## Fastener 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 Nm Minimum torque if scatter is +23% = 1,854 x 0.77 = 1,428 Nm Torque 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 Condition Lubrication Condition
Screw Nut Oiled MoS2-Paste
- no treatment - phosphate - no treatment 0.12-0.18 0.05-0.10
- electroplated appx. 8 μm - electroplated appx. 5 μm 0.12-0.18
- dacromet-coated 6-8 μm - dacromet-coated 6-8 μm 0.10-0.14
 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 coefficient of 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 Nm Minimum torque if scatter is +23% = 1,602 x 0.77 = 1,234 Nm Torque 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.

8.8 10.9 12.9
M3 0.80 1.1 1.3
M4 1.8 2.6 3.1
M5 3.6 5.1 6.2
M6 7 10 12
M8 17 25 29
M10 33 48 58
M12 60 85 102
M14 97 137 165
M16 150 208 250
M18 201 287 342
M20 282 398 479
M22 390 552 664
M24 499 750 843
M27 746 1051 1266
M30 982 1383 1657
M33 1331 1875 2250
M36 1717 2407 2895
M39 2220 3120 3750
M42 2737 3840 4638
M45 3390 4762 5722
M48 4095 5775 6825
M52 5250 7387 9000
M56 6547 9225 11280
M60 8175 11475 13800
M64 9900 13950 17175
M68 12000 16950 20100
M72 14250 20100 24000
M76 16800 23625 28350
M80 19725 27600 33375
M85 24000 33225 40125
M90 28350 38925 47700
M95 33450 46875 56250
M100 39000 54750 66000

#### Torque - Metric Fasteners

Diameter
Recommended Seating Torque (NM) Proof Torque min. (NM)
ISO 4762
DIN 912
DIN 7984 ISO 10642
DIN 7991
ISO 7380 ISO 7379 ISO 4014/ 4017
DIN 931 / DIN 933
ISO 4162 ISO
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
10.9 12.9 10.9 10.9 12.9 10.9 12.9 12.9 10.9 12.9 10.9 12.9 45H
M1.6 0.25 0.30
M2 0.50 0.63
M2.5 1.03 1.27
M3 1.83 2.20 1.15 1.15 1.35 1.15 1.35 0.90
M4 4.27 4.83 2.70 2.70 3.10 2.70 3.10 2.50
M5 8.64 10.0 5.40 5.40 6.10 5.40 6.10 8.64 10.0 8.64 10.0 5.00
M6 14.7 16.8 9.15 9.15 10.5 9.15 10.5 5.6 14.7 16.8 14.7 16.8 8.50
M6.5 5.6
M8 35.6 41.0 22.0 22.0 26.0 22.0 26.0 9.6 35.6 41.0 35.6 41.0 20.0
M10 70.6 81.0 44.0 44.0 52.0 44.0 52.0 25 70.6 81.0 70.6 81.0 40.0
M12 123 142 77.0 77.0 90.0 77.0 90.0 51 123 142 123 142 65.0
M13 51
M14 195 226 122 122 143 195 226 195 226 65.0
M16 305 350 190 190 225 190 225 92 305 350 305 350 160
M18 420 485 262 420 485 310
M20 596 685 371 370 440 245 596 685 310
M22 811 930 811 930
M24 1031 1180 1031 1180
M25 485
M27 1508 1730 1508 1730
M30 2048 2380 2048 2380
M33 2787 3262
M36 3580 4190
M39 4633 5420

#### Torque - Imperial Fasteners

Diameter
Recommended Seating Torque (in-lb) Proof Torque min. (in-lb)
ASME B18.3 ASME B18.2.1 IFI-111 ASME 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
#0 2.26 1.42 1.42 1.1
#1 4.01 2.52 2.52 2.1
#2 6.65 4.18 4.18 2.1
#3 10.1 6.33 6.33 6.0
#4 14.1 8.88 8.88 8.88 6.0
#5 20.8 13.1 13.1 13.1 11
#6 26.2 16.5 16.5 16.5 11
#8 48.0 30.1 30.1 30.1 23
#10 69.5 43.7 43.7 43.7 40
1/4 166 104 104 104 35 134 134 94
5/16 342 215 215 215 90 277 277 183
3/8 608 382 382 382 200 491 491 317
7/16 973 611 611 785 785 502
1/2 1484 931 931 931 363 1202 1202 750
9/16 1732 1732
5/8 2792 1722 1722 1722 922 2386 2386 1460
3/4 4952 3054 1864 4225 4225 2520
7/8 7991 4928 6823 5750
1 11979 7388 3443 10226 8000
1-1/8 16968 10464 14485
1-1/4 23944 14766 5637 20442
1-3/8 31394 19360 26806
1-1/2 41611 25692 12002 35573