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Extension Spring Normal Load Tolerances load / force Specifications

Spring Engineering and Design

Extension Spring Normal Load Tolerances load / force Specifications

Most extension springs are specified with initial tension, which is an internal force that holds the coils tightly together. Unlike a compression spring, which has zero load at zero deflection, an extension spring can have a preload at zero deflection.

The two most common loops or hooks for extension springs are the twist loop and the cross loop. These loops are made with standard looping tools and so should be specified whenever possible to minimize cost. If required by the application, many special types of extension-spring loops are offered by the spring industry at additional cost.

Extension Spring Normal Load Tolerances load / force Specifications

Where:

D = Mean coil diameter (in)
d = Wire diameter (in)

Normal (typical) Load Tolerances for Extension Springs, ± Percent of Load

Normal Load Tolerances for Extension Springs, Percent of Load

Index
D/d
Free length
deflection
L/F
Wire diameter, in
0.015
0.022
0.032
0.044
0.062
0.092
0.125
0.187
0.250
0.375
0.437
4
12
20.0
18.5
17.6
16.9
16.2
15.5
15.0
14.3
1 3.8
13.0
12.6
8
18.5
17.5
16.7
15.8
15.0
14.5
14.0
13.2
12 .5
11.5
11.0
6
16.8
16.1
15.5
14.7
13.8
13.2
12.7
11.8
11 .2
9.9
9.4
4.5
15.0
14.7
14.1
13.5
12.6
12.0
11.5
10.3
9.7
8.4
7.9
2.5
13.1
12.4
12.1
11.8
10.6
10.0
9.1
8.5
8. 0
6.8
6.2
1.5
10.2
9.9
9.3
8.9
8.0
7.5
7.0
6.5
6.1
5.3
4.8
0.5
6.2
5.4
4.8
4.6
4.3
4.1
4.0
3.8
3.6
3 .3
3.2
6
12
17.0
15.5
14.6
14.1
13.5
13.1
12.7
12.0
11.5
11.2
10.7
8
16.2
14.7
13.9
13.4
12.6
12.2
11.7
11.0
10 .5
10.0
9.5
6
15.2
14.0
12.9
12.3
11.6
10.9
10.7
10.0
9. 4
8.8
8.3
4.5
13.7
12.4
11.5
11.0
10.5
10.0
9.6
9.0
8 .3
7.6
7.1
2.5
11.9
10.8
10.2
9.8
9.4
9.0
8.5
7.9
7.2
6.2
6.0
1.5
9.9
9.0
8.3
7.7
7.3
7.0
6.7
6.4
6.0
4 .9
4.7
0.5
6.3
5.5
4.9
4.7
4.5
4.3
4.1
4.0
3.7
3 .5
3.4
12
15.8
14.3
13.1
13.0
12.1
12.0
11.5
10.8
10.2
10.0
9.5
8
15.0
13.7
12.5
12.1
11.4
11.0
10.6
10.1
9. 4
9.0
8.6
6
14.2
13.0
11.7
11.2
10.6
10.0
9.7
9.3
8.6
8.1
7.6
8
4.5
12.8
11.7
10.7
10.1
9.7
9.0
8.7
8.3
7.8
7.2
6.6
2.5
11.2
10.2
9.5
8.8
8.3
7.9
7.7
7.4
6.9
6.1
5.6
1.5
9.5
8.6
7.8
7.1
6.9
6.7
6.5
6.2
5.8
4 .9
4.5
0.5
6.3
5.6
5.0
4.8
4.5
4.4
4.2
4.1
3.9
3 .6
3.5
12
14.8
13.3
12.0
11.9
11.1
10.9
10.5
9.9
9. 3
9.2
8.8
8
14.2
12.8
11.6
11.2
10.5
10.2
9.7
9.2
8.6
8.3
8.0
6
13.4
12.1
10.8
10.5
9.8
9.3
8.9
8.6
8.0
7.6
7.2
10
4.5
12.3
10.8
10.0
9.5
9.0
8.5
8.1
7.8
7.3
6.8
6.4
2.5
10.8
9.6
9.0
8.4
8.0
7.7
7.3
7.0
6.5
5.9
5.5
1.5
9.2
8.3
7.5
6.9
6.7
6.5
6.3
6.0
5.6
5 .0
4.6
0.5
6.4
5.7
5.1
4.9
4.7
4.5
4.3
4.2
4.0
3 .8
3.7
12
14.0
12.3
11.1
10.8
10.1
9.8
9.5
9.0
8.5
8.2
7.9
8
13.2
11.8
10.7
10.2
9.6
9.3
8.9
8.4
7.9
7.5
7.2
6
12.6
11.2
10.2
9.7
9.0
8.5
8.2
7.9
7.4
6.9
6.4
12
4.5
11.7
10.2
9.4
9.0
8.4
8.0
7.6
7.2
6.8
6.3
5.8
2.5
10.5
9.2
8.5
8.0
7.8
7.4
7.0
6.6
6.1
5.6
5.2
1.5
8.9
8.0
7.2
6.8
6.5
6.3
6.1
5.7
5.4
4 .8
4.5
0.5
6.5
5.8
5.3
5.1
4.9
4.7
4.5
4.3
4.2
4 .0
3.3
12
13.1
11.3
10.2
9.7
9.1
8.8
8.4
8.1
7.6
7.2
7.0
8
12.4
10.9
9.8
9.2
8.7
8.3
8.0
7.6
7.2
6 .8
6.4
6
11.8
10.4
9.3
8.8
8.3
7.7
7.5
7.2
6.8
6 .3
5.9
14
4.5
11.1
9.7
8.7
8.2
7.8
7.2
7.0
6.7
6.3
5.8
5.4
2.5
10.1
8.8
8.1
7.6
7.1
6.7
6.5
6.2
5.7
5.2
5.0
1.5
8.6
7.7
7.0
6.7
6.3
6.0
5.8
5.5
5.2
4.7
4.5
0.5
6.6
5.9
5.4
5.2
5.0
4.8
4.6
4.4
4.3
4 .2
4.0
12
12.3
10.3
9.2
8.6
8.1
7.7
7.4
7.2
6.8
6.3
6.1
8
11.7
10.0
8.9
8.3
7.8
7.4
7.2
6.8
6.5
6 .0
5.7
6
11.0
9.6
8.5
8.0
7.5
7.1
6.9
6.5
6.2
5. 7
5.4
16
4.5
10.5
9.1
8.1
7.5
7.2
6.8
6.5
6.2
5.8
5.3
5.1
2.5
9.7
8.4
7.6
7.0
6.7
6.3
6.1
5.7
5.4
4 .9
4.7
1.5
8.3
7.4
6.6
6.2
6.0
5.8
5.6
5.3
5.1
4 .6
4.4
0.5
6.7
5.9
5.5
5.3
5.1
5.0
4.8
4.6
4.5
4 .3
4.1
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