1 inch bolt torque specifications (Grade 2, 5, 8)
A 1-8 Grade 5 bolt takes 644 ft-lb (873 N·m) and a Grade 8 takes 909 ft-lb (1,232 N·m). Both values are for plain, dry steel threads (K 0.20) tightened to 75% of proof load.
Contents12 sections
Key takeaways
- 1 in is the largest size where Grade 5 keeps 85,000 psi proof; above 1 in it drops to 74,000 psi 1.
- Grade 2 is on its lower 33,000 psi row here 1, so a Grade 5 carries 2.6 times its clamp load.
- Oiled threads need 25% less torque for the same clamp load (K 0.15 vs 0.20) 1: 483 ft-lb for Grade 5, 682 ft-lb for Grade 8.
- 1-12 fine thread carries 9.4% more clamp load than 1-8, the smallest gain of any size from 1/4 to 1 in.
Quick facts
| Coarse thread | 1-8 UNC |
|---|---|
| Fine thread | 1-12 UNF |
| Wrench, hex cap screw and nut | 1-1/2 in |
| Wrench, heavy hex bolt | 1-5/8 in |
1 in bolt specifications
| Thread | Pitch | Tensile stress area |
|---|---|---|
| 1-8 (UNC) | 8 threads per inch | 0.6060 in² |
| 1-12 (UNF) | 12 threads per inch | 0.6630 in² |
| Wrench, hex cap screw | 1-1/2 in1 | |
| Wrench, heavy hex (structural) | 1-5/8 in | |
Stress areas from ASME B1.1 as tabulated by Fastenal1.
1 in torque by grade
| Grade | Plain, dry K 0.201 | Lubricated K 0.151 | Clamp load |
|---|---|---|---|
| Grade 2 | 250 ft-lb339 N·m | 187 ft-lb254 N·m | 15,000 lbf |
| Grade 5 | 644 ft-lb873 N·m | 483 ft-lb655 N·m | 38,630 lbf |
| Grade 8 | 909 ft-lb1,232 N·m | 682 ft-lb924 N·m | 54,540 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.
1 in Grade 2 torque
Proof 33,000 psi · yield 36,000 psi · tensile 60,000 psi1. Clamp load at 75% of proof: 15,000 lbf (1-8).
| Condition | K | 1-8 | 1-12 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 250 ft-lb339 N·m | 273 ft-lb371 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 225 ft-lb305 N·m | 246 ft-lb334 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 187 ft-lb254 N·m | 205 ft-lb278 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.163 | 200 ft-lb271 N·m | 219 ft-lb297 N·m |
| Moly pasteMolybdenum disulfide paste | 0.114 | 137 ft-lb186 N·m | 150 ft-lb204 N·m |
1 in Grade 5 torque
Proof 85,000 psi · yield 92,000 psi · tensile 120,000 psi1. Clamp load at 75% of proof: 38,630 lbf (1-8).
| Condition | K | 1-8 | 1-12 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 644 ft-lb873 N·m | 704 ft-lb955 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 579 ft-lb786 N·m | 634 ft-lb860 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 483 ft-lb655 N·m | 528 ft-lb716 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.163 | 515 ft-lb698 N·m | 564 ft-lb764 N·m |
| Moly pasteMolybdenum disulfide paste | 0.114 | 354 ft-lb480 N·m | 387 ft-lb525 N·m |
1 in Grade 8 torque
Proof 120,000 psi · yield 130,000 psi · tensile 150,000 psi1. Clamp load at 75% of proof: 54,540 lbf (1-8).
| Condition | K | 1-8 | 1-12 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 909 ft-lb1,232 N·m | 995 ft-lb1,348 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 818 ft-lb1,109 N·m | 895 ft-lb1,214 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 682 ft-lb924 N·m | 746 ft-lb1,011 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.163 | 727 ft-lb986 N·m | 796 ft-lb1,079 N·m |
| Moly pasteMolybdenum disulfide paste | 0.114 | 500 ft-lb678 N·m | 547 ft-lb742 N·m |
Strength breaks around 1 in
Two of the three SAE J429 grades change strength near this size, per the Fastenal reproduction of the standard 1:
- Grade 2 has been on its lower row since 7/8 in: 33,000 psi proof, against 55,000 psi at 3/4 in and below.
- Grade 5 keeps 85,000 psi proof up to and including 1 in. Above 1 in it is rated at 74,000 psi, about 13% lower.
- Grade 8 stays at 120,000 psi through 1-1/2 in.
So at 1 in the grades are far apart. Dry 1-8 torques run 250 ft-lb for Grade 2, 644 for Grade 5 and 909 for Grade 8; the Grade 5 clamp of 38,630 lbf is 2.6 times the Grade 2 figure of 15,000 lbf. Grade 8.2, a boron-steel grade, is listed with the same 120,000 psi proof as Grade 8 for sizes up to 1 in 1. If you move to a 1-1/8 in Grade 5 bolt, do not scale this page up; the lower proof stress applies.
Coarse or fine thread
The 1-8 coarse thread has a tensile stress area of 0.606 in²; the 1-12 fine thread has 0.663 in² 1. That 9.4% gain is the smallest from 1/4 to 1 in (1/4 in gains 14.5%). The fine thread needs 704 against 644 ft-lb in Grade 5 dry, and 995 against 909 ft-lb in Grade 8.
Which grade you have
Grade 2 heads are plain, Grade 5 has three radial lines and Grade 8 six 1. Use a Grade 5 nut on a Grade 5 bolt and a Grade 8 nut on a Grade 8 bolt 1. The grades page shows the markings.
Structural bolts at 1 in
A325 and A490 heavy hex bolts of this diameter are pretensioned to RCSC minimums of 51 kips and 64 kips 5, not torqued from a chart; RCSC bans unverified table torques for calibrated-wrench installation 5. Under ASTM F3125, A325 is 120 ksi minimum tensile at every size to 1-1/2 in; the older A325 stepped down above 1 in 6. See A325 bolt torque and ASTM F3125.
When the chart does not apply
The values size clamp load to the bolt’s proof load with the K in each row. They do not check whether the clamped parts or a tapped hole can carry 15,000 to 60,000 lbf, and preload from a torque wrench scatters by about ±25% 2. When the equipment maker gives a torque, use the maker’s value.
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
- 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.
- SAE chartSAE bolt torque chart for Grade 2, 5 and 8 from 1/4 in to 1 in, dry and lubricated, calculated from SAE J429 proof loads with the nut factor shown.
- 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.
- ASTM F3125ASTM F3125 replaced A325, A325M, A490, A490M, F1852 and F2280. Grades, 120 and 150 ksi strengths, sizes, types and the head markings RCSC requires.
- 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.