ENGINEERING TOOL
M14 Bolt Torque Chart
Target preload and tightening torque ranges (min–typ–max) for M14 bolts across six property classes and five friction states. K-factor method, basis fully disclosed.
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Torque by Property Class and Friction State
Quick answer: class 8.8 · electro zinc ≈ 123 N·m (108–144); other classes and friction states below.
| Class | Rp0.2 (MPa) | Target preload (kN) | Dry / Black K 0.18–0.22 · N·m | Electro Zinc K 0.15–0.2 · N·m | Hot-Dip Galv. K 0.18–0.25 · N·m | Oiled K 0.12–0.15 · N·m | Wax / PTFE / Anti-seize K 0.08–0.12 · N·m |
|---|---|---|---|---|---|---|---|
| 4.8 | 340 | 27.4 | 77 69–84 | 65 57–77 | 84 69–96 | 50 46–57 | 38 31–46 |
| 8.8 | 640 | 51.5 | 144 130–159 | 123 108–144 | 159 130–180 | 94 87–108 | 72 58–87 |
| 10.9 | 940 | 75.7 | 212 191–233 | 180 159–212 | 233 191–265 | 138 127–159 | 106 85–127 |
| 12.9 | 1100 | 88.6 | 248 223–273 | 211 186–248 | 273 223–310 | 161 149–186 | 124 99–149 |
| A2-70 | 450 | 36.2 | 101 91–112 | 86 76–101 | 112 91–127 | 66 61–76 | 51 41–61 |
| A4-80 | 600 | 48.3 | 135 122–149 | 115 101–135 | 149 122–169 | 88 81–101 | 68 54–81 |
Cell shows the typical value; the small line below is the range (min–max).
References
- ISO 898-1:2013 — Mechanical properties of fasteners made of carbon and alloy steel
- ISO 3506-1:2020 — Mechanical properties of corrosion-resistant stainless steel fasteners (A2/A4)
- GB/T 3098.1-2010 — Mechanical properties of bolts, screws and studs (CN national standard, official full text)
- GB/T 3098.6-2014 — Mechanical properties of stainless steel bolts, screws and studs (CN, official full text)
- ISO 16047:2005 — Fasteners: torque/clamp force testing (K-factor measurement method)
- Machinery's Handbook (30th ed.) — empirical K-factor ranges
- Machine Design — anti-seize compound friction test (K≈0.10)
Fine-Thread Torque Matrix
Fine-thread series (M14 × 1.5 mm) target preload and tightening torque ranges, same basis as the coarse chart; the fine-thread stress area As follows ISO 898-1:2013 Table 6 (this page takes M14 As = 125 mm²).
| Class | Rp0.2 (MPa) | Target preload (kN) | Dry / Black K 0.18–0.22 · N·m | Electro Zinc K 0.15–0.2 · N·m | Hot-Dip Galv. K 0.18–0.25 · N·m | Oiled K 0.12–0.15 · N·m | Wax / PTFE / Anti-seize K 0.08–0.12 · N·m |
|---|---|---|---|---|---|---|---|
| 4.8 | 340 | 29.7 | 83 75–92 | 71 62–83 | 92 75–104 | 54 50–62 | 42 33–50 |
| 8.8 | 640 | 56 | 157 141–172 | 133 118–157 | 172 141–196 | 102 94–118 | 78 63–94 |
| 10.9 | 940 | 82.3 | 230 207–253 | 196 173–230 | 253 207–288 | 150 138–173 | 115 92–138 |
| 12.9 | 1100 | 96.3 | 270 243–296 | 229 202–270 | 296 243–337 | 175 162–202 | 135 108–162 |
| A2-70 | 450 | 39.4 | 110 99–121 | 94 83–110 | 121 99–138 | 72 66–83 | 55 44–66 |
| A4-80 | 600 | 52.5 | 147 132–162 | 125 110–147 | 162 132–184 | 96 88–110 | 74 59–88 |
Cell shows the typical value; the small line below is the range (min–max).
Basis of Calculation & Sources
Torque follows the K-factor (nut factor) method T = K·D·F: D is the nominal diameter and F the target preload = 70% of Rp0.2 × thread stress area (M14 As = 115 mm²). Yield strengths are published values from ISO 898-1 (carbon/alloy steel) and ISO 3506-1 (stainless A2/A4). K follows published empirical ranges per friction condition (Machinery's Handbook; the wax/PTFE/anti-seize band K≈0.10 follows Machine Design test data). The grease/MoS₂ band (K≈0.11) nearly overlaps anti-seize and is available in the calculator instead of a separate column.
Stainless note: A2/A4 austenitic thread pairs gall easily under frictional heating. Always apply anti-seize and follow the Wax/PTFE/Anti-seize column (K≈0.10).
Boundary: this chart is a simplified K-factor estimate, not a full VDI 2230 analysis (which accounts for joint resilience, embedment and assembly method). Friction is the dominant variable — no single torque value exists without its friction state. Always follow the design specification or manufacturer torque table.
Corresponding standard page
Open the GB/T 5783 / DIN 933 standard product page: sizes, materials and finishes, and ordering questions.
Open the GB/T 5783 / DIN 933 page
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FAQ
What is the tightening torque for an M14 class 8.8 bolt?
It depends on the friction state (typical values at 70% of Rp0.2 target preload): oiled ≈ 94 N·m, electro zinc ≈ 123 N·m, hot-dip galvanized ≈ 159 N·m, dry/black ≈ 144 N·m, anti-seize ≈ 72 N·m. See the matrix above for ranges — no single torque value exists without its friction state.
What is the target preload for an M14 bolt?
At 70% of Rp0.2: class 4.8 ≈ 27.4 kN, 8.8 ≈ 51.5 kN, 10.9 ≈ 75.7 kN; stainless A2-70 ≈ 36.2 kN and A4-80 ≈ 48.3 kN.
Can I use carbon-steel torque values for stainless M14 (A2-70/A4-80)?
No. The classes have different yield strengths (A2-70 = 450 MPa, A4-80 = 600 MPa), so target preloads differ; and stainless thread pairs gall easily — always apply anti-seize and follow the Wax/PTFE/Anti-seize column (K≈0.10).
What basis are these torque values calculated on?
The K-factor method T = K·D·F with target preload = 70% of Rp0.2 × stress area (yield strengths per ISO 898-1 / ISO 3506-1 published values) and K per published empirical friction ranges. Estimated values, not assembly instructions; run a full VDI 2230 analysis for critical joints.
Related References
Bolt Torque Calculator
Interactive version: fine threads, imperial, stud bolts, custom K and torque check — this size is pre-filled.
Metric Bolt Torque Chart (Reference)
Full M6–M36 tables with disclosed formula and GB/ISO clause citations; every value reproducible.
M14 Hex Bolt Weight Chart
Per-piece and per-1,000-pcs weights across the full length series of the same size.
M14 Hex Key Size Chart
Which hex key (Allen wrench) fits a socket head cap screw of the same size: socket width across flats, key long and short arm lengths, and unit weight on the GB/T 70.1 + GB/T 5356 basis.
Disclaimer: This chart is an engineering estimation for selection and budgeting only. It does not constitute assembly instructions or acceptance criteria.