ISO 273 · VDI 2230
Fasteners
M3–M24: clearance holes, wrench sizes and tightening torque 8.8 / 10.9 / 12.9.
Loading calculation model…
Questions
Which clearance hole is standard?+
Medium (ISO 273 medium). Fine for accurate alignment, coarse for sheet or rough holes.
Tightening torque M8 8.8?+
27.3 N·m at μ = 0.14, dry, 90 % Rp0.2 (VDI 2230-1 A1). Preload 18 100 N. Lubricated μ is lower — torque down.
Hex or socket?+
SW and k are ISO 4014/4017 (hex). s and dk are ISO 4762 (socket head). Same M thread, different head.
Is this a VDI joint?+
No. Table A1 is a starting value for static, concentric load. Alternating load, clamp ratio and grip length you calculate in VDI 2230.