17-1. Compression coil spring
17-1.Compression coil spring
Symbol description and unit
Spring deflection：[mm]
δ=8*n*D
3
*F/(G*d
4
)
δ=
Spring constant： [kgf/mm]
k=G*d
4
/(8*n*D
3
)
k=
Spring index：
C=D/d
C=
Whirl stress correction factor：
κ=(4*C-1)/(4*C-4)+0.615/C
κ=
Maximum shear stress： [Kgf/mm
2
]
τ=8*κ*D*F/(π*d
3
)
τ=
Free length： [mm]
H=H2+δ
H=
Adhesion length： [mm]
H1=n*d+1.5*d
H1=
n: Effective number of turns
D：Average coil diameter [mm]
F： Load on the spring [kgf]
G： Lateral modulus [kgf/mm
2
]
d： Material diameter [mm]
H2： Mounting length [mm]
Piano wire（SWPA、SWPB） Standard diameter (JIS G 3522)
0.08 0.09 0.10 0.12 0.14 0.16 0.18 0.20 0.23 0.26 0.29 0.32 0.35 0.40 0.45 0.50 0.55 0.60 0.70 0.80 0.90 1.00 1.20 1.40 1.60 1.80 2.00 2.30 2.60 2.90 3.00 3.20 3.50 4.00 4.50 5.00 5.50 6.00 6.50 7.00 8.00 9.00 10.0
Lateral modulus G The value of the(Kgf/mm
2
)
Piano wire（SWPA,SWPB） 8000
Spring steel(SUP) 8000
Oil temper wire(SWO) 8000
Stainless steel wire(SUS-WH)
7000〜7500
Stainless steel wire for springs(SUS-WP)
7000〜7500
1Kg=9.8N
References: "Machine Official Collection" (co-authored by Masaaki Oishi / Tatsuo Inami) Mechanical Design Spring, page 98, refer to compression coil springs.