Rigid Flange Coupling Torque Capacity
The torque a rigid flange coupling transmits through its bolt circle.
Example
You enter
- Number of bolts n 6
- Bolt diameter d (in) 0.5
- Allowable bolt shear stress (psi) 10000
- Bolt-circle diameter BCD (in) 5
You get
- Torque capacity 29452
- Shear per bolt 1963.5
Checked against published worked examples from: MATHalino.
Details, formula, and sources
ScopeThe bolts share the load in single shear at the bolt-circle radius: T = n (pi/4 d^2 tau)(BCD/2). Six 1/2 in fitted bolts on a 5 in bolt circle at 10,000 psi allowable shear carry 29,450 in-lbf (2,454 ft-lbf), each bolt seeing 1,963 lbf; add bolts, grow the circle, or use bigger bolts to raise it. Fitted (body-bound) bolts carry torque directly in shear; clearance bolts rely on clamp friction. Also check the flange bearing, the shaft key, and the hub - the weakest link governs. A design aid; Machinery Handbook / Shigley and the coupling maker govern.
Formula or tableAb = pi/4 d^2; per-bolt shear = Ab tau; R = BCD/2; T = n (Ab tau) R.
Source and editionThe rigid flange-coupling torque capacity, bolts in single shear at the bolt-circle radius (Machinery's Handbook; Shigley, Mechanical Engineering Design), by name.
Free accessThe flange-coupling torque relation is a standard published machine-design result; the bolt count, diameter, allowable shear, and bolt-circle diameter are the user's inputs.
What governsEstimate. AHJ and licensed professional govern.
API field namesbolt_count, bolt_diameter_in, allowable_shear_psi, bolt_circle_diameter_in, torque_capacity_in_lb, shear_per_bolt_lbf
- Torque capacity T = n (pi/4 d^2 tau)(BCD/2), bolts in single shear sharing equallyMachinery's Handbook / Shigley
- Fitted bolts fitted (body-bound) bolts carry torque in shear; clearance bolts rely on clamp frictioncoupling design
- Scope bolt shear only; flange bearing, key, hub, flexible-coupling misalignment are separatescope of this tile