SAE bolt torque chart (Grade 2, 5 and 8)
A 1/2-13 Grade 5 bolt takes 75 ft-lb plain and dry or 57 ft-lb with oiled threads; Grade 8 in the same size takes 107 or 80 ft-lb. The chart covers coarse threads from 1/4 in to 1 in, at 75% of proof load.
Contents7 sections
Key takeaways
- Dry values use K 0.20 and oiled values K 0.15, both at 75% of proof load 1.
- Grade 8 takes about 41% more torque than Grade 5 in every size on the chart.
- Grade 2 strength drops above 3/4 in, so a 7/8 in Grade 2 bolt takes less torque than a 3/4 in one 1.
- Do not use these values for pretensioned structural joints 2.
Quick facts
| Sizes | 1/4 in to 1 in, UNC |
|---|---|
| Clamp basis | 75% of SAE J429 proof load |
| Dry / oiled K | 0.20 / 0.15 |
SAE bolt torque chart (ft-lb / in-lb)
Coarse thread, clamp load 75% of proof load. Dry is plain steel K 0.201; oiled is a lubricated thread K 0.151. Fine threads, zinc-plated and anti-seize values are on each size page.
| Size | Grade 2 | Grade 5 | Grade 8 | |||
|---|---|---|---|---|---|---|
| Dry | Oiled | Dry | Oiled | Dry | Oiled | |
| 1/4-20 | 66 in-lb | 49 in-lb | 101 in-lb | 76 in-lb | 12 ft-lb | 107 in-lb |
| 5/16-18 | 11 ft-lb | 102 in-lb | 17 ft-lb | 13 ft-lb | 25 ft-lb | 18 ft-lb |
| 3/8-16 | 20 ft-lb | 15 ft-lb | 31 ft-lb | 23 ft-lb | 44 ft-lb | 33 ft-lb |
| 7/16-14 | 32 ft-lb | 24 ft-lb | 49 ft-lb | 37 ft-lb | 70 ft-lb | 52 ft-lb |
| 1/2-13 | 49 ft-lb | 37 ft-lb | 75 ft-lb | 57 ft-lb | 107 ft-lb | 80 ft-lb |
| 9/16-12 | 70 ft-lb | 53 ft-lb | 109 ft-lb | 82 ft-lb | 154 ft-lb | 115 ft-lb |
| 5/8-11 | 97 ft-lb | 73 ft-lb | 150 ft-lb | 113 ft-lb | 212 ft-lb | 159 ft-lb |
| 3/4-10 | 173 ft-lb | 130 ft-lb | 267 ft-lb | 200 ft-lb | 377 ft-lb | 283 ft-lb |
| 7/8-9 | 167 ft-lb | 125 ft-lb | 430 ft-lb | 322 ft-lb | 606 ft-lb | 455 ft-lb |
| 1-8 | 250 ft-lb | 187 ft-lb | 644 ft-lb | 483 ft-lb | 909 ft-lb | 682 ft-lb |
SAE bolt torque chart (N·m)
| Size | Grade 2 | Grade 5 | Grade 8 | |||
|---|---|---|---|---|---|---|
| Dry | Oiled | Dry | Oiled | Dry | Oiled | |
| 1/4-20 | 7.4 N·m | 5.6 N·m | 11 N·m | 8.6 N·m | 16 N·m | 12 N·m |
| 5/16-18 | 15 N·m | 11 N·m | 24 N·m | 18 N·m | 33 N·m | 25 N·m |
| 3/8-16 | 27 N·m | 20 N·m | 42 N·m | 31 N·m | 59 N·m | 44 N·m |
| 7/16-14 | 43 N·m | 32 N·m | 67 N·m | 50 N·m | 94 N·m | 71 N·m |
| 1/2-13 | 66 N·m | 50 N·m | 102 N·m | 77 N·m | 144 N·m | 108 N·m |
| 9/16-12 | 95 N·m | 72 N·m | 147 N·m | 111 N·m | 208 N·m | 156 N·m |
| 5/8-11 | 132 N·m | 99 N·m | 203 N·m | 153 N·m | 287 N·m | 215 N·m |
| 3/4-10 | 234 N·m | 176 N·m | 362 N·m | 271 N·m | 511 N·m | 383 N·m |
| 7/8-9 | 226 N·m | 170 N·m | 582 N·m | 437 N·m | 822 N·m | 617 N·m |
| 1-8 | 339 N·m | 254 N·m | 873 N·m | 655 N·m | 1,232 N·m | 924 N·m |
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%3. When the equipment maker gives a torque, use theirs. How these numbers are made.
How to read the chart
Find the bolt size in the left column, then the grade column, then pick Dry or Oiled to match the threads you have. Dry means plain steel, clean and with no lubricant. Oiled means oil or grease on the threads and under the nut or head 1. For zinc-plated bolts, anti-seize or fine threads, open the size page. Each one lists every condition for both UNC and UNF.
Sizes under 10 ft-lb are shown in in-lb. A 1/4-20 Grade 5 bolt is 101 in-lb dry. Setting that number on a ft-lb wrench would be 12 times too much.
The grade steps are not even. Grade 5 proof load is 85 ksi against 55 ksi for Grade 2 up to 3/4 in, so Grade 5 takes about 55% more torque in those sizes. Above 3/4 in, Grade 2 proof falls to 33 ksi 1. That makes the 7/8-9 Grade 2 value (167 ft-lb) lower than the 3/4-10 value (173 ft-lb). It is also why Grade 5 needs about 2.6 times the Grade 2 torque at 7/8 and 1 in.
Why SAE charts disagree
Two charts can both be right and still differ by 25% or more, because they assume different conditions:
- Dry or lubricated. For a 1/2-13 Grade 8 bolt, 107 ft-lb dry and 80 ft-lb oiled give the same clamp load. Many published charts print the lubricated figure without saying so. If you read it as a dry value, you get about 25% less clamp load than you meant to.
- Clamp basis. Some charts target 75% of proof load. Others use a share of yield, or 90% of proof for special applications such as structural bolts 1. For Grades 5 and 8, 70% of yield and 75% of proof come within about 1% of each other. A chart built on 85% of proof is about 13% higher.
- Nut factor. K is not a friction coefficient. It lumps thread friction, underhead friction and geometry together 1. NASA notes that 0.20 is the common assumption but that 0.15 is more realistic for steel on steel 3.
Even with the right K, torque control leaves about ±25% scatter in bolt tension 3.
When not to use this chart
- Structural bolts in pretensioned or slip-critical joints. RCSC forbids torque taken from tables or equations without verification 2. See A325 bolts.
- A published spec from the equipment maker. Use the maker’s value.
- A weaker nut or tapped hole. The table assumes a nut whose proof strength is at least the bolt’s tensile strength 1. A Grade 5 nut on a Grade 8 bolt does not meet that.
- Waxed threads. NASA says to cut dry table torque by 50% for wax 3.
Sources
- 1
- 2
- 3
Spotted a value that doesn’t match its source? Report an error
Related
- Metric chartMetric bolt torque chart for classes 4.6, 8.8, 10.9 and 12.9 from M3 to M30, dry and lubricated, in N·m and ft-lb from ISO 898-1 proof loads.
- 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.
- 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.