Sunk Key Strength
Check shear stress τ and crushing stress σc of a sunk key (T in N·mm, d/l/h in mm).
Inputs
Formula
Fundamentals
Check shear stress τ and crushing stress σc of a sunk key (T in N·mm, d/l/h in mm).
This tool computes Sunk Key Strength from the formula: τ = 2T/(d·l·h); σc = 4T/(d·l·h)
History
Design theory of gears, threads and bearings matured with machine tools and standardisation (AGMA, ISO) since the Industrial Revolution.
Engineering applications
Used for transmission design, joint strength checks and component selection.
Glossary
| Torque T | Input parameter |
| Shaft dia. d | Input parameter |
| Key length l | Input parameter |
| Shear stress τ | Output result |
| Crushing stress σc | Output result |
How to use
- Fill in Torque T, Shaft dia. d, Key length l, Key height h in the Inputs section (watch the unit on each field).
- Click Calculate; the tool evaluates the formula shown above.
- Read Shear stress τ, Crushing stress σc in the results area.
Formula · Worked Example · Knowledge
Formula
核心计算关系：τ = 2T/(d·l·h); σc = 4T/(d·l·h)
输入变量：
- Torque T
T— N·mm - Shaft dia. d
d— mm - Key length l
l— mm - Key height h
h— mm
输出结果：
- Shear stress τ
tau— MPa - Crushing stress σc
sigc— MPa
假设/适用：Gearing/thread formulas assume standard, zero-backlash mounting; include error & load factors K_A.
Worked Example
根据公式 τ = 2T/(d·l·h); σc = 4T/(d·l·h)，取 Torque T = 50,000 N·mm；Shaft dia. d = 30 mm；Key length l = 40 mm；Key height h = 8 mm。
代入计算得：Shear stress τ = 10.42 MPa；Crushing stress σc = 20.83 MPa。
Key Points
- Gearing/thread formulas assume standard, zero-backlash mounting; include error & load factors K_A.
- Compare stress with allowable stress and keep a safety factor (≥1.5, ≥2 for critical parts).
- For high speed/load also check lubrication, heat and fatigue life, not just static strength.
Parameters
Inputs
| Parameter | Symbol | Unit | Default |
|---|---|---|---|
| Torque T (N·mm) | T | N·mm | 50000 |
| Shaft dia. d (mm) | d | mm | 30 |
| Key length l (mm) | l | mm | 40 |
| Key height h (mm) | h | mm | 8 |
Outputs
| Result | Symbol | Unit |
|---|---|---|
| Shear stress τ | tau | MPa |
| Crushing stress σc | sigc | MPa |
Applications
- Common engineering use cases