What is the torque standard for M12 bolts?
2 Answers
M12 refers to the bolt, which corresponds to a 19 nut. Bolt standards: No bolt strength grade is provided. Generally, an 8.8 strength grade bolt requires a tightening torque of 86.9 NM. The tightening torque range for bolts from the lowest grade 3.6 to the highest grade 12.9 is from 24.4 NM to over 147 NM, which is standard for bolts without coating or lubrication. Torque method: It should reach 90% of the screw's yield strength. The friction coefficient is 0.14, and the final tightening should be completed smoothly and slowly with a torque wrench.
When discussing the torque standards for M12 bolts, I must say there's no one-size-fits-all figure—it primarily depends on the bolt's material grade and application scenario. For instance, in automotive repairs, an M12 hub bolt with an 8.8-grade strength typically requires 70-80 Nm of torque, while higher-grade 10.9 bolts may demand 90-110 Nm. Specifications vary across vehicle manuals, so I always emphasize consulting the manufacturer's guidelines. I've witnessed cases where improper tightening by owners led to bolt fractures and catastrophic wheel detachment. Additionally, lubrication significantly impacts torque—applying grease reduces the required torque by about 20% to avoid thread damage from over-tightening. For safety, always use a calibrated torque wrench and regularly inspect tools.
