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.)
0.0020.151.30.1710.220.650.330.320.440.17
0.0030.2220.251.50.3210.480.50.660.26
0.0040.32.60.3420.441.30.650.650.890.35
0.0050.363.30.432.50.551.60.810.81.110.44
0.0060.4440.5130.6520.9511.330.52
0.0080.595.20.6940.872.61.281.31.780.7
0.010.736.60.8651.083.31.591.62.220.87
0.0120.8781.0361.341.9122.671.04
0.0141.029.31.271.524.62.222.33.071.2
0.0161.1610.61.3781.735.32.532.73.61.4
0.0181.3111.91.5491.965.92.85341.56
0.021.4613.21.71102.186.63.23.34.441.74
0.0221.6114.51.89112.377.23.483.64.891.91
0.0251.8116.52.1412.52.728.244.15.552.18
0.0282.0418.52.4143.049.54.484.66.232.44
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"
1.1090.010
A 3X50-SH08G28 2.6324"28"2,5000.5"
0.5780.008
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
2.0"4.0780.031
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
0.151.30.171.0 0.220.650.330.320.440.17

0.003
0.222.00.251.50.321.00.480.500.660.26
0.0040.302.60.341.50.441.30.650.650.890.35
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
0.0100.736.60.865.01.083.31.591.602.220.87
0.0120.878.01.036.01.304.01.912.002.67 1.04
0.0141.029.31.207.01.524.62.222.303.071.20
0.0161.1610.61.37 8.01.735.32.532.703.601.40
0.0181.3111.91.549.01.965.92.853.004.001.56
0.0201.4613.21.71 10.02.18 6.63.203.304.441.74
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
0.0282.0418.52.4014.03.049.54.484.606.232.44
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
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"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

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