Torque and preload for customized geometry and material

Calculate tightening torque, preload and surface pressure for hex head, socket head and countersunk screws. Customized head shapes, hole chamfers, reduced shanks and materials are available options.

Based on VDI 2230:2014

Fastener where torque will be applied

Screw

Nut

Conical
Head diameter of countersunk screw Ød	mm

Inside diameter of plane bearing area da	mm
Outside diameter of plane bearing area dw	mm

Clearance hole - ISO 273

Fine Medium Coarse

Hole chamfer
Chamfer diameter dha	mm

Reduced shank

Reduced shank
Reduced shank diameter dT	mm

Mechanical properties of material, thread size and friction

Property class of screw
Customized material
Minimum yield strength of screw Rp02	N/mm²
Utilization of yield strength %
Thread size
Thread friction value
Nut/bolt head friction value

Data used in calculation

Thread pitch P	mm
Pitch diameter d2	mm
Root diameter d3	mm
Clearance hole dh	mm
Stress area As	mm²

Results

Maximum allowable tightening torque MA	Nm
Maximum possible preload FM	kN
Maximum surface pressure under screw head/nut	N/mm²

Warning:

Many countersunk fasteners are designed with "weak heads". This means that the loadability is reduced and that the theoretical calculated tightening torque cannot be applied!

Guidance for correct tightening torque for such fasteners is found in Bossard's technical catalogue section.

Cross section of reduced shank is larger than stress area in threaded section!

Outside diameter of plane bearing area cannot be smaller than clearance hole!

"Outside diameter of plane bearing area cannot be equal to or smaller than inside diameter of plane bearing area!

Chamfer diameter cannot be equal to or larger than outside diameter of bearing area!

Chamfer diameter cannot be equal to or less than diameter of clearance hole!

Verify your calculation, maximize potential of your product.

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