ENGINEERING TOOL
M24 Bolt Torque Chart: Specs, Values & Settings
Class 8.8 · Target preload (kN) 158.1
| Dry / Black | 759 N·m 683–835 |
| Electro Zinc | 645 N·m 569–759 |
| Hot-Dip Galv. | 835 N·m 683–949 |
| Oiled | 493 N·m 455–569 |
M24 bolt torque spec: class 8.8 dry is 759 N·m (560 ft·lb). Values cover six property classes across five friction states — dry, zinc, HDG, oiled and anti-seize. K-factor method, basis fully disclosed.
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Torque by Property Class and Friction State
Quick answer: class 8.8 · dry / black ≈ 759 N·m (683–835); 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 | 84 | 403 363–444 | 343 302–403 | 444 363–504 | 262 242–302 | 202 161–242 |
| 8.8 | 640 | 158.1 | 759 683–835 | 645 569–759 | 835 683–949 | 493 455–569 | 380 304–455 |
| 10.9 | 940 | 232.3 | 1115 1003–1226 | 948 836–1115 | 1226 1003–1394 | 725 669–836 | 557 446–669 |
| 12.9 | 1100 | 271.8 | 1305 1174–1435 | 1109 979–1305 | 1435 1174–1631 | 848 783–979 | 652 522–783 |
| A2-70 | 450 | 111.2 | 534 480–587 | 454 400–534 | 587 480–667 | 347 320–400 | 267 213–320 |
| A4-80 | 600 | 148.3 | 712 640–783 | 605 534–712 | 783 640–890 | 463 427–534 | 356 285–427 |
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 (M24 × 2 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 M24 As = 384 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 | 91.4 | 439 395–483 | 373 329–439 | 483 395–548 | 285 263–329 | 219 175–263 |
| 8.8 | 640 | 172 | 826 743–908 | 702 619–826 | 908 743–1032 | 537 495–619 | 413 330–495 |
| 10.9 | 940 | 252.7 | 1213 1092–1334 | 1031 910–1213 | 1334 1092–1516 | 788 728–910 | 606 485–728 |
| 12.9 | 1100 | 295.7 | 1419 1277–1561 | 1206 1064–1419 | 1561 1277–1774 | 923 852–1064 | 710 568–852 |
| A2-70 | 450 | 121 | 581 523–639 | 494 435–581 | 639 523–726 | 377 348–435 | 290 232–348 |
| A4-80 | 600 | 161.3 | 774 697–852 | 658 581–774 | 852 697–968 | 503 464–581 | 387 310–464 |
Cell shows the typical value; the small line below is the range (min–max).
Basis of Calculation & Sources
Calculation basis
- 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 (M24 As = 353 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).
Scope & limits
- 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.
Cite this chart
YAXIIO. M24 Bolt Torque Chart: Specs, Values & Settings. https://www.yaxiio.com/en/tools/bolt-torque-chart/m24 (accessed 2026-10-29).
Free to cite and embed — attribution required: “YAXIIO” + a link to this page.
FAQ
What is the target preload for an M24 bolt?
At 70% of Rp0.2: class 4.8 ≈ 84 kN, 8.8 ≈ 158.1 kN, 10.9 ≈ 232.3 kN; stainless A2-70 ≈ 111.2 kN and A4-80 ≈ 148.3 kN.
Can I use carbon-steel torque values for stainless M24 (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).
Next: work out your order, or pick the size by standard
Related References
Bolt Torque Calculator
Interactive version: fine threads, imperial, stud bolts, custom K and torque check — this size is pre-filled.
M24 Hex Bolt Weight Chart
Per-piece and per-1,000-pcs weights across the full length series of the same size.
M24 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.
Tap Drill for the Thread Being Tightened
The hole under the bolt: rule tap drill value plus the nearest drill bit in the set, stated ahead of the torque tables.
Disclaimer: This chart is an engineering estimation for selection and budgeting only. It does not constitute assembly instructions or acceptance criteria.