Torque Conversion

Torque Conversion Formulas

Torque is a standard term that is comprised of “distance and force”. Since the force is applied to a threaded component in a circular motion, the distance applies to the radius (center of the torque wrench drive to a designated point on the torque wrench handle). In the case of wire harness applications, it is usually expressed in INCH-POUNDS, NEWTON-METERS, or KILOGRAM-CENTIMETERS. When extensions such as a crowfoot, or strap wrench is added to a torque wrench, it changes the distance (radius), so a mathematical formula is used to determine the correct torque readings on the torque wrench to compensate for the added length. We have included the following formulas for your convenience.

A = (Length) Distance from center of torque wrench square drive to center of the puller’s hand grip.

B = Distance from center of torque wrench square drive to center of drive at end of extension.

C = (Torque) Torque wrench setting.

D = Torque desired at drive on end of extension.

P = (Force) Pull applied.

To determine torque wrench setting:   C = (D*A) / (A+B)

NOTE: After computing “C” and setting wrench to computation, measure and mark “A” where pull is applied.

It is recommended that the axis of the extension always be used in line with axis of the torque wrench as shown above.

Should it be necessary, due to obstructions, to have an angle between the two axes, then the above formula is modified as follows. Due to increasing rounding errors, keep the angle as small as possible.

A, B, C, D, & P are the same as above.

E = Effective moment arm of the extension.

Ø = Angle between extension axis and torque wrench axis.

E = (B)(COS Ø)

Therefore:

C = (D*A) / (A+(B*COS Ø))

When Ø = 0, COS Ø = 1, then equation is reduced to C = (D*A) / (A+B)

When Ø = 90°, COS Ø = 0 then C = D (Regardless of the length B)

 

TORQUE CONVERSION CHARTS

These torque conversion charts were calculated for the BT-ST-301D Digital Torque Tool. If any other torque tool or instrument is used, calculate the torque conversion by using the mathematical formula above.

TORQUE CONVERSION CHART

FOR BT-BS-611 and BT-BS-618 SERIES  USED WITH BT-ST-301D
Diameter of
Part Being
Tightened
DESIRED TORQUE VALUE (in-lbs) (“D”)
40
60
80
100
120
140
160
180
200
1.00″
 31 46 61 76 92 107 122 137 153
1.50″
 30 45 59 74 89 104 119 134 148
1.75″
 29 44 59 73 88 103 117 132 147
2.00″
 29 43 58 72 87 101 116 130 145
2.25″
 29 43 57 71 86 100 114 129 143
2.50″
 28 42 56 70 85 99 113 127 141
2.75″
 28 42 56 70 84 97 111 125 139
3.00″
 28 41 55 69 83 96 110 124 138
3.25″
 27 41 54 68 82 95 109 122 136
3.50″
 27 40 54 67 81 94 107 121 134
3.75″
 27 40 53 66 80 93 106 119 133
4.00″
 26 39 52 66 79 92 105 118 131
TORQUE READING ON INSTRUMENT (“C”)

 

TORQUE CONVERSION CHART

FOR BT-BS-609 SERIES USED WITH BT-ST-301D
Diameter of
Part Being
Tightened
DESIRED TORQUE VALUE (in-lbs) (“D”)
40
60
80
100
120
140
160
180
200
0.50″
 34 50 67 84 101 118 135 151 168
0.75″
 33 50 66 83 99 116 133 149 166
1.00″
 33 49 65 82 98 114 131 147 163
1.50″
 32 48 64 79 95 111 127 143 159
1.75″
 31 47 63 78 94 110 125 141 157
2.00″
 31 46 62 77 93 108 124 139 155
2.25″
 31 46 61 76 92 107 122 137 153
2.50″
 30 45 60 75 90 105 121 136 151
TORQUE READING ON INSTRUMENT (“C”)

 

TORQUE CONVERSION CHART

FOR BT-BS-610 SERIES USED WITH BT-ST-301D
Diameter of
Part Being
Tightened
DESIRED TORQUE VALUE (in-lbs) (“D”)
40
60
80
100
120
140
160
180
200
0.25″
 36 54 72 89 107 125 143 161 179
0.50″
 35 52 70 87 104 122 139 156 174
0.75″
 34 51 68 86 103 120 137 154 171
1.00″
 34 51 67 84 101 118 135 152 169
1.50″
 33 49 65 81 98 114 130 146 163
TORQUE READING ON INSTRUMENT (“C”)

FOR OUR OLDER TORQUE WRENCHES

TORQUE CONVERSION CHART

For BT-BS-609 and 610 Series used with BT-ST-751 & BT-ST-701 (older models)
Diameter of
Part Being
Tightened
DESIRED TORQUE VALUE (in-lbs) (“D”)
40 60 80 100 120 140 160 180 200
.50 36 53 70 88 105 – – – –
.75 35 52 69 87 104 122 – – –
1.00 34 51 68 85 102 120 135 – –
1.50 33 50 67 83 100 117 133 150 –
1.75 33 49 66 82 99 115 132 148 164
2.00 33 49 65 81 97 114 130 146 162
2.25 32 48 65 80 96 112 128 144 160
2.50 32 48 62 79 95 111 127 143 158
TORQUE READING ON INSTRUMENT (“C”)

 

TORQUE CONVERSION CHART

For BT-BS-611 and 618 Series used with BT-ST-751 & BT-ST-701 (older models)
Diameter of
Part Being
Tightened
DESIRED TORQUE VALUE (in-lbs) (“D”)
40 60 80 100 120 140 160 180 200
.50 33 49 65 82 99 – – – –
.75 32 48 64 81 97 113 – – –
1.00 32 48 64 80 96 112 128 – –
1.50 31 47 62 78 93 109 125 140 –
1.75 31 46 62 77 92 108 123 139 154
2.00 30 46 61 76 91 107 122 137 152
2.25 30 45 60 75 90 105 120 135 150
2.50 30 45 59 74 89 104 119 134 149
2.75 29 44 59 74 88 103 118 132 147
3.00 29 44 58 73 87 102 116 131 145
3.25 29 43 58 72 86 101 115 129 143
3.50 28 43 57 71 85 100 114 128 142
3.75 28 42 56 70 84 99 113 127 140
4.00 28 42 56 70 84 98 111 125 139
TORQUE READING ON INSTRUMENT (“C”)

THESE FACTORS ARE CALCULATED USING A MATHEMATICAL FORMULA.  SEVERAL VARIABLES INFLUENCE THE ACTUAL VALUE AND THE FACTORS ARE PUBLISHED AS A GUIDE ONLY.
© CRiMP-TECH AUSTRALIA PTY LTD