Hobson tightening torque chart
Class 12.9 Socket Head Cap Screw Tightening Torque Chart, M3 to M64
Hobson's one-page technical table for class 12.9 socket head cap screws. For each size from M3 to M64 it gives pitch, stress and core area, tensile, proof and shear load, and a recommended tightening torque for plain and zinc plated screws.
What this covers
- Pitch and areas
- Tensile, proof and shear load
- Tightening torque, plain
- Tightening torque, zinc plated
- Notes and k factors
Key things to remember
The essentials from this document in plain words. Check the full document before you rely on a figure.
- Recommended tightening torque, plain (k factor 0.2, burr-free threads with a light oil coating) and zinc plated (k factor 0.14): M6 16.4Nm and 11.5Nm, M12 137.4Nm and 96.2Nm, M20 665.4Nm and 465.8Nm.
- The torques are a guide only, for the first tightening of a single assembly in isolation. They do not account for the many things that change friction, and so tension, on a real job.
- Load columns are given per size, for example M12: tensile 102.8kN, proof 81.8kN, shear 55.8kN.
- Sizes M42 to M64 are extrapolated values.
Who it helps: Fitters and engineers setting torque for 12.9 cap screws.
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This document is published by Hobson Engineering, who supply this range to us. We show it here in full so you can read it next to the product; the summary above is ours. Read it on this page or download the PDF. For the most current version, ask us.