--- title: "Tightening Torque Reference" description: "Tightening Torque Reference to Calculated (see note); not specified by ISO 898: sizes M4 to M36. 15 catalogued sizes with materials and finishes." url: https://engineeringhardware.com/fastener/tightening-torque-reference/ source: Engineering Hardware & Fasteners --- # Tightening Torque Reference Engineering Reference · Tightening Torque Reference 15 catalogued sizes, dimensioned to Calculated (see note); not specified by ISO 898. Pick any row and the technical drawing redraws to it. Tightening Torque Reference to Calculated (see note); not specified by ISO 898 are catalogued in sizes M4 to M36. 15 sizes are held in the table below, and the technical drawing redraws to whichever row you select. - **Standard:** Calculated (see note); not specified by ISO 898 - **Size range:** M4-M36 - **Catalogued sizes:** 15 Dimensions are nominal values from the governing standard. Confirm the tolerance class for your application before ordering. ![Tightening Torque Reference technical product image](https://engineeringhardware.com/wp-content/uploads/2026/06/108-All-Metal-Prevailing-Torque-Hex-Lock-Nut-Type-1-—-GB／T-6184-／-ISO-7042-Series-047-—-GB／T-6184-／-ISO-7042.webp) Tightening Torque Reference are engineering reference manufactured to Calculated (see note); not specified by ISO 898. This page lists the full dimensional range with the key specifications engineers need to select and specify them. ## About This Reference This is an engineering reference table for tightening torque reference based on Calculated (see note); not specified by ISO 898. Use it alongside our fastener catalog when selecting and specifying parts. ## Reference Data (Calculated (see note); not specified by ISO 898) | Size | Torque cl.4.6 (Nm) | Torque cl.8.8 (Nm) | Torque cl.10.9 (Nm) | Torque cl.12.9 (Nm) | Description | | --- | --- | --- | --- | --- | --- | | M4 | – | 2.9 | – | 5 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M5 | 2.2 | 5.9 | 8.7 | 10 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M6 | 3.8 | 10 | 15 | 17 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M8 | 9.1 | 24 | 36 | 42 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M10 | 18 | 48 | 71 | 83 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M12 | 32 | 84 | 124 | 145 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M14 | 50 | 134 | 197 | 231 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M16 | 78 | 209 | 306 | 358 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M18 | 108 | 297 | 423 | 495 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M20 | 153 | 420 | 598 | 700 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M22 | 208 | 573 | 816 | 954 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M24 | 264 | 726 | 1034 | 1210 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M27 | 387 | 1064 | 1516 | 1774 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M30 | 525 | 1443 | 2055 | 2405 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | | M36 | 917 | 2523 | 3593 | 4204 | Calculated: preload 65% of proof stress, nut factor K = 0.20 (plain or zinc-plated steel, assembled dry, unlubricated). Lubrication lowers this by roughly a quarter. ISO 898-1 specifies mechanical properties, not tightening torque. An equipment maker's specified torque always governs. | Inside the plant ## Manufactured in our own plant This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided. 1. ![Wire rod feeding into a cold heading machine](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 01 **Cold heading** Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail. Head dimensions and under-head radius checked at set-up and per shift. 2. ![Thread rolling machine producing bolt threads](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 02 **Thread rolling** Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch. Go / no-go ring gauges to ISO 965 tolerance class 6g. 3. ![Baskets of bolts staged for heat treatment](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 03 **Heat treatment** Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it. Core hardness and tensile tested per lot to ISO 898-1. 4. ![Zinc plated bolts in a treatment basket](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 04 **Surface treatment** Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list. Coating thickness and neutral salt spray hours to ISO 9227. ## Frequently Asked Questions ### What does the Tightening Torque Reference reference table cover? Tightening Torque Reference is an engineering reference table aligned with Calculated (see note); not specified by ISO 898. Use the values alongside our fastener catalog when selecting and specifying parts. ### How do I request a quotation? Use the parametric drawing on this page to set the exact configuration (size, material, finish) and click "Request this configuration" — a specialist from Engineering Hardware will respond within one business day.