Helical extension springs exert a force by pulling or stretching them. Usually, they are made from round wire and are close-wound with the initial tension between the coils. Their ends can be formed with loops in many varieties to attach to their applications.
Material data sheet:
Common Spring Materials |
Max |
|
St |
Sb |
|
Music Wire |
45 |
75 |
Chrome Silicon |
45 |
75 |
Chrome Vanadium |
45 |
75 |
302 Stainless Steel |
35 |
55 |
316 Stainless Steel |
35 |
55 |
17-7 Stainless Steel |
45 |
75 |
The following tables give tolerances that can be used as a reference. Actual manufacturing tolerances will depend on the spring specifics.
Outside Diameter Tolerances:
Wire |
Spring Index, D/d |
||||||
4 |
6 |
8 10 12 |
14 |
16 |
|||
0.015 |
0.002 | 0.002 | 0.003 | 0.004 | 0.005 | 0.006 | 0.007 |
0.023 |
0.002 | 0.003 | 0.004 | 0.006 | 0.007 | 0.008 |
0.01 |
0.035 |
0.002 | 0.004 | 0.006 | 0.007 | 0.009 | 0.011 | 0.013 |
0.051 |
0.003 | 0.005 | 0.007 |
0.01 |
0.012 | 0.015 | 0.017 |
0.076 |
0.004 | 0.007 |
0.01 |
0.013 | 0.016 | 0.019 | 0.022 |
0.114 |
0.006 | 0.009 | 0.013 | 0.018 | 0.021 | 0.025 | 0.029 |
0.171 |
0.008 | 0.012 | 0.017 | 0.023 | 0.028 | 0.033 | 0.038 |
0.25 |
0.011 | 0.015 | 0.021 | 0.028 | 0.035 | 0.042 | 0.049 |
0.375 |
0.016 |
0.02 |
0.026 | 0.037 | 0.046 | 0.054 | 0.064 |
0.5 |
0.021 |
0.03 |
0.04 |
0.062 |
0.08 |
0.1 |
0.125 |
Spring Free Length Tolerances |
|
.5 in or less |
0.02 |
0.5″ to 1.0″ |
0.03 |
1″ to 2.0″ |
0.04 |
2″ to 4″ |
0.06 |
4″ to 8″ |
0.093 |
8″ to 16″ |
0.156 |
16″ to 24″ |
0.218 |