# Fastener Tightening Torque Information

## Adjustment of Torque for Tightening method and Friction Coefficient

Two major points have to be accounted for when installing a fastener.

• 1. Inaccuracy of torque wrench tightening method can range anywhere from ±17 to ±23%
• 2. The friction coefficient changes when using lubrication on the thread.

### 1. Inaccuracy of tightening method

A torque wrench has a “scatter” (tolerance) of ±17% to ±23%. We must account for this in order not to over-tighten the fastener.

 Example: A M30-12.9 fastener has a maximum tightening torque of 2,280 Nm, based on a friction coefficient of 0.125 (zinc plated)Maximum torque: 2,280Nm (= 123%) (or 117%)Mean torque if scatter is +23% = 2,280 / 1.23 = 1,854 NmMinimum torque if scatter is +23% = 1,854 x 0.77 = 1,428 NmTorque should be set to 1,854 Nm (mean torque) on the torque wrench

The accuracy of the tightening method needs to be accounted for, in order to not over-tighten the fastener.

### 2. Friction coefficient

The surface condition of a fastener may change the torque that can be applied and needs to be accounted for.

Friction coefficients for standard finish fasteners

Surface ConditionLubrication Condition
ScrewNutOiledMoS2-Paste
- no treatment - phosphate- no treatment0.12-0.180.05-0.10
- electroplated appx. 8 μm- electroplated appx. 5 μm0.12-0.18
- dacromet-coated 6-8 μm- dacromet-coated 6-8 μm0.10-0.14
 Example: A M30-12.9 fastener using MoS2 paste.A M30-12.9 fastener has a maximum tightening torque of 1,970 Nm, based on a friction coefficientof 0.100 (lubricated medium using MoS2 paste)Maximum torque: 1,970Nm (= 123%) (or 117%)Mean torque if scatter is +23% = 1,970 / 1.23 = 1,602 NmMinimum torque if scatter is +23% = 1,602 x 0.77 = 1,234 NmTorque should be set to 1,602 Nm (mean torque)on the torque wrench

The accuracy of the tightening method, as well as the change in friction, needs to be accounted for in order not to over-tighten the fastener.

#### General Torque Figures

A torque value will be influenced by the fastening methods and tools used. The only way to determine an exact torque value is by actual application. The following figures are general guidelines only.

Figures in ft. lbs.

8.810.912.9
M30.801.11.3
M41.82.63.1
M53.65.16.2
M671012
M8172529
M10334858
M126085102
M1497137165
M16150208250
M18201287342
M20282398479
M22390552664
M24499750843
M2774610511266
M3098213831657
M33133118752250
M36171724072895
M39222031203750
M42273738404638
M45339047625722
M48409557756825
M52525073879000
M566547922511280
M6081751147513800
M6499001395017175
M68120001695020100
M72142502010024000
M76168002362528350
M80197252760033375
M85240003322540125
M90283503892547700
M95334504687556250
M100390005475066000

#### Torque - Metric Fasteners

Diameter

Recommended Seating Torque (NM)Proof Torque min. (NM)
ISO 4762

DIN 912

DIN 7984ISO 10642

DIN 7991

ISO 7380ISO 7379ISO 4014/ 4017

DIN 931 / DIN 933

ISO 4162ISO

4026 / 4027 4028 / 4029

Socket Cap

Screws

Socket Cap

Screws

Countersunk

Socket Cap

Screws

Socket Cap

Screws

Socket

Shoulder

Screws

Cap Screws

Hexagon Flange

Screws

Socket Set

Screws

10.912.910.910.912.910.912.912.910.912.910.912.945H
M1.60.250.30
M20.500.63
M2.51.031.27
M31.832.201.151.151.351.151.350.90
M44.274.832.702.703.102.703.102.50
M58.6410.05.405.406.105.406.108.6410.08.6410.05.00
M614.716.89.159.1510.59.1510.55.614.716.814.716.88.50
M6.55.6
M835.641.022.022.026.022.026.09.635.641.035.641.020.0
M1070.681.044.044.052.044.052.02570.681.070.681.040.0
M1212314277.077.090.077.090.05112314212314265.0
M1351
M1419522612212214319522619522665.0
M1630535019019022519022592305350305350160
M18420485262420485310
M20596685371370440245596685310
M22811930811930
M241031118010311180
M25485
M271508173015081730
M302048238020482380
M3327873262
M3635804190
M3946335420

#### Torque - Imperial Fasteners

Diameter

Recommended Seating Torque (in-lb)Proof Torque min. (in-lb)
ASME B18.3ASME B18.2.1IFI-111ASME B18.3
Socket Cap

Screws

Socket Cap

Screws

Countersunk

Socket Cap

Screws

Socket Cap

Screws

Socket

Shoulder

Screws

Cap Screws

SAE J429

Hexagon Flange

Screws

SAE J429

Socket Set

Screws

#02.261.421.421.1
#14.012.522.522.1
#26.654.184.182.1
#310.16.336.336.0
#414.18.888.888.886.0
#520.813.113.113.111
#626.216.516.516.511
#848.030.130.130.123
#1069.543.743.743.740
1/41661041041043513413494
5/1634221521521590277277183
3/8608382382382200491491317
7/16973611611785785502
1/2148493193193136312021202750
9/1617321732
5/82792172217221722922238623861460
3/4495230541864422542252520
7/87991492868235750
11197973883443102268000
1-1/8169681046414485
1-1/42394414766563720442
1-3/8313941936026806
1-1/241611256921200235573

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