These values should only be used when the machine manufacturer has not provided their own. Fine pitch bolts also have different torque levels generally specified in the manufacturer’s documentation.

We hope these metric bolt torque charts have helped you discover the correct tightening torque for the bolts you use. They have a proof load of 830 MPa, minimum yield strength of 940 MPa, and a minimum tensile strength of 1040 MPa. Class 10.9 bolts come in sizes ranging from 5 mm to 100 mm. They are often used to secure engines and drives, alongside a host of other demanding applications.

Refer to the charts below, which show the ideal tightening torque for each bolt grade for a variety of sizes. The Engineering ToolBox (2018). Metric Bolts - Minimum Ultimate Tensile and Proof Loads. [online] Available at: https://www.engineeringtoolbox.com/metric-bolts-minimum-ultimate-tensile-proof-loads-d_2026.html [Accessed Day Month Year]. Depending on size, they have a proof load of 580-600 MPa, minimum yield strength of 640-660 MPa, and a minimum tensile strength of 800-830 MPa. Class 8.8 bolts come in all sizes ranging up to 72 mm.

For full table with more Property Classes - rotate the screen! Metric Bolts - Fine Threads -Proof Loads Thread These metric bolt torque charts show the ideal tightening torque for class 8.8, 10.9, and 12.9 bolts for both wet and dry tightening. The bolt’s class indicates its material strength, with higher numbers meaning higher tensile and yield strength. The classes are set by the International Standards Organisation or ISO. The metric classes adhere to ISO standards, set by the International Standards Organisation, that apply across most industrialized nations. Property classes (grades) are defined by ISO 898 (Mechanical properties of fasteners made of carbon steel and alloy steel). This table shows values for threads that have been lightly oiled and the tension is 85% of the proof load. Size (mm)Proof load is defined as the maximum tensile force that can be applied to a bolt that will not result in plastic deformation. A material must remain in its elastic region when loaded up to its proof load typically between 85-95% of the yield strength. Acceptable clamp load is typically 75% of proof load.

Identify the class by the embossed number on the head, then find the size of your bolt in the chart. The ideal tightening torque can be found listed in two columns to the right. The higher the class, the stronger the bolt. The most common metric bolt classes are Class 8.8, Class 10.9, and Class 12.9. Lower and higher classes exist, but do not see as much use. The “wet” column indicates lubricated bolts, whereas the “dry” column indicated unlubricated bolts. Metric Class 8.8 Bolt Torque ChartThey have a proof load of 970 MPa, minimum yield strength of 1100 MPa, and a minimum tensile strength of 1220 MPa. Class 12.9 bolts come in sizes ranging from 1.6 mm to 100 mm. For full table with more Property Classes - rotate the screen! Metric Bolts - Coarse Threads - Proof Loads Thread Compare the bolts you have with the diagrams below, then refer to the appropriate chart to see the ideal tightening torque. Metric Bolt Torque Chart They are made of quenched and tempered medium carbon steel and can be plated with a variety of materials, most commonly zinc.