Safety Instruction Manual

CEMA STANDARD NO: 352-2012
CHART A - BOLT TORQUE GUIDE
Formula: T= K x D x P
• T Target tighten torque (the result of this formula is in inch pounds, dividing
by 12 yields foot pounds)
• K Coefficient of friction (nut factor), always an estimation in this formula
• D Bolts nominal diameter in inches
• P Bolt's desired tensile load in pounds (generally 75% of yield strength)
[P(lbs) = (75%) Yield Strength * Tensile Stress Area]
Bolt Torque Guide is for fasteners used to assemble screw conveyors and does not include coupling bolts. Over
tightening of coupling bolts could result in failure in tension.
CEMA recommends tightening coupling bolts to 75-percent of the values given in the Bolt Torque Guide to
eliminate over tightening of coupling bolts
END OF DOCUMENT
15.
All bolted applications should be evaluated to determine optimum tightening torque.
K factor in the formula below is considered an estimate.
The most commonly used K factor is 0.20 for plain finished bolts.
Bolt Dia. (inches)
Threads Per Inch
(UNC)
SAE 2SAE 5SAE 8
18-8 & 316
Stainless Steel
1/4 20 59126
5/16 18 11 18 25 11
3/8 16 18 31 44 20
7/16 14 28 49 69 29
1/2 13 44 73 105 40
9/16 12 63 108 149 52
5/8 11 96 147 212 86
3/4 10 158 252 351 115
7/8 9 219 389 552 180
18316 589 784 240
GENERAL BOLT TIGHTENING TORQUE (Ft. lbs.)