Screw Torque Reference


Grade 2 Low Carbon Steel

Typical fasteners in this category: All pan and flat machine screws. Most SEMS screws.

  • Low Carbon Steel
  • Tensile strength = 74,000 psi min.
  • Proof load = 55,000 psi
  • Yield strength = 41,250 psi

PARAMETERS THAT WILL CAUSE THE TORQUE TO LOWER

  • Thin female thread (Press in style nut)
  • Extruded and tapped hole in thin sheet metal
  • Failure of the drive system to develop the recommended torque
  • Tapped hole in soft material (die casting)
  • Insert in plastic
  • Over spin of power screw driver
SizeStress Area Sq. InchesClamp Load PoundsDesign Range PoundsTorque Inch Pounds
2 – 56.00370152122 – 1831.6 – 2.3
4 – 40.00604249199 – 2993.4 – 4.8
6 – 32.00909375300 – 4506 – 10
8 – 32.01401578462 – 69312 – 16
10 – 32.01999825660 – 99020 – 27
1/4 – 20.0318213121050 – 157541 – 57
5/18 – 18.0524321621729 – 259484 – 117
3/8 – 16.0774931962557 – 3836150 – 207

GRADE 5 LOW CARBON STEEL

Typical fasteners in this category: Case hardened machine screws, some SEMS screws, thread forming screws.

  • Medium carbon steel
  • Tensile strength = 120,000 psi min.
  • Proof Load = 85,000 psi
  • Clamp load = 63,750 psi

PARAMETERS THAT WILL CAUSE THE TORQUE TO LOWER

  • Thin female thread (Press in style nut)
  • Extruded and tapped hole in thin sheet metal
  • Failure of the drive system to develop the recommended torque
  • Tapped hole in soft material (die casting)
  • Insert in plastic
  • Over spin of power screw driver
SizeStress Area Sq. InchesClamp Load PoundsDesign Range PoundsTorque Inch Pounds
4 – 40.00604385308 – 4625 – 7
6 – 32.00909580464 – 69510 – 14
8 – 32.01401893714 – 107218 – 25
10 – 32.0199912741020 – 153030 – 42
1/4 – 20.0318220281622 – 243265 – 88
5/16 – 18.0524333422674 – 4011130 – 180
3/8 – 16.0774949403952 – 5928231 – 320

GRADE 8 LOW CARBON STEEL

Typical fasteners in this category: Socket head cap screws, through heat treated torx screws.

  • Alloy steel
  • Tensile strength = 150,000 psi min.
  • Proof Load = 120,000 psi
  • Clamp load = 90,000 psi

PARAMETERS THAT WILL CAUSE THE TORQUE TO LOWER

  • Thin female thread (Press in style nut)
  • Extruded and tapped hole in thin sheet metal
  • Failure of the drive system to develop the recommended torque
  • Tapped hole in soft material (die casting)
  • Insert in plastic
  • Over spin of power screw driver
SizeStress Area Sq. InchesClamp Load PoundsDesign Range PoundsTorque Inch Pounds
4 – 40.00604543435 – 6498 -11
6 – 32.00909818654 – 98215 – 20
8 – 32.0140112601009 – 151330 – 37
10 – 32.0199917991439 – 215844 – 62
1/4 – 20.0318228642291 – 343793 – 129
5/16 – 18.0524347183775 – 5662199 – 265
3/8 – 16.0774969745579 – 8369339 – 471

Optimum hole size may vary depending on material joined. Pencom recommends testing in the specific application to determine actual hole size and tightening requirements. Contact an account representative for samples.

METRIC CLASS 4.8

Typical fasteners in this category: All pan and flat machine screws. Most SEMS screws.

  • Low Carbon Steel
  • Tensile strength = 420 MPa (60,900 psi min.)
  • Yield strength = 310 MPa (44,950 psi)

PARAMETERS THAT WILL CAUSE THE TORQUE TO LOWER

  • Thin female thread (Press in style nut)
  • Extruded and tapped hole in thin sheet metal
  • Failure of the drive system to develop the recommended torque
  • Tapped hole in soft material (die casting)
  • Insert in plastic
  • Over spin of power screw driver
SizeStress Area Sq. InchesClamp Load PoundsDesign Range PoundsTorque Inch Pounds
M1.6 x 0.35.001975443 – 60.53 – .73
M2 x 0.4.003219072 – 991.1 – 1.5
M2.5 x 0.45.00525150120 – 1652.2 – 3.1
M3 x 0.5.00780230184 – 2533.9 – 5.4
M3.5 x 0.6.01051306245 – 3376.0 – 8.3
M4 x 0.7.01361396317 – 4369.0 – 12
M5 x 0.8.02201647517 – 71218 – 24
M6 x 1.0.03116913730 – 100530 – 41
Filed under: Technical Bulletins