Bolt torque guide, Chart a - bolt torque guide – Martin Sprocket & Gear Screw Conveyor Safety User Manual
Page 19
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 2
SAE 5
SAE 8
18-8 & 316
Stainless Steel
1/4
20
5
9
12
6
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
1
8
316
589
784
240
GENERAL BOLT TIGHTENING TORQUE (Ft. lbs.)