INTRODUCTION 19
Table 1.2 Coefficients and Exponents for Eq. 1.16
ASTM# Material Range of d Exponentb Coefficient A Correlation
(mm) (MPa) Factor
A227 Cold drawn 0.5-16 – 0.1822 1753.3 0.998
A228 Music wire 0.3-6 – 0.1625 2153.5 0.9997
A229 Oil tempered 0.5-16 – 0.1833 1831.2 0.999
Step 8: The four types of end conditions for the coil, as shown in Figure 1.5, are
Plain-Ends ⇒ Na = Nt (total number of coils)
Plain-Ground-ends ⇒ Na = Nt – 1
Figure 1.5 End conditions for a helical compression spring
A229
A227
A228
(A) Plain end (B) Plain and ground end (C) Square end
SI (mm)
0.10
0.12
0.16
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
0.60
0.65
0.70
0.80
0.90
1.00
1.10
1.20
1.40
1.60
1.80
2.00
2.20
2.50
2.80
3.00
3.50
4.00
4.50
5.00
5.50
6.00
6.50
7.00
8.00
9.00
10.0
11.0
12.0
13.0
14.0
15.0
16.0
Table 1.1(b) Preferred wire diameters