3/4 inch bolt torque specifications (Grade 2, 5, 8)
A 3/4-10 Grade 5 bolt takes 267 ft-lb (362 N·m) and a Grade 8 takes 377 ft-lb (511 N·m). Both values are for plain, dry steel threads (K 0.20) tightened to 75% of proof load.
Contents11 sections
Key takeaways
- 3/4 in is the largest size where Grade 2 keeps its 55,000 psi proof stress; from 7/8 in it drops to 33,000 psi 1.
- Oiled threads need 25% less torque for the same clamp load (K 0.15 vs 0.20) 1: 200 ft-lb for Grade 5, 283 ft-lb for Grade 8.
- 3/4-16 fine thread carries 11.3% more clamp load than 3/4-10 (23,780 against 21,360 lbf in Grade 5).
- Hex cap screw and nut 1-1/8 in; structural heavy hex 1-1/4 in 1.
Quick facts
| Coarse thread | 3/4-10 UNC |
|---|---|
| Fine thread | 3/4-16 UNF |
| Wrench, hex cap screw and nut | 1-1/8 in |
| Wrench, heavy hex bolt | 1-1/4 in |
3/4 in bolt specifications
| Thread | Pitch | Tensile stress area |
|---|---|---|
| 3/4-10 (UNC) | 10 threads per inch | 0.3350 in² |
| 3/4-16 (UNF) | 16 threads per inch | 0.3730 in² |
| Wrench, hex cap screw | 1-1/8 in1 | |
| Wrench, heavy hex (structural) | 1-1/4 in | |
Stress areas from ASME B1.1 as tabulated by Fastenal1.
3/4 in torque by grade
| Grade | Plain, dry K 0.201 | Lubricated K 0.151 | Clamp load |
|---|---|---|---|
| Grade 2 | 173 ft-lb234 N·m | 130 ft-lb176 N·m | 13,820 lbf |
| Grade 5 | 267 ft-lb362 N·m | 200 ft-lb271 N·m | 21,360 lbf |
| Grade 8 | 377 ft-lb511 N·m | 283 ft-lb383 N·m | 30,150 lbf |
Calculated with T = K × D × F, where F is 75% of the bolt’s proof load1 and K is the nut factor for each condition. Real preload from a torque wrench scatters by about ±25%2. When the equipment maker gives a torque, use theirs. How these numbers are made.
3/4 in Grade 2 torque
Proof 55,000 psi · yield 57,000 psi · tensile 74,000 psi1. Clamp load at 75% of proof: 13,820 lbf (3/4-10).
| Condition | K | 3/4-10 | 3/4-16 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 173 ft-lb234 N·m | 192 ft-lb261 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 155 ft-lb211 N·m | 173 ft-lb235 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 130 ft-lb176 N·m | 144 ft-lb196 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.163 | 138 ft-lb187 N·m | 154 ft-lb209 N·m |
| Moly pasteMolybdenum disulfide paste | 0.114 | 95 ft-lb129 N·m | 106 ft-lb143 N·m |
3/4 in Grade 5 torque
Proof 85,000 psi · yield 92,000 psi · tensile 120,000 psi1. Clamp load at 75% of proof: 21,360 lbf (3/4-10).
| Condition | K | 3/4-10 | 3/4-16 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 267 ft-lb362 N·m | 297 ft-lb403 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 240 ft-lb326 N·m | 268 ft-lb363 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 200 ft-lb271 N·m | 223 ft-lb302 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.163 | 214 ft-lb290 N·m | 238 ft-lb322 N·m |
| Moly pasteMolybdenum disulfide paste | 0.114 | 147 ft-lb199 N·m | 163 ft-lb222 N·m |
3/4 in Grade 8 torque
Proof 120,000 psi · yield 130,000 psi · tensile 150,000 psi1. Clamp load at 75% of proof: 30,150 lbf (3/4-10).
| Condition | K | 3/4-10 | 3/4-16 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 377 ft-lb511 N·m | 420 ft-lb569 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 339 ft-lb460 N·m | 378 ft-lb512 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 283 ft-lb383 N·m | 315 ft-lb427 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.163 | 302 ft-lb409 N·m | 336 ft-lb455 N·m |
| Moly pasteMolybdenum disulfide paste | 0.114 | 207 ft-lb281 N·m | 231 ft-lb313 N·m |
Coarse or fine thread
The 3/4-10 coarse thread has a tensile stress area of 0.335 in² and the 3/4-16 fine thread 0.373 in² 1. The fine thread carries 11.3% more clamp load at the same stress, and its torque is higher by the same ratio: 297 against 267 ft-lb in Grade 5 dry, 420 against 377 ft-lb in Grade 8.
The coarse figure is Fastenal’s printed value; the ASME B1.1 formula gives 0.3345 in² 5. The 0.15% difference does not move any rounded torque here.
Which grade you have
Grade 2 heads are plain, Grade 5 shows three radial lines and Grade 8 six 1. At 3/4 in the proof stresses are 55,000, 85,000 and 120,000 psi 1, giving dry torques of 173, 267 and 377 ft-lb.
This is the last size where Grade 2 sits on its higher strength row. SAE J429 drops Grade 2 to 33,000 psi proof above 3/4 in 1, so a 7/8-9 Grade 2 is calculated at 167 ft-lb, less than the 3/4-10 Grade 2 at 173 ft-lb even though the bolt is larger. Do not scale a 3/4 in Grade 2 value up to the next size. Match the nut: Grade 5 nut on a Grade 5 bolt, Grade 8 nut on a Grade 8 bolt 1. The grades page shows the markings.
Structural bolts at 3/4 in
A325 and A490 heavy hex bolts of this diameter are pretensioned to RCSC minimums, not torqued from a chart: 28 kips for A325 and 35 kips for A490 6. The A325 figure falls between the Grade 5 chart clamp (21,360 lbf) and the Grade 8 one (30,150 lbf). For calibrated-wrench installation RCSC bans torque values from tables or equations that have not been verified 6, and it does not permit zinc coating of A490 bolts 6. See A325 bolt torque and A490 bolt torque.
When the chart does not apply
The values size clamp load to the bolt’s proof load with the K shown in each row. They do not check whether the clamped parts or a tapped hole can take 14,000 to 34,000 lbf of clamp, and NASA warns that the default K of 0.20 “should not be used blindly” 2. Preload from a torque wrench also scatters by about ±25% 2. When the equipment maker gives a torque, use the maker’s value; for lubricated threads see dry vs lubricated torque.
Sources
- 1
- 2
- 3
- 4Henkel Corporation (LOCTITE), LOCTITE LB 8012 Moly Paste TDS, April 2015Checked 21 Oct 2026
- 5
- 6
Spotted a value that doesn’t match its source? Report an error
Related
- 5/8 in5/8-11 Grade 5 bolt torque is 150 ft-lb dry and Grade 8 is 212 ft-lb. Charts for 5/8-11 and 5/8-18 in Grade 2, 5 and 8, dry, zinc-plated and oiled.
- 7/8 in7/8-9 Grade 5 bolt torque is 430 ft-lb dry and Grade 8 is 606 ft-lb. Grade 2 drops to a lower strength at this size. 7/8-9 and 7/8-14 charts.
- Grade 5Grade 5 bolt torque from 1/4 in to 1 in, dry, zinc-plated and lubricated, with SAE J429 strength, the three-line head mark and the step down to 74 ksi above 1 in.
- Grade 8Grade 8 bolt torque from 1/4 in to 1 in, dry, zinc-plated and lubricated, with SAE J429 proof, yield and tensile strength and the six-line head marking.
- Grade 2Grade 2 bolt torque from 1/4 in to 1 in, dry, zinc-plated and lubricated, with SAE J429 strength, the drop to 33 ksi proof above 3/4 in, and the plain-head marking.
- A325A325 bolts have no RCSC torque value. Minimum pretension is 28 kips for 3/4 in and 51 kips for 1 in; the torque is found daily on the job for each wrench.
- A490A490 bolts have no RCSC torque value. Minimum pretension is 35 kips for 3/4 in and 64 kips for 1 in; RCSC bans galvanizing and reuse of A490 heavy hex bolts.
- 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.