The weakest points in a bolt is the stressed area in the thread root. The stressed area depends on the type of threads - coarse threads reduces the stressed area compared to fine threads.
UN and UNR Bolts Tensile Stress Area
The stressed area in a bolt can be calculated as
A = (π / 4) (dn - 0.9743/ n)2 (1)
A = stressed area (in2)
dn = nominal bolt diameter (in)
n = 1 / p = number of threads per inch
p = pitch, length per thread (in)
Despite that a reduced area will reduce the breaking load of a bolt - coarse threads are used for clamping. Fine threads bolts are weaker due to the reduced thread height.
ISO 898 Bolts Tensile Stress Area
Tensile stress area in bolts according ISO 898-1 Mechanical properties of fasteners made of carbon steel and alloy steel:
As,nom = (π / 4) ((d2 + d3)/ 2)2 (2)
As,nom = nominal stress area (m, mm2)
d2 = the basic pitch diameter of the external thread according ISO 724 ISO general-purpose metric screw threads -- Basic dimensions (m, mm)
d3 = d1 - H / 6 = the minor diameter of external tread (m, mm)
d1 = the basic minor diameter of external thread according ISO 724
H = the height of the fundamental triangle of the thread according ISO 68-1 ISO general purpose screw threads (m, mm)
Bolts, nuts and threaded rods - torque, tension and loads.
Engineering related topics like Beaufort Wind Scale, CE-marking, drawing standards and more.
Tensile stress and Hooke's Law.
Calculate required bolt torque.
Dimensions of metric threads according ISO 724.
ANSI/SO, DIN and JIS bolts.
Minimum ultimate tensile and proof loads for metric bolts with coarse or fine threads.
Recommended thightening torque metric bolts.
Metric steel bolts, screws and studs - proof and tensile strength.
Lubrication effect on bolt tension and torque.
ASTM steel bolts - proof and tensile strength.
SAE steel bolts - grades ranging grade 1 to 8.2 - proof and tensile strength.
Endurance limits and fatigue stress for steels.
Stress is force applied on cross-sectional area.
Stress is force per unit area - strain is the deformation of a solid due to stress.
Physical properties of thermoplastics like ABS, PVC, CPVC, PE, PEX, PB and PVDF.
ANSI/ASME B1.1 Unified National Thread - UNC Coarse series and UNF Fine series.
Tensile strength and proof loads SAE bolts.
Convert between US Inches and metric mm wrench and spanner sizes.
Young's Modulus (or Tensile Modulus alt. Modulus of Elasticity) and Ultimate Tensile Strength and Yield Strength for materials like steel, glass, wood and many more.