spring-calculations-V3-by-kaje.xlsx

	A	B	C
1	Spring Calculations (Compression Springs) – V3
2
3		NOTE: This spreadsheet is intended primarily for use with compression springs, but can be used to a limited extent for extension and torsion spring also. Updates to this spreadsheet may be made to correct errors or add new features. Go to the link below to download the most recent version:
4
5		https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/tools---spring-making
6
7		This spreadsheet includes seven sheets as follows:
8
9		1.	Introduction: This introduction. Note: This spreadsheet is “protected” to prevent accidental changes, but here is no password so this can be turned off if necessary.
10
11		2.	Mandrel: Calculate the mandrel size needed to wind a spring of a specified diameter.
12
13		3.	Equivalent: Given a set of spring parameters, find the parameters for a spring with the same spring rate but with a different wire size, diameter, number of coils, etc.
14
15		4.	Table: A simple lookup table to find arbor (mandrel) diameters for winding music wire springs of a designated size.
16
17		5.	Illustrations: Pictures to help explain other parts of the spreadsheet (for example, types of spring ends)..
18
19		6.	Data: Tables of data and calculations used to derive formulas for mandrel calculations. This is included for the benefit of those who would like to know how the calculations were determined.
20
21		7.	Versions: List of versions of this spreadsheet with the changes or additions made in each new version.
22
23	Errors, recommendations, or comments?
24	If you find any errors in this spreadsheet, or if you would like to recommend any improvements or request new features, please send an email to this address:
25	kaje567@gmail.com
26
27	This spreadsheet is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License unless otherwise noted. Please cite all use of this chart as follows: From Academy of Lagado [https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/tools---spring-making ] by kaje , used under a Creative Commons Attribution-ShareAlike license: http://creativecommons.org/licenses/by-sa/3.0/

	A	B	C	D	G	H	I	K	L	M	N
1	Spring Equivalent
2
3	This sheet allows you to calculate the required parameters to make a “matching” spring (that is, a spring with the equivalent spring rate) when you need to change one or more spring parameters.
4
5	INSTRUCTIONS – STEP 1: For the spring you want to match (“original” spring), make the appropriate data entries below:				INSTRUCTIONS: STEP 2: Enter the desired parameters for the new spring you want to make. Enter any two of the following: wire diameter, spring diameter, and number of active coils. The parameter that is left blank will be calculated. You may enter a different spring length, otherwise the length from Step 1 will be used. Options in yellow cells may also be changed.
6
7	blue cells :	Enter required data			blue cells :	Enter required data
8	yellow cells :	Click to make a selection			yellow cells :	Click to make a selection
9	green cells :	Calculated results			green cells :	Calculated results
10
11	Spring to be matched				Parameters for equivalent spring			Equivalent spring results below
12
13	Wire diameter (inches)	0.0220			Wire diameter (inches)	0.0250		Wire diameter (inches)	0.0250
14	Spring diameter (inches)	0.188	Inner diameter		Spring diameter (inches)	0.188	I,O,M same as original	Spring diameter (inches)	0.188	Inner diameter
15	Type of wire (select)	Music wire			Type of wire (select)	Same as original		Type of wire	Music wire
16	Type of spring end (select)	Open ends		See illustrations sheet for examples.	Type of spring end (select)	Same as original		Type of spring end	Open ends		See illustrations sheet for examples.
17	Number of active coils	9			Number of active coils		Leave blank to calculate	Number of active coils	14
18	Length of spring (inches)	0.625			Length of spring (inches)	0.625	Same as original	Length of spring (inches)	0.625
19					Length of spring (inches)		Change length (optional)
20
21	Inner coil diameter (inches)	0.188			Inner coil diameter (inches)	0.163		Inner coil diameter (inches)	0.188
22	Mean coil diameter (inches)	0.210			Mean coil diameter (inches)	0.188		Mean coil diameter (inches)	0.213
23	Outer coil diameter (inches)	0.232			Outer coil diameter (inches)	0.213		Outer coil diameter (inches)	0.238
24	Spring index (D/d)	9.5	Spring index is within recommended range of 5 to 15.		Spring index (D/d)	7.5		Spring index (D/d)	8.5	Spring index is within recommended range of 5 to 15.
25
26	Number of total coils	9	(Includes both active and inactive coils)					Number of total coils	14	(Includes both active and inactive coils)
27	Number of “wires”	10						Number of “wires”	15
28	Solid height (inches)	0.220						Solid height (inches)	0.375
29	Maximum travel (inches)	0.405						Maximum travel (inches)	0.250
30	Length of wire needed (inches)	5.9	See note below.					Length of wire needed (inches)	9.4	See note below.
31	Spring Rate (Lbs/in)	4.038						Spring Rate (Lbs/in)	4.148	(102.7% of original)
32	Material shear modulus, G (psi)	11,492,970.929						Material shear modulus, G (psi)	11,492,970.929
33
34
35	Note: “Length of wire” is the theoretical length needed for a compression spring. For an extension or torsion spring you will need to add additional length for hooks or legs respectively.				Note: “Length of wire” is the theoretical length needed for a compression spring. For an extension or torsion spring you will need to add additional length for hooks or legs respectively.

	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z	AA	AB	AC
1	Table of Arbor Diameters for Springs Made from Music Wire
2
3	This table is based on data from Machinery's Handbook 28th Ed., page 350, Table 23. Values shown in black are from the original table, values shown in blue are calculated using the formulas from the “Mandrel” sheet of this spreadsheet.
4
5
6												Arbor Diameters for Springs Made from Music Wire
7
8
9						Spring Outside Diameter (inch)
10
11	Wire Dia. (inch)	1/16		3/32		1/8		5/32		3/16		7/32		1/4		9/32		5/16		11/32		3/8		7/16		1/2
12		0.0625		0.09375		0.125		0.15625		0.1875		0.21875		0.25		0.28125		0.3125		0.34375		0.375		0.4375		0.5
13
14										Arbor Diameter (inch)
15
16	0.008	0.039	0.041	0.060	0.064	0.078	0.086	0.093	0.105	0.107	0.123	0.119	0.140	0.129	0.157	...		...		...		...		...		...
17	0.01	0.037	0.038	0.060	0.063	0.080	0.086	0.099	0.107	0.115	0.127	0.129	0.145	0.142	0.163	0.154	0.180	0.164	0.196	...		...		...		...
18	0.012	0.034	0.035	0.059	0.061	0.081	0.085	0.101	0.108	0.119	0.129	0.135	0.148	0.150	0.167	0.163	0.185	0.177	0.202	0.189	0.219	0.200	0.235	...		...
19	0.014	0.031	0.032	0.057	0.059	0.081	0.084	0.102	0.107	0.121	0.129	0.140	0.150	0.156	0.170	0.172	0.188	0.187	0.207	0.200	0.224	0.213	0.241	0.234	0.275	...
20	0.016	0.028	0.028	0.055	0.056	0.079	0.082	0.102	0.106	0.123	0.129	0.142	0.151	0.161	0.171	0.178	0.191	0.194	0.210	0.209	0.228	0.224	0.246	0.250	0.280	0.271	0.314
21	0.018	...		0.053	0.053	0.077	0.079	0.101	0.104	0.124	0.128	0.144	0.151	0.161	0.172	0.182	0.193	0.200	0.213	0.215	0.232	0.231	0.250	0.259	0.286	0.284	0.320
22	0.02	...		0.049	0.049	0.075	0.076	0.096	0.102	0.123	0.126	0.144	0.150	0.165	0.172	0.184	0.194	0.203	0.214	0.220	0.234	0.237	0.253	0.268	0.290	0.296	0.325
23	0.022	...		0.046	0.046	0.072	0.073	0.097	0.100	0.122	0.125	0.145	0.149	0.165	0.172	0.186	0.194	0.206	0.215	0.224	0.236	0.242	0.256	0.275	0.294	0.305	0.330
24	0.024	...		0.043	0.042	0.070	0.070	0.095	0.097	0.120	0.122	0.144	0.147	0.166	0.171	0.187	0.193	0.207	0.215	0.226	0.237	0.245	0.257	0.280	0.296	0.312	0.334
25	0.026	...		...		0.067	0.067	0.093	0.094	0.118	0.120	0.143	0.145	0.166	0.169	0.187	0.193	0.208	0.215	0.228	0.237	0.248	0.258	0.285	0.298	0.318	0.337
26	0.028	...		...		0.064	0.064	0.091	0.091	0.115	0.117	0.141	0.143	0.165	0.167	0.187	0.191	0.208	0.214	0.229	0.237	0.250	0.258	0.288	0.300	0.323	0.339
27	0.03	...		...		0.061	0.060	0.088	0.088	0.113	0.115	0.138	0.140	0.163	0.165	0.187	0.190	0.209	0.213	0.229	0.236	0.251	0.258	0.291	0.301	0.328	0.341
28	0.032	...		...		0.057	0.057	0.085	0.085	0.111	0.112	0.136	0.138	0.161	0.163	0.185	0.188	0.209	0.212	0.229	0.235	0.251	0.258	0.292	0.301	0.331	0.343
29	0.034	...		...		...		0.082	0.081	0.109	0.109	0.134	0.135	0.159	0.161	0.184	0.186	0.208	0.210	0.229	0.234	0.251	0.257	0.292	0.301	0.333	0.344
30	0.036	...		...		...		0.078	0.078	0.106	0.105	0.131	0.132	0.156	0.158	0.182	0.184	0.206	0.208	0.229	0.232	0.250	0.256	0.294	0.301	0.333	0.344
31	0.038	...		...		...		0.075	0.074	0.103	0.102	0.129	0.129	0.154	0.156	0.179	0.181	0.205	0.206	0.227	0.231	0.251	0.255	0.293	0.301	0.335	0.345
32	0.041	...		...		...		...		0.098	0.097	0.125	0.125	0.151	0.151	0.176	0.177	0.201	0.203	0.226	0.228	0.250	0.252	0.294	0.299	0.336	0.344
33	0.0475	...		...		...		...		0.087	0.086	0.115	0.114	0.142	0.141	0.168	0.168	0.194	0.194	0.220	0.220	0.244	0.245	0.293	0.294	0.337	0.342
34	0.054	...		...		...		...		...		0.103	0.103	0.132	0.131	0.160	0.158	0.187	0.185	0.212	0.211	0.245	0.237	0.287	0.288	0.336	0.337
35	0.0625	...		...		...		...		...		...		0.108	0.116	0.146	0.144	0.169	0.172	0.201	0.199	0.228	0.225	0.280	0.278	0.330	0.328
36	0.072	...		...		...		...		...		...		...		0.129	0.127	0.158	0.156	0.186	0.183	0.214	0.211	0.268	0.264	0.319	0.317
37	0.08	...		...		...		...		...		...		...		...		0.144	0.142	0.173	0.170	0.201	0.198	0.256	0.252	0.308	0.305
38	0.0915	...		...		...		...		...		...		...		...		...		...		0.181	0.178	0.238	0.234	0.293	0.288
39	0.1055	...		...		...		...		...		...		...		...		...		...		...		0.215	0.210	0.271	0.265
40	0.1205	...		...		...		...		...		...		...		...		...		...		...		...		0.215	0.240	Possible error in table?
41	0.125	...		...		...		...		...		...		...		...		...		...		...		...		0.239	0.232
42
43						Spring Outside Diameter (inch)
44
45	Wire Dia. (inch)	9/16		5/8		11/16		3/4		13/16		7/8		15/16		1		1-1/8		1-1/4		1-3/8		1-1/2		1-3/4		2
46		0.5625		0.625		0.6875		0.75		0.8125		0.875		0.9375		1		1.125		1.25		1.375		1.5		1.75		2
47
48										Arbor Diameter (inch)
49
50	0.022	0.332	0.364	0.357	0.398	0.380	0.432	...		...		...		...		...		...		...		...		...		...		...
51	0.024	0.341	0.369	0.367	0.404	0.393	0.438	0.415	0.471	...		...		...		...		...		...		...		...		...		...
52	0.026	0.350	0.373	0.380	0.409	0.406	0.443	0.430	0.477	...		...		...		...		...		...		...		...		...		...
53	0.028	0.356	0.377	0.387	0.413	0.416	0.448	0.442	0.482	0.467	0.516	...		...		...		...		...		...		...		...		...
54	0.03	0.362	0.380	0.395	0.417	0.426	0.453	0.453	0.488	0.481	0.522	0.506	0.555	...		...		...		...		...		...		...		...
55	0.032	0.367	0.382	0.400	0.420	0.432	0.457	0.462	0.492	0.490	0.527	0.516	0.561	0.540	0.594	...		...		...		...		...		...		...
56	0.034	0.370	0.384	0.404	0.423	0.437	0.460	0.469	0.497	0.498	0.532	0.526	0.566	0.552	0.600	0.557	0.634	...		...		...		...		...		...
57	0.036	0.372	0.386	0.407	0.425	0.442	0.463	0.474	0.500	0.506	0.536	0.536	0.571	0.562	0.606	0.589	0.640	...		...		...		...		...		...
58	0.038	0.375	0.387	0.412	0.427	0.448	0.466	0.481	0.504	0.512	0.540	0.543	0.576	0.572	0.611	0.600	0.645	0.650	0.712	...		...		...		...		...
59	0.041	0.378	0.387	0.416	0.429	0.456	0.469	0.489	0.508	0.522	0.545	0.554	0.582	0.586	0.618	0.615	0.653	0.670	0.721	0.718	0.788	...		...		...		...
60	0.0475	0.380	0.387	0.422	0.431	0.464	0.473	0.504	0.514	0.541	0.554	0.576	0.592	0.610	0.630	0.643	0.666	0.706	0.737	0.763	0.806	0.812	0.874	...		...		...
61	0.054	0.381	0.384	0.425	0.429	0.467	0.474	0.509	0.516	0.550	0.558	0.589	0.598	0.625	0.638	0.661	0.676	0.727	0.751	0.792	0.822	0.850	0.891	0.906	0.959	...		...
62	0.0625	0.379	0.377	0.426	0.425	0.468	0.471	0.512	0.516	0.556	0.560	0.597	0.602	0.639	0.644	0.678	0.685	0.753	0.763	0.822	0.838	0.889	0.911	0.951	0.981	1.060	1.118	1.170	1.251
63	0.072	0.370	0.367	0.418	0.417	0.466	0.465	0.512	0.512	0.555	0.558	0.599	0.602	0.641	0.646	0.682	0.689	0.765	0.771	0.840	0.850	0.911	0.927	0.980	1.001	1.110	1.143	1.220	1.279
64	0.08	0.360	0.357	0.411	0.408	0.461	0.458	0.509	0.506	0.554	0.553	0.599	0.599	0.641	0.645	0.685	0.689	0.772	0.774	0.851	0.857	0.930	0.936	1.000	1.013	1.130	1.160	1.260	1.300
65	0.0915	0.347	0.341	0.398	0.394	0.448	0.445	0.500	0.495	0.547	0.544	0.597	0.592	0.640	0.639	0.685	0.685	0.776	0.775	0.860	0.861	0.942	0.944	1.020	1.025	1.160	1.180	1.300	1.326
66	0.1055	0.327	0.320	0.381	0.374	0.433	0.426	0.485	0.478	0.535	0.529	0.586	0.579	0.630	0.628	0.683	0.676	0.775	0.769	0.865	0.860	0.952	0.947	1.040	1.032	1.200	1.195	1.350	1.349
67	0.1205	0.303	0.296	0.358	0.350	0.414	0.404	0.468	0.457	0.520	0.510	0.571	0.561	0.622	0.612	0.673	0.661	0.772	0.759	0.864	0.853	0.955	0.944	1.040	1.033	1.220	1.204	1.380	1.366
68	0.125	0.295	0.288	0.351	0.343	0.406	0.397	0.461	0.451	0.515	0.503	0.567	0.555	0.617	0.606	0.671	0.656	0.770	0.755	0.864	0.850	0.955	0.942	1.050	1.032	1.230	1.205	1.390	1.369

	A	B	C	D	F	G	H	I
1	Estimated Mandrel Size for Spring Winding
2
3	This spreadsheet calculates the required mandrel size for music wire, stainless steel, and phosphor-bronze spring wire. The calculations are based on formulas and data from the article Design and Wind Your Helical Springs by Kozo Hiraoko. The X' and Y' data below were taken from measurements on the chart in the original article, which were then converted to the X and Y values corresponding to the chart values. A polynomial fit was calculated for each data set using the CorelPolyGUI Polynomial Regression extension for LibreOffice Calc; the resulting polynomial equations are then used to determine the k value used to estimate the required mandrel size.
4
5
6	Music Wire / Stainless steel						Calculated values
7	X'	Y'	X	Y
8	0.97	2.87	4.97	0.9213	method	polynomial	4.97	0.9218678038
9	1.13	3	5.13	0.92	x data	C3:C17	5.01	0.9212815832
10	1.8	4	5.8	0.91	y data	D3:D17	5.05	0.9206960962
11	2.51	5	6.51	0.9	a[0]	1.00054075	5.09	0.9201113426
12	3.21	6	7.21	0.89	a[1]	-0.0170192551	5.13	0.9195273218
13	3.96	7	7.96	0.88	a[2]	0.0002443660839	5.2975	0.9170896863
14	4.74	8	8.74	0.87	a[3]	-0.000001004455418	5.465	0.9146648671
15	5.47	9	9.47	0.86	R²	0.9999567197	5.6325	0.9122528357
16	6.3	10	10.3	0.85	date	04/14/15	5.8	0.909853564
17	7.15	11	11.15	0.84	time	12:34:38 PM	5.9775	0.9073249457
18	7.98	12	11.98	0.83			6.155	0.9048105905
19	8.88	13	12.88	0.82			6.3325	0.9023104647
20	9.73	14	13.73	0.81			6.51	0.8998245346
21	10.71	15	14.71	0.8			6.685	0.8973874819
22	10.98	15.3	14.98	0.797			6.86	0.8949641628
23							7.035	0.8925545451
24							7.21	0.8901585963
25							7.3975	0.8876066399
26							7.585	0.8850702983
27							7.7725	0.8825495315
28							7.96	0.8800442999
29							8.155	0.877455296
30							8.35	0.8748830073
31							8.545	0.8723273891
32							8.74	0.8697883968
33							8.9225	0.8674271821
34							9.105	0.8650804542
35							9.2875	0.8627481765
36							9.47	0.8604303124
37							9.6775	0.8578123966
38							9.885	0.8552130126
39							10.0925	0.8526321066
40							10.3	0.8500696246
41							10.5125	0.8474644352
42							10.725	0.8448784542
43							10.9375	0.8423116237
44							11.15	0.839763886
45							11.3575	0.8372944638
46							11.565	0.8348431375
47							11.7725	0.8324098532
48							11.98	0.829994557
49							12.205	0.8273958262
50							12.43	0.8248181138
51							12.655	0.822261351
52							12.88	0.8197254692
53							13.0925	0.817349581
54							13.305	0.814992199
55							13.5175	0.8126532654
56							13.73	0.8103327225
57							13.975	0.8076800222
58							14.22	0.8050516026
59							14.465	0.802447375
60							14.71	0.7998672507
61							14.7775	0.7991606235
62							14.845	0.7984558173
63							14.9125	0.7977528303
64							14.98	0.7970516605
65
66
67
68
69
70	Phosphor/Bronze Wire						Calculated values
71	X'	Y'	X	Y
72	0.98	1.72	4.98	0.9328	method	polynomial	4.98	0.9327471516
73	1.2	2	5.2	0.93	x data	C67:C79	5.035	0.93203826
74	1.97	3	5.97	0.92	y data	D67:D79	5.09	0.9313306252
75	2.8	4	6.8	0.91	a[0]	1.002463668	5.145	0.9306242446
76	3.64	5	7.64	0.9	a[1]	-0.01516064153	5.2	0.9299191156
77	4.42	6	8.42	0.89	a[2]	0.0002457345713	5.3925	0.9274609848
78	5.39	7	9.39	0.88	a[3]	-0.000002516782186	5.585	0.9250180485
79	6.33	8	10.33	0.87	R²	0.9997475837	5.7775	0.922590199
80	7.26	9	11.26	0.86	date	04/14/15	01/04/00	0.9201773285
81	8	10	12	0.85	time	05:46:18 PM	04:15:36 AM	0.9175930937
82	9.16	11	13.16	0.84			6.385	0.9150260033
83	10.19	12	14.19	0.83			6.5925	0.9124759223
84	11	12.83	15	0.8217			6.8	0.9099427157
85							7.01	0.9073960315
86							7.22	0.9048663527
87							7.43	0.9023535397
88							7.64	0.8998574525
89							7.835	0.8975545115
90							8.03	0.8952657597
91							8.225	0.8929910852
92							8.42	0.8907303759
93							8.6625	0.8879382945
94							8.905	0.8851674221
95							9.1475	0.8824175434
96							9.39	0.879688443
97							9.625	0.8770633688
98							9.86	0.8744574094
99							10.095	0.8718703687
100							10.33	0.8693020508
101							10.5625	0.8667792884
102							10.795	0.8642744709
103							11.0275	0.8617874086
104							11.26	0.8593179117
105							11.445	0.8573653583
106							11.63	0.8554237104
107							11.815	0.8534928724
108							12	0.8515727487
109							12.29	0.8485841579
110							12.58	0.8456212917
111							12.87	0.8426837819
112							13.16	0.8397712602
113							13.4175	0.837205789
114							13.675	0.8346594707
115							13.9325	0.8321320475
116							14.19	0.8296232616
117							14.3925	0.8276632559
118							14.595	0.8257144914
119							14.7975	0.8237768426
120							15	0.8218501842

	A	B
1	Version changes for this spreadsheet
2
3	Version 1:	Original version, has no version number.
4		This version did mandrel calculations only.
5
6	Version 2:	Added spring index calculation, with warning flag if outside recommended range..
7		Increased number of decimal places for wire diameter from 3 to 4
8		Added table from Machinery's Handbook 28th Ed.
9		Re-arranged sheets
10		Added additional calculations and illustrations
11
12	Version 3:	Revised file name from “mandrel-adjustment” to “spring calculations”
13		Added sheet to calculate spring equivalent.
14		Added warning re active coils must be less than or equal to total coils.
15		Corrected formatting errors.
16		Added warning if spring length is <= solid height
17		Reorganized cells to simplify data entry.
18		Added sheet protections to prevent accidental changes (there are no passwords so you can turn this off if you want to make modifications)

	A	B	C	D
1	Estimated Mandrel Size for Spring Winding – Version 2.0
2	with Additional Spring Calculations
3
4	This spreadsheet calculates the required mandrel size for music wire, stainless steel, and phosphor-bronze spring wire. The calculations are based on formulas and data from the article Design and Wind Your Helical Springs by Kozo Hiraoko (Part 1 page 20 Home Shop Machinist 1987 May-Jun, part 2 page 30 Home Shop Machinist 1987 Jul-Aug). Enter the required values in the blues boxes; click on the yellow box and then the arrow and select the correct entry from the drop down. Results are shown in the green boxes. For more information on this spreadsheet, go here: https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/tools---spring-making This spreadsheet is primarily for COMPRESSION SPRINGS, although the mandrel recommendations can also be applied to extension and torsion springs.
5
6	Wire diameter (inches)	0.0220
7	Spring diameter (inches)	0.188	Inner diameter
8	Type of wire (select)	Music wire
9	Mandrel diameter (inches)	0.158	for Music wire
10	Mandrel diameter (inches)	0.158	for Stainless Steel wire
11	Mandrel diameter (inches)	0.162	for Phosphor-bronze wire
12
13	Inner coil diameter (inches)	0.188
14	Mean coil diameter (inches)	0.210
15	Outer coil diameter (inches)	0.232
16
17	Spring index (D/d)	9.5	Spring index is within recommended range of 5 to 15.
18
19
20	For additional spring calculations, enter data in the blue boxes below:
21
22	Type of spring end (select)	Open ends		See illustrations sheet for examples.
23	Length of spring (inches)	0.625
24	Number of active coils	14
25	Number of total coils	14	(Includes both active and inactive coils)
26	Number of “wires”	15
27	Solid height (inches)	0.330
28	Maximum travel (inches)	0.295
29	Length of wire needed (inches)	9.2	See note below.
30	Spring Rate (Lbs/in)	2.596
31	Material shear modulus, G (psi)	11,492,970.929
32
33
34	Note: “Length of wire” is the theoretical length needed for a compression spring. For an extension or torsion spring you will need to add additional length for hooks or legs respectively.

	A	B	C	D	E	F	G	H	I	J	K
1
2
3	The illustration below shows the variables used to calculate required mandrel size.
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31	The illustration below shows different kinds of spring end types.
32
33	The equations for calculating “solid height” (the height of a fully compressed spring) are shown below.
34
35
36
37
38	Closed and square ends:
39	Total Wires = Total Coils + 1
40	Solid Height = Total Wire * Wire Diameter
41	Has 2 inactive coils.
42
43
44
45
46
47
48
49	Closed and ground ends:
50	Total Wires = Total Coils
51	Solid Height = Total Wire * Wire Diameter
52	Has 2 inactive coils.
53
54
55
56
57
58
59
60	Double closed ends:
61	Total Wires = Total Coils + 1
62	Solid Height = Total Wire * Wire Diameter
63	Has 4 inactive coils.
64
65
66
67
68
69
70
71
72	Open ends:
73	Total Wires = Total Coils + 1
74	Solid Height = Total Wire * Wire Diameter
75	Has 0 inactive coils.
76
77
78
79
80