BIZOMAT MAKEOS · Fasteners
Pivot Pin and Retaining Ring Check (Clevis Stresses and Axial Retention)
Is this clevis pivot pin strong enough for the load, and will the retaining ring that holds it in take the axial push without failing?
Check of a pivot pin in a clevis held in by a retaining ring: pin bending and shear, bearing in the eye and fork plates, net tension and tear-out of the eye, each against your allowable (as the clevis pin joint tool), the thrust capacity of the ring in shear and of the groove in yield with your safety factor and the least groove distance from the pin end (as the retaining ring thrust tool), checked against the axial load and the pin projection you have.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Radial load on the pin | kN | Load carried by the pin across the clevis. |
| Axial load on the ring | kN | Axial force pushing the pin against the retaining ring (side thrust, misalignment). |
| Pin diameter | mm | Pin diameter (also the ring’s shaft diameter). |
| Eye thickness | mm | Thickness of the eye (the middle member). |
| Thickness of each fork plate | mm | Thickness of each fork plate. |
| 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 eye hole centre to the eye edge in the load direction. |
| Retaining ring | ||
| Ring type | choice | Kind of retaining ring. |
| Ring thickness | mm | Thickness of the retaining ring. |
| Groove depth | mm | Depth of the ring groove. |
| Groove contact fraction (stamped) | % | Share of the groove circumference a stamped ring bears on. |
| Pin projection beyond the groove | mm | Length of pin from the groove to the pin end. |
| Allowables (your values) | ||
| Allowable pin bending stress | MPa | Allowable bending stress of the pin. |
| Allowable pin shear stress | MPa | Allowable shear stress of the pin. |
| Allowable bearing stress | MPa | Allowable bearing stress of the eye and fork. |
| Allowable eye tensile stress | MPa | Allowable tensile stress of the eye. |
| Allowable eye shear stress | MPa | Allowable shear stress of the eye. |
| Shear strength of the ring material | MPa | Shear strength of the ring material. |
| Yield strength of the pin (groove) material | MPa | Yield strength of the pin material at the groove. |
| Shear strength of the pin (groove) material | MPa | Shear strength of the pin material behind the groove. |
| Ring safety factor | Safety factor on the ring thrust capacity. | |
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: Radial load on the pin
- What it is
- The total load the pin carries across the clevis, at right angles to the pin axis. The pin is in double shear between the eye and the two fork plates.
- 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 clevis stress and utilisation rises in proportion to it.
- Get it right
- Use the total load on the joint, not the load on one shear plane.
What this means: Axial load on the ring
- What it is
- The force along the pin axis that pushes the pin against its retaining ring, from side thrust, misalignment or vibration.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 2 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Even a joint with only radial load needs some allowance here; estimate it from the mechanism.
What this means: Pin diameter
- What it is
- The diameter of the pivot pin. The retaining ring is sized for the same shaft diameter.
- 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
- Bending stress falls with the cube of the diameter; shear stress with its square.
What this means: Eye thickness
- What it is
- The thickness of the eye, the middle member through which the pin passes between the two 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.
What this means: Thickness of each fork plate
- What it is
- The thickness of one fork plate of the clevis. Both plates are taken as the same thickness.
- 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.
- Get it right
- Type one plate’s thickness, not the two plates together.
What this means: Gap between eye and each fork plate
- What it is
- The axial clearance between the eye and each fork plate. A larger gap lengthens the pin span and raises its bending moment.
- 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.
- Get it right
- Type the gap on one side only.
What this means: Eye edge distance (hole centre to edge)
- What it is
- The distance from the centre of the eye hole to the outer edge of the eye, measured in the direction of the load. It sets net tension and tear-out.
- 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.
- Get it right
- Measure in the direction the load pulls the pin, not sideways.
Retaining ring
What this means: Ring type
- What it is
- The kind of retaining ring holding the pin: a spiral-wound ring that bears all round the groove, or a stamped ring that bears on only part of it.
- Units and format
- Choose one of 2 options from the list: Spiral-wound (full contact); Stamped (partial contact).
- Example
- The form opens with “Spiral-wound (full contact)” selected as a worked example. Choose the option that matches your case.
- Get it right
- For a stamped ring the groove contact share is used; for a spiral ring it is ignored.
What this means: Ring thickness
- What it is
- The thickness of the retaining ring material, from the ring maker’s catalogue for the ring size used.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 50 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.2 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Ring shear capacity is proportional to the ring thickness.
What this means: Groove depth
- What it is
- The radial depth of the groove cut in the pin for the ring, from the ring maker’s groove dimensions.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 50 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.5 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Groove yield capacity is proportional to the groove depth.
What this means: Groove contact fraction (stamped)
- What it is
- For a stamped ring, the share of the groove circumference the ring actually bears on. It reduces the groove yield capacity.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 1% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 70% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Used only for a stamped ring; take it from the ring maker’s data.
What this means: Pin projection beyond the groove
- What it is
- The length of pin from the groove to the pin end. The groove must sit far enough from the end that the material behind it does not shear out.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0 mm to 500 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Measure from the groove wall that the ring presses against to the pin end.
Allowables (your values)
What this means: Allowable pin bending stress
- What it is
- The bending stress you allow in the pin, from the pin material and your design standard or safety factor.
- 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.
What this means: Allowable pin shear stress
- What it is
- The shear stress you allow in the pin across its two shear planes, from the pin material and your design standard.
- 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.
What this means: Allowable bearing stress
- What it is
- The bearing (contact) stress you allow between the pin and the holes in the eye and fork plates, from your design standard.
- 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 the plate materials.
What this means: Allowable eye tensile stress
- What it is
- The tensile stress you allow in the eye across the net section beside the hole, from the eye material and your design standard.
- 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.
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, from your design standard.
- 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.
What this means: Shear strength of the ring material
- What it is
- The shear strength of the retaining ring material, from the ring maker’s data. It sets how much thrust the ring can take before it shears.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 5000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1000 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Yield strength of the pin (groove) material
- What it is
- The yield strength of the pin material at the groove, which sets how much thrust the groove wall can take before it yields.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 5000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Use yield strength, not tensile strength, for the pin as heat-treated.
What this means: Shear strength of the pin (groove) material
- What it is
- The shear strength of the pin material behind the groove. It sets how far the groove must be from the pin end.
- Units and format
- Enter a number in MPa: megapascals (1 MPa = 1 N/mm²). The form accepts 0.000001 MPa to 5000 MPa. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 300 MPa as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Ring safety factor
- What it is
- The safety factor applied to the ring and groove thrust capacities and to the least groove distance from the pin end.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 20. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 3 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- A higher factor lowers the allowable thrust and lengthens the groove distance needed.
- Get it right
- Take it from the ring maker or your design rules; it is a divisor on capacity.
Method and formulas
- Pin bending moment = F (a + 2b + 4g) ÷ 8; bending, shear, bearing, net tension and tear-out stresses (as the clevis pin joint tool).
- Ring shear capacity = π D t S_s ÷ K; groove yield capacity = π D d_g S_y ÷ K × contact; allowable = the smaller (as the retaining ring thrust tool).
- Least groove distance from the end = K P ÷ (π D S_c).
- Example: the clevis is at 56.023% of its allowables; the ring holds 4.1888 kN axially against 2 kN.
Limitations
- Static loads; reversing loads need a fatigue check of the pin and ring.
- The groove is assumed outside the fork plates, so it does not weaken the loaded pin section.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a hydraulic cylinder or linkage pivot
- Choose a retaining ring for a pin that sees side thrust
- Set the pin projection beyond the fork
Who it is for
- Design engineers
- Machine designers
- Maintenance engineers
What you get
- Clevis stresses and highest utilisation
- Ring and groove thrust capacity
- Groove distance from the pin end
Interpreting the result
- Side thrust is often underestimated: a misaligned cylinder can push a pin out with a large share of its force.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1535, 1720–1735, 1763–1789. Topic reference; no source tables or recommended settings are reproduced.
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Open the Pivot Pin and Retaining Ring Check (Clevis Stresses and Axial Retention) calculator