Enter the material constant, the nominal bolt diameter (ft), lubrication factor, and the axial bolt force (lbf) into the calculator to determine the Screw Torque.
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Screw Torque Formula
The following formula is used to calculate the Screw Torque.
Ts = K*F*d * (1-L / 100)
- Where Ts is the Screw Torque (lb-ft)
- K is the material constant
- .2 for normal steel bolts from .250″ to 1″
- d is the nominal bolt diameter (ft)
- F is the axial bolt force (lbf)
- L is the force lost due to lubrication (%)
How to Calculate Screw Torque?
The following example problems outline how to calculate Screw Torque.
Example Problem #1
- First, determine the material constant. In this example, the material constant is determined to be .2 .
- Next, determine the nominal bolt diameter (ft). For this problem, the nominal bolt diameter (ft) is measured to be .25.
- Next, determine the axial bolt force (lbf). In this case, the axial bolt force (lbf) is found to be 1000.
- Next, determine the loss due to lubrication. In this example, this is 50%.
- Finally, calculate the Screw Torque using the formula above:
Inserting the values from above and solving yields:
Ts = K*F*d * (1-L / 100) = (lb-ft)
Ts = .2*1000*.25 * (1-50 / 100) = 25 lb-ft
Example Problem #2
Using the same method as above, determine the variables required by the formula. For this example problem, these are:
material constant = .2
nominal bolt diameter (ft) = .3
axial bolt force (lbf) = 5000
lubrication loss (%) = 35
Enter these given values into the calculator or above yields:
Ts = .2*5000*.3 * (1-35 / 100) = 195 (lb-ft)