Bolt Torque Chart: SAE Grade 2, 5 and 8 Tightening Torque Table (Free PDF)

Bolt size: Locate your bolt diameter in the Bolt size column.

TPI: Check that your fastener has the same threads per inch as listed here

Grade: Under your bolt’s grade, look at the torque value. In this chart, all bolts is assumed to be plain, dry and not plated.

The K factor for nut friction is 0.20.

Bolt is clamped with a clamp load equal to 75% of the SAE J429 proof load.

First three torque columns are in foot-pounds. Last three are the same numbers, except expressed in newton-metres. This allows you to use metric torque wrenches.

Radial Marks

It is Grade 2. There are no radial marks. It is Grade 5. There are three radial dashes. It is Grade 8. There is six radial dashes.

Torque

Industry Formula:  T = K x D x F        K = friction factor. D = Nominal Diameter. F = Target Clamp Load.

The torque for bolts with 1/4 and 5/16 inch diameters is small. They are quoted in inch-pounds in most published charts. In this case 5.5 ft-lb = 66 in-lb

The largest pitfall of all on any torque chart is the Friction Factor K. Tables published will vary based off the value of K used. For example some charts call out K=0.15 for lubricated bolts while others says K=0.17 or even 0.18 for zinc plated bolts. That alters all numbers 10 to 25%. You should of not grab a value for dry bolts from one chart and a value for lubricated bolts from another chart.

Another trap is grade 2 over 3/4 in. SAE J429 reduces proof stress from 55,000 to 33,000 psi. So a properly sized 7/8 inch Grade 2 bolt requires less torque then a 3/4 inch one does. The grade 2 values are limited to fasteners up to 6 inches in length.

The bolt tension is indirectly represented by torque. Friction eats about 85 to 90% of it. That’s where the nut meets the bar stock as well as inside the threads. The rest stretch the bolt.

It’s not so much about the wrench but the condition. Threads need to be undamaged and clean. Apply a hardened steel washer underneath whatever you are turning. Squeeze the wrench smoothly and slowly to get to the target number.

The table above no longer applies if you have a nylock insert nut or if the assembly is waxed, plated, or has oil on it.

Don't try to apply it to stainless bolts. Stainless is made differently and will gall. See the table below for stainless steel information.

Don't use it on structural A325 or A490 connections. That's governed by RCSC rules. Refer to the structural table.

Don't use it on soft or gasketed joints. Don't use it on tapped aluminum. Internal torque is often limited because of this.

For metric fasteners see our dedicated metric bolt torque chart which includes classes 8.8, 10.9, and 12.9. It uses the same mu = 0.14 basis.

A torque value stamped in an equipment maker's manual replaces all generic charts including this one in each and every case.

The UNF or Fine Thread torque table is the one above.

Like coarse thread table, it is based off assumed dry, plain steel with a K factor of 0.20. Clamp load is at 75% SAE J429 proof load. Find thread size in the left hand column. This combines both diameter and TPI.

So perhaps you’re searching for 1/2-20. Read across to get your value in ft-lb. There are also the values in Nm in the final three columns.

Fine threads has a greater tensile stress area than equally sized coarse threads. In other words, they carry about 8 to 14% more preload. Consequently they require proportionally more torque. A 1/2-20 Grade 8 bolt requires 120 ft-lb. Only 106 ft-lb are required for a 1/2-13 bolt.

Fine threads shed less torque to the thread ramp. Fine threads also resist vibration loosening slightly better. Fine threads permit finer adjustment. Automotive work commonly use fine threads because of this.

Know your 1's (rows). The real UNF 1 in thread is actualy 1-12. But back in the day, older US equipment often used a legacy 1-14 UNS thread that has been around awhile. That legacy thread will takes a slightly different torque. It also has a different stress area compared to the UNF standard.

Always check the TPI before selecting a row. For sizes above 1 in., the UNF series is all 12 TPI. So it includes 1-1/8-12, 1-1/4-12, 1-3/8-12, 1-1/2-12.

The Grade 2 proof stress declines from 55,000 to 33,000 psi above 3/4 in. That cause the Grade 2 column to drop. From 3/4-16 it goes from 192 ft-lb to 184 at 7/8-14.

Fine thread Grade 2 bolts don’t come large. Many charts of main distributors ends their Grade 2 fine values at 1 in. Those rows show our calculated values. We applied the published J429 proof loads and K = 0.20 formula as before. You should of exercise them with your usual engineering caution.

It’s not for plated or lubricated fasteners. For lubricated fasteners, see the lubricated table below. It’s not for stainless steel. It’s not for metric fine pitch threads like M12x1.25. That’s covered in the metric bolt torque chart.

If your machine has a service manual and a torque figure stamped on it, use the figure stamped there. In that case, don’t use this chart.

This table applies when the nut bearing face carries cutting fluid, light grease or oil. It has the same 75% proof load target as above (K = 0.15) but uses that as its base. Therefore, every figure above is three quarters of the value under K = 0.20 (dry).

There is only one table but it stacks UNC and UNF together. Check the Series column so you don't read a coarse value for a fine thread.

This reduces because the torque isn't tension, but tension plus friction. Friction is cut by oil, so more of every foot-pound becomes tension pulling on the bolt.

Applying a dry chart value to an oiled bolt will land the clamp load about a third high, which can push a Grade 8 past its proof load and cause it to yield or snap. It’s the single most common way good bolts gets broken with a calibrated wrench.

Ordinary machine oil has K = 0.15. The stronger the lubricant, the farther it go.

Anti-seize pastes with moly or copper gets you down to K = 0.12 or less. Waxing the plating gets you even further: K = 0.10. For such products, knock another 15, 25 % off this table’s figures or do as directed by the paste maker.

Dry hardware zinc plated is in-between the two tables, roughly K = 0.17 to 0.18. The 0.17 is what Fastenal gives it for K.

Always lubricate. Lubricate under the turned element, on its threads, and on all the bolts in that joint.

Half-dry, half-oily bolts makes for insanely unequal clamping force, far inferior than an evenly-weak joint. And remember what you did! Your next mechanic’ll tighten it too much if he follows your oil-on-studs procedure but torques to a spec assuming they’re dry.

Don’t mix with thread locking adhesives. These act as a lubricant when wet and will harden.

Don’t mix with stainless fasteners. Use the stainless table. There is also one for them, which has its own lubricated column.

Don’t mix with structural A325/A490 assemblies. Instead, there’s a pre-installation check to control lubrication state. For metric lubricated values (mu = 0.10), see our metric bolt torque chart.

This table will help determine the proper torque for imperial austenitic stainless screws. Specificly it applies to 18-8 alloys including the 302, 303 and 304 stainless alloys. It also includes 316 stainless steel appropriate for chemical environments and salt water (marine).

First identify the thread size. Next look at the column labeled either dry or lubricated for what alloy you are using. Finally, verify whether the number represent an inch-pound or foot-pound value in the unit column.

Inch-pounds are used for machine screw gauges up to 7/16 inches. Foot-pounds is used for gauge sizes 1/2 inch and larger. Many people makes the mistake of confusing these units. Over torquing occurs when you mix them together, typically the number is multiplied by 12.

The numbers aren't derived using some kind of proof load formula. These are maximum recommended values based off tests conducted by Fastenal lab. They tested clean, dry, or nearly dry fastener in the lab. Other sites such as Engineers Edge has comparable data for dry conditions.

A proof load is not specified for stainless steel as it is for J429 grades. Hex bolts that are commonly called 18-8 are rated lower then Grade 5 bolts. Never use a stainless bolt where you need Grade 5 or Grade 8 torque.

The biggest danger with stainless steel is galling, also known as cold welding. Under thread pressure, the metal seize. This causes the fastener to twist off before reaching its table value or lock solid, longer rundowns make galling worse. Impact drivers further make galling worse.

Dry assembly and prevailing-torque lock nuts is an issue too. If at all possible, use the lubricated column. Moly or graphite anti-seize will help prevent seizure. Always run the nut down slowly by hand and stop instantly if it suddenly gets rough.

The 316 alloy is a little stronger at this point. Your selection decision should of been based on the corrosiveness of the environment you are using them in. Don’t make your choice by torque value.

Not all sizes are tested and published by lab. For instance, there isn’t data given for 1-3/8 inches. Follow the data sheet from the fastener manufacturer if it’s one of these size. Don’t extrapolate this table for missing sizes.

For metric stainless, however, it’s another story. Metric stainless are broken down into classes: A2-70 and A4-70. This is based on a different type of friction. Those numbers appear in the metric bolt torque chart.

Ultimately, it all goes back to the equipment manufacturer’s documentation. Follow their instructions for each table on this page.

The above table summarizes the structural bolts that were commonly found in connection assemblies of bridges and steel buildings. Specifically it includes A325 (Group 120) and A490 (Group 150). Since 2015 these are all covered under ASTM F3125.

Pretension columns indicates the minimum installed tension from Table 5.2 of the RCSC Specification. By definition this is 70% of the minimum tensile strength of the bolt.

Torque columns is estimated values only. These are calculated based off minimum pretension at K = 0.20 with a plain assembly (no lubricant) and match the published chart by Portland Bolt.

Read the distinction closely. In pretensioned and slip-critical joints, the specification controls tension, not torque.

Accepted installations are direct tension indicating washers, turn-of-nut, twist-off tension-control bolts, calibrated wrench, and the combined method. Use the torque column in this table for ballpark an inspection wrench setting or sizing tools. Not for installing bolts; it can be used to sanity check your calibration.

Not every structural connection need pretension. Pulling those plies together snugly, so they are firmly in contact, will often suffice. That usually means using the maximum force of someone with an ordinary spud wrench.

Pretension everything? No. Always refer to the drawings first. It is a complicated inspection, a waste of labour, and unnecessary pretension.

But then there’s coating. The assembly has much higher and more uneven friction when hot-dip galvanized. Torque-wise, its lubricating wax reduce the necessary torque by roughly half, to about K = 0.10. Galvanized A325 nuts need this wax.

So that’s why rotational-capacity awareness on galvanized assemblies is a requirement of F3125. And that’s why RCSC Section 7 contain a pre-installation verification test. Each lot, as delivered, has to shows that it will reach or exceed 1.05 times the required pretension.

Galvanizing is prohibited with A490 due to hydrogen embrittlement. Once completely tensioned, neither grade may be reused.

No pretension is required on A307 machine bolts, and no proof load is published; they are simply snug tight. When an A307 demands that you provide some number instead of torque, consider that as a loose approximation of the Grade 2 column from the coarse table.

The metric structural matches follow the EN 14399 practice, which isn’t in this chart.

When your machine mixes unit systems and you need the right torque value, this is the small table you use. The row you compare with is the one marked by whatever appears on your bolt head. Next you consult the imperial tables above for SAE grade. And the separate metric bolt torque chart for property class (which are in that fifth column).

These are the industry-wide approximations of strength for the pairs. Class 8.8 matches grade 5 since they’re approximately equal with tensile strengths around 830 MPa or 120,000 psi. Next up, class 10.9 equals grade 8. They are roughly equal with 1040 MPa or 150,000 psi tensile strength. You find grade 2 between 5.8 and 4.8. The structural pair equates A325 to class 8.8 assemblies. And it equates A490 to class 10.9 assemblies. Fastenal and Wilson-Garner also publish these correspondences.

The ranges in the metric column reflect ISO 898-1 size breaks. For instance, class 8.8 is 580 MPa proof and 800 MPa tensile for M16 or smaller. After that it’s 600 and 830 respectively.

Grade 2 and Grade 5 change proof stress at 3/4 in and 1 in, just like metric classes do. The way the heads are marked is different than too, but not just in quantity. Radial dashes indicate SAE and the grade number equates to dashes plus two. With metric classes they simply stamp the class numbers on the head itself.

The threads themselves are never equivalent. An M12x1.75 nut starts a 1/2-13 UNC bolt. Then it strips it. The diameters isn't the same and equivalence doesn't ever extend to torque values either.

For example, a Grade 5 1/2 in bolt is 75 ft-lb dry. On the same basis, its closest metric cousin would be M12 class 8.8 which is around 65 ft-lb. You ALWAYS torque from the table that corresponds to the actual thread you have in your hand.