Extension Spring Calculator

	Customer input field
	Explanation display field
Blank	Display after calculation

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the optimal design

Tokai Spring industries, Inc.

STEP1. Enter the required dimensions in the yellow cells

Dimension input field
Material
Wire diameter d		mm
Coil mean diameter D		mm
Active coils N		Coils
Free length H (Auto calculated if blank)		mm
Spring constant (Calculated automatically)		N/mm

*The initial tension is calculated as 0 N.

*The calculable free length is up to 700 mm.
Please consult us if it exceeds 700 mm.

*If you need a length longer than the free length in the calculation,
widen the pitches or lengthen the hooks.

Reverse calculation result
Required spring constant		N/mm
Reverse calculation wire diameter		mm
Reverse calculation center diameter		mm
Reverse calculation active coils		Coils

STEP2. Enter the required twist angle in the yellow cells

Load/Static stress characteristics field
	Load P(N) input	Spring usage range		Coil shear stress(N/mm²)		Tensile stress of hook
	Load P(N) input	Height(mm)	Deflection(mm)	τ	τ₀	σ	Pass/fail
First load
Second load
Third load
Fourth load
Free state	－		－	－	－	－	－

Please check the calculation result.

Fixed basic specifications
Outer diameter	mm	Bend radius	mm	Coil part maximum stress		N/mm²
Inner diameter	mm	Coil part solid height	mm	Hook part maximum stress		N/mm²
D/d	－	Hook length on one side	mm	－	－	－

Design advice on calculation result.

Advice on shape	Active coils N
	Active coils N
	D/d
Advice on stress	Coil shear stressτ₀ (First load)
	Coil shear stressτ₀ (Second load)
	Coil shear stressτ₀ (Third load)
	Coil shear stressτ₀ (Fourth load)
	Tensile stress of hook (First load)
	Tensile stress of hook (Second load)
	Tensile stress of hook (Third load)
	Tensile stress of hook (Fourth load)

This comment is for reference only. Even if a
correction message appears for the entered value,
we may still be able to create an optimized design
for you. Feel free to contact us by pressing the
'Contact Us' button.