Product Resources

Stock Constant Force Spring Selection Chart

Constant Force Balance Springs Sales Sheet

Pusher Variable Force Springs for POP Displays

Design Considerations for Constant Force Springs

There are many design factors that will affect the time and cost needed to manufacture your spring. Therefore, it’s important to work with a manufacturer like John Evans’ Sons that has the knowledge needed in the design phase.

  • Mounting Methods: There are several mounting methods. Your application will determine which mounting method is best for your spring’s design.
  • Material: The material selection is an important component of the design and project cost. The optimal spring material is often different in high temperature and corrosive environments. Material will certainly affect the design and project cost. High temperatures or corrosive environments will also affect the life of a spring and the required material.
  • Diameter and Load: Length, material width, thickness, and coil diameter affect the spring’s load. Increased loads can be obtained by using two or more constant force springs interwound, in tandem, or in other configurations.

All of these, plus other technical considerations, need to be discussed and specified prior to creating prototypes. Our design engineering team can help ensure calculations and configurations are exact in the design phase.

Our springs are most often used in the following industries and applications:

Constant Force Springs

Not sure if constant force springs can provide the right action for your product? Contact John Evans’ Sons for more information.

Spring Comparison Chart
for design parameter comparison (matl. thickness vs. cycle life vs. coiled dia.)

(material: T301 SS, Calculations shown are at 1.0” width, interpolate for other spring material widths)

Material Thickness2,500 cycles
10,000 cycles20,000 cycles75,000 cycles150,000 cycles
Coiled Dia.Load (lbs.)Coiled Dia.Load (lbs.)Coiled Dia.Load (lbs.)Coiled Dia.Load (lbs.)Coiled Dia.Load (lbs.)
0.0322.2620.52.65 15.53.3610.24.945.16.92.7
Constant force spring variables & formula.

Selection Charts for the Ideal Constant Force Spring

Selection Charts for the Ideal Constant Force Spring

Part NumberLoadMax Work DeflectionBand LengthFatigue Life (cycles)WidthFree I. D.Thickness
A 3X50-SL04D160.2312"16"20,0000.25"0.5160.004
A 3X50-SK04D15 0.3212"15"13,0000.25"0.4380.004
A 3X50-SL05E17 0.3612"17"20,0000.3125"0.6560.005
A 3X50-SH03C10 0.378"10"2,5000.1875"0.2190.003
A 3X50-SK04E15 0.412"15"13,0000.3125"0.4380.004
A 3X50-SL05F30 0.4325"30"20,0000.375"1.00.005
A 3X50-SH04C14 0.4912"14"2,5000.1875"0.2970.004
A 3X50-SK05E16 0.4912"16"13,0000.3125"0.5630.005
A 3X50-SL06F24 0.5218"24"20,0000.375"0.7810.006
A 3X50-SH04D14 0.6612"14"2,5000.25"0.2970.004
A 3X50-SL06G24 0.718"24"20,0000.5"0.7810.006
A 3X50-SK06F23 0.7118"23"13,0000.375"0.6720.006
A 3X50-SH04E14 0.8312"14"2,5000.3125"0.2970.004
A 3X50-SL08G31 0.9324"31"20,0000.5"1.0470.008
A 3X50-SK06G23 0.9518"23"13,0000.5"0.6720.006
A 3X50-SH05E15 1.0312"15"2,5000.3125"0.3590.005
A 3X50-SK08G30 1.2624"30"13,0000.5"0.8750.008
A 3X50-SL10J33 1.4624"33"20,0000.625"1.3280.010
A 3X50-SH06F21 1.4818"21"2,5000.375"0.4380.006
A 3X50-SK08J30 1.5824"30"13,0000.625"0.8750.008
A 3X50-SH06G21 1.9718"21"2,5000.5"0.4380.006
A 3X50-SK10J32 1.9824"32"13,0000.625"1.1090.010
A 3X50-SL12K42 2.0930"42"20,0000.75"1.5780.012
A 3X50-SK10K32 2.3724"32"13,0000.75"
A 3X50-SH08G28 2.6324"28"2,5000.5"
A 3X50-SL12P42 2.830"42"20,0001"1.5780.012
A 3X50-SK12K40 2.8430"40"13,0000.75"1.3440.012
A 3X50-SH08J28 3.2924"28"2,5000.625"0.5780.008
A 3X50-SL15P46 3.530"46"20,0001"1.9840.015
A 3X50-SK12P40 3.7930"40"13,0001"1.3440.012
A 3X50-SH10J29 4.1224"29"2,5000.625"0.7340.010
A 3X50-SL15R46 4.3730"46"20,0001.25"1.9840.015
A 3X50-SK15P42 4.7430"42"13,0001.0"1.6720.015
A 3X50-SH10K29 4.9524"29"2,5000.75" 0.7340.010
A 3X50-SK18P47 5.6932"47"13,0001.0"2.00.018
A 3X50-SL20R54 5.8336"54"20,0001.25"2.6250.020
A 3X50-SH12K36 5.9430"36"2,5000.75"0.8750.012
A 3X50-SL20S54 6.9936"54"20,0001.5"2.6250.020
A 3X50-SH12P36 7.9230"36"2,5001.0"0.8750.012
A 3X50-SL25S59 8.7436"59"20,0001.5"3.2970.025
A 3X50-SK20S52 9.4836"52"13,0001.5"2.2190.020
A 3X50-SH16P38 10.630"38"2,5001.0"1.1560.016
A 3X50-SL25U59 11.736"59"20,0002.0"3.2970.025
A 3X50-SK25S57 11.936"57"13,0001.5"2.7810.020
A 3X50-SL31U69 14.442"69"20,000
A 3X50-SK25U57 15.836"57"13,0002.0"2.7810.025
A 3X50-SH20R47 16.536"47"2,5001.25"1.4690.020
A 3X50-SK31U68 19.642"68"13,0002.0"3.4380.031
A 3X50-SH20S47 19.836"47"2,5001.5"1.4690.020
A 3X50-SH25S48 24.836"48"2,5001.5"1.8280.025
A 3X50-SH25U48 3336"48"2,5002.0"1.8280.025
A 3X50-SH31U58 40.942"58"2,5002.0"2.2660.031

Available from our distributor, Stock Drive Products. Tel: 516-328-3300

Constant Force Spring Technical Information and Diameter vs. Load Chart (matl: T301 SS, calculations shown are at 1.0" width, interpolate for other spring material widths)

2,500 cycles10,000 cycles20,000 cycles75,000 cycles150,000 cycles
Material ThicknessCoiled Dia.LoadCoiled Dia.LoadCoiled Dia.LoadCoiled Dia.LoadCoiled Dia.Load
0.002 0.220.650.330.320.440.17

0.0050.363.30.432.50.551.60.81 0.801.110.44
0.0060.444.00.51 3.00.652.00.951.001.330.52
0.0080.595.2 0.694.00.872.61.28 1.301.780.70
0.0120.878. 1.04
0.0161.1610.61.37 8.01.735.32.532.703.601.40
0.0201.4613.21.71 10.02.18
0.0221.6114.5 1.8911.02.377.23.483.604.891.91
0.0251.8116.52.1412.52.728.24.004.10 5.552.18
0.031 2.2620.5 2.6515.53.3610.24.945.106.902.70
STOCK Constant Force Spring Selection Chart CLICK for a larger selection chart, LIVE data & ordering links!
STOCK Constant Force Spring Selection Chart

Order small quantities (click chart shown above).

Large Multi-Leaf (interwound), Highly Specialized End Detail & Sub-Miniature Constant Force Spring Examples

Constant Force Springs1
Constant Force Springs2
Constant Force Springs3
Download .pdf
"Stock" Constant Force Springs

“Stock” Constant Force Spring Selection Chart w/links

Constant Force Balance Springs Download .pdf
Constant Force Balance Springs

Info Sheet

Point Of Purchase Download .pdf
Point Of Purchase

“Pusher” Variable Force Spring

Window Balance Springs Download .pdf
Window Balance Springs

1/2″ Constant Force Window Balance Selection Guide

Window Balance Springs Download .pdf
Window Balance Springs

3/4″ Constant Force Window Balance Selection Guide

Need Assistance? Consult our Technical Team.

Our Technical Team offer a depth of expertise to assist you with all parts of the process. We are ready to answer your questions in a timely manner and will help you define what you need. We produce custom springs for all purposes, and we are here to work with you on any of your customization needs.