: eye F ÷ (d a); fork F ÷ (2 d b).
- Eye net tension F ÷ [(2R − d) a]; tear-out F ÷ [2a (R − d ÷ 2)].
- Example: 20 kN bends the 20 mm pin to 140.06 MPa; shear is 31.831 MPa and the eye bears at 50 MPa.
Limitations
- Uniformly spread bearing loads; a tight fit or rigid plates lowers the pin moment.
- Static loads; reversing loads need fatigue checks and a hardened pin.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a clevis pin for a cylinder or linkage
- Find why clevis pins bend in service
- Check an eye end for a higher load
Who it is for
- Design engineers
- Hydraulic engineers
- Maintenance engineers
What you get
- Pin bending moment and stress
- Pin shear and bearing stresses
- Eye net tension and tear-out
Interpreting the result
- Pin bending often governs: closing the gaps and keeping the fork plates thin relative to the pin helps most.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1535, 1720–1735. Topic reference; no source tables or recommended settings are reproduced.
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Open the Clevis Pin Joint Design (Pin Bending, Shear, Bearing and Eye) calculator