M6 bolt torque specifications (8.8, 10.9, 12.9)
An M6 x 1 class 8.8 bolt takes 93 in-lb (10 N·m) dry, and class 10.9 takes 11 ft-lb (15 N·m). Both are for plain steel, dry threads (K 0.20) tightened to a clamp load of 75% of proof load.
Contents14 sections
Key takeaways
- Class 8.8 dry: 93 in-lb (10 N·m); class 10.9 dry: 11 ft-lb (15 N·m).
- M6 is where the chart switches units: 8.8 stays in in-lb, 10.9 and 12.9 cross 10 ft-lb.
- An M6 class 8.8 needs about 8% less torque than a 1/4-20 Grade 5 and clamps about 3% less.
- Zinc-plated 8.8 is 84 in-lb; with copper anti-seize it is 74 in-lb 1.
Quick facts
| Coarse thread | M6 x 1 (20.1 mm²) |
|---|---|
| Fine thread | M6 x 0.75 (22.0 mm²) |
| Wrench, ISO 4014/4017 | 10 mm |
| Wrench, DIN 931/933 | 10 mm (same) |
M6 bolt specifications
| Thread | Pitch | Tensile stress area |
|---|---|---|
| M6 x 1 (coarse) | 1 mm pitch | 20.1 mm² |
| M6 x 0.75 (fine) | 0.75 mm pitch | 22.0 mm² |
| Wrench, ISO 4014/4017 | 10 mm2 | |
Stress areas from ISO 898-1 Table 43.
M6 torque by grade
| Grade | Plain, dry K 0.202 | Lubricated K 0.152 | Clamp load |
|---|---|---|---|
| Class 4.6 | 36 in-lb4.1 N·m | 27 in-lb3.1 N·m | 3.4 kN |
| Class 8.8 | 93 in-lb10 N·m | 70 in-lb7.9 N·m | 8.7 kN |
| Class 10.9 | 11 ft-lb15 N·m | 100 in-lb11 N·m | 12.5 kN |
| Class 12.9 | 13 ft-lb18 N·m | 116 in-lb13 N·m | 14.6 kN |
Calculated with T = K × D × F, where F is 75% of the bolt’s proof load2 and K is the nut factor for each condition. Real preload from a torque wrench scatters by about ±25%4. When the equipment maker gives a torque, use theirs. How these numbers are made.
M6 4.6 torque
Proof 225 MPa · yield 240 MPa · tensile 400 MPa3. Clamp load at 75% of proof: 3.4 kN (M6 x 1).
| Condition | K | M6 x 1 | M6 x 0.75 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.202 | 36 in-lb4.1 N·m | 39 in-lb4.5 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.182 | 32 in-lb3.7 N·m | 35 in-lb4.0 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.152 | 27 in-lb3.1 N·m | 30 in-lb3.3 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.161 | 29 in-lb3.3 N·m | 32 in-lb3.6 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 20 in-lb2.2 N·m | 22 in-lb2.5 N·m |
M6 8.8 torque
Proof 580 MPa · yield 640 MPa · tensile 800 MPa3. Clamp load at 75% of proof: 8.7 kN (M6 x 1).
| Condition | K | M6 x 1 | M6 x 0.75 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.202 | 93 in-lb10 N·m | 102 in-lb11 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.182 | 84 in-lb9.4 N·m | 91 in-lb10 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.152 | 70 in-lb7.9 N·m | 76 in-lb8.6 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.161 | 74 in-lb8.4 N·m | 81 in-lb9.2 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 51 in-lb5.8 N·m | 56 in-lb6.3 N·m |
M6 10.9 torque
Proof 830 MPa · yield 940 MPa · tensile 1040 MPa3. Clamp load at 75% of proof: 12.5 kN (M6 x 1).
| Condition | K | M6 x 1 | M6 x 0.75 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.202 | 11 ft-lb15 N·m | 12 ft-lb16 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.182 | 120 in-lb14 N·m | 11 ft-lb15 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.152 | 100 in-lb11 N·m | 109 in-lb12 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.161 | 106 in-lb12 N·m | 116 in-lb13 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 73 in-lb8.3 N·m | 80 in-lb9.0 N·m |
M6 12.9 torque
Proof 970 MPa · yield 1100 MPa · tensile 1220 MPa3. Clamp load at 75% of proof: 14.6 kN (M6 x 1).
| Condition | K | M6 x 1 | M6 x 0.75 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.202 | 13 ft-lb18 N·m | 14 ft-lb19 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.182 | 12 ft-lb16 N·m | 13 ft-lb17 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.152 | 116 in-lb13 N·m | 11 ft-lb14 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.161 | 10 ft-lb14 N·m | 11 ft-lb15 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 85 in-lb9.7 N·m | 93 in-lb11 N·m |
Coarse or fine pitch
M6 x 1 is the coarse thread in the tables, with 20.1 mm² of stress area 3. The fine pitch, M6 x 0.75, is listed in the ISO 262 selected-sizes table 6; its 22.0 mm² is about 9.5% more. In class 8.8 dry the fine thread takes 102 in-lb instead of 93 in-lb and clamps 9.6 kN against 8.7 kN.
In-lb or ft-lb at M6
This is the size where the chart changes units. Class 8.8 dry is 7.7 ft-lb, so it is shown as 93 in-lb (10 N·m). Class 10.9 dry is 11 ft-lb (15 N·m) and 12.9 is 13 ft-lb (18 N·m), both past the 10 ft-lb point where the chart switches to ft-lb. Check which unit your wrench is set to: 93 ft-lb on an M6 would be twelve times the intended torque.
The 8.8 clamp load is 8.7 kN, about 1,970 lbf. At M8 the same class needs 19 ft-lb, about 2.4 times the M6 torque.
M6 next to 1/4 inch
M6 (6 mm) and 1/4 in (6.35 mm) are close in size but not the same thread. Calculated the same way, a 1/4-20 Grade 5 takes 101 in-lb dry against 93 in-lb for an M6 x 1 class 8.8: the M6 needs about 8% less torque and clamps about 3% less. Use the table for the thread you actually have.
Wrench size
An M6 hex head takes a 10 mm wrench in both ISO 4014/4017 and DIN 931/933 2.
Which class you have
ISO 898-1 calls for the property class and the maker’s mark on the head 3; see the bolt grades page. Class 10.9 dry torque is about 43% above 8.8 at M6, and class 4.6 drops to 36 in-lb (4.1 N·m).
When the chart does not apply
The dry figure is for plain steel. For class 8.8 M6, zinc plating (K 0.18) 2 gives 84 in-lb, oil (K 0.15) 2 gives 70 in-lb and copper or metal-free anti-seize (K 0.16) 1 gives 74 in-lb. Using 93 in-lb on an oiled M6 raises the clamp load by about a third. See dry vs lubricated torque. A torque published by the equipment maker takes priority over these values.
Sources
- 1
- 2
- 3
- 4
- 5Henkel Corporation (LOCTITE), LOCTITE LB 8012 Moly Paste TDS, April 2015Checked 21 Oct 2026
- 6Wikipedia, Wikipedia: ISO metric screw thread (ISO 262 selected sizes table)Checked 21 Oct 2026
Spotted a value that doesn’t match its source? Report an error
Related
- M5M5 x 0.8 bolt torque: 55 in-lb (6.2 N·m) for class 8.8 and 78 in-lb (8.8 N·m) for 10.9 dry, plus 12.9, M5 x 0.5 fine, oiled and moly paste.
- M8M8 x 1.25 bolt torque: 19 ft-lb (25 N·m) for class 8.8 and 27 ft-lb (36 N·m) for 10.9 dry, with 12.9, M8 x 1 fine, zinc and oiled values.
- 1/4 in1/4-20 Grade 5 bolt torque is 101 in-lb dry and Grade 8 is 12 ft-lb. Charts for 1/4-20 and 1/4-28 in Grade 2, 5 and 8, dry, zinc and oiled.
- Class 8.8Class 8.8 bolt torque from M3 to M30, dry, zinc-plated and lubricated, with the ISO 898-1 proof stress step from 580 MPa to 600 MPa above M16.
- Class 10.9Class 10.9 bolt torque from M3 to M30, dry, zinc-plated and lubricated, with ISO 898-1 strength (830 MPa proof) and how it compares with 8.8 and 12.9.
- Bolt torque calculatorBolt torque calculator for SAE and metric bolts by size, thread, grade and lubrication, using T = K × D × F with the proof loads from SAE J429 and ISO 898-1.
- Dry vs lubricated torqueWhy oiled bolts need less torque than dry ones for the same clamp load, with nut factor K values from Fastenal, NASA and Henkel for oil, zinc, anti-seize and moly.