What is a spring washer

What is a spring washer

What is a spring washer?

Spring washer is widely used in load-bearing and non load-bearing structures of general mechanical products. It is characterized by low cost and convenient installation. It is suitable for parts with frequent assembly and disassembly. It is made of stainless steel and carbon steel, which is iron. The commonly used spring washers are M3, M4, M5, M6, M8, M10, M12, M14 and M16. These specifications are commonly used.

Principle and function of spring washer

Function of spring washer:
The basic function of the spring washer is to give a force to the nut after the nut is tightened and increase the friction between the nut and bolt. That is, a protective measure added to prevent the loosening of fastening bolts caused by equipment vibration in operation.
Locking principle of spring washer:
The anti loosening principle of the spring washer is that after the spring washer is flattened, the spring washer will produce a continuous elastic force, so that the threaded connection pair of the nut and the bolt can maintain a friction force and produce a resistance torque, so as to prevent the nut from loosening. At the same time, the sharp corners at the opening of the spring washer are respectively embedded in the surface of the bolt and the connected piece, so as to prevent the bolt from rotating relative to the connected piece.
However, practice has proved that the spring washer can only provide an elastic force of 10 N/m, and the elastic force of 10 N/M can be ignored for the bolt pre tightening torque of 280 n/m. Secondly, such a small force is not enough to embed the sharp corner at the notch of the spring washer into the surface of the bolt and the connected part. After disassembly, there is no obvious embedded mark on the surface of the bolt and the connected part. Therefore, the anti loosening effect of spring washer on bolt can be ignored.

What is the locking effect of the spring washer?

Spring washer is widely used in load-bearing and non load-bearing structures of general mechanical products. It is characterized by low cost and convenient installation. It is suitable for parts with frequent assembly and disassembly. However, the anti loosening ability of spring washer is very low. Especially at present, the adoption rate of products requiring high reliability in European and American countries is very low, especially the important connection parts of load-bearing structures have been abandoned for many years. Our country still has some applications in military industry, but it has been improved to stainless steel. It is said that steel spring washers have long been banned in CASC. In other words, it is very unsafe for two reasons: one is the rising circle and the other is hydrogen embrittlement.

Case of spring washer locking

Grade 10.9 M16 is used for the connection between axle final drive and axle housing × 100 bolts, with a tightening torque of (280 + 20) n · m, which are tightened by a high-precision electric tightening machine. The change of torque with angle during bolt tightening is detected under the conditions of spring washer and no spring washer. Comparing the torque angle curve, it is found that there is always about 10N · m pre tightening torque in the case of spring washer; Without the spring washer, the torque of the bolt is in the state of 0n · m before the torque increases significantly.
It can be inferred that the spring washer can be completely flattened with a bolt pre tightening torque of about 10N · M. Through the inspection with digital display torque wrench, it is found that the bolt torque has not reached 20n · m and the spring washer has been completely flattened, which verifies the correctness of the above inference.
The analysis of the above two points shows that the spring washer can only provide 10N · m elastic force, and the 10N · m elastic force can be ignored for the bolt pre tightening torque of 280 n · M. secondly, such a small force is not enough to embed the sharp corner at the notch of the spring washer into the surface of the bolt and the connected part. After disassembly, there is no obvious embedded mark on the surface of the bolt and the connected part. Therefore, the anti loosening effect of spring washer on bolt can be ignored.
In addition, a washer is added between the bolt and the connected part. If there is a problem with the quality of the washer, it is equivalent to adding another potential safety hazard to the bolt connection.
To sum up, when the bolt torque is large (greater than 200N · m), the way of locking the bolt with spring washer does more harm than good. Therefore, under the action of impact, vibration and variable load, the preload may disappear at a moment, and the connection may be loosened.
At the same time, NASA also found the problem of open spring washer. In the lock nut chapter of NASA standard, it wrote: “typical coil spring washer… Acts as a spring when the bolt is tightened. However, when the bolt is fully tightened, the washer is generally flat. At this time, it can be regarded as an integrated flat washer, and its locking function does not exist at all. In short, this type of lock washer is good for nothing in terms of locking. ” See the following figure for an excerpt from the original text.

However, some professionals disagree with this statement.

Material of spring washer

65Mn spring steel or 70# carbon steel, 3Cr13, stainless steel SUS304 or SUS316 and phosphor bronze are usually used.

Standard for spring washers

Chinese spring washer performance standard GB/T 94.1

• (1) Hardness: 42 ~ 50HRC.
• (2) Elasticity: after continuously loading and flattening the steel spring washer for three times, measure the free height, which shall not be less than 1.67s nominal.
• (3) Toughness: clamp the steel spring washer on the Bench Vise and twist it for 90o without fracture.

German spring washer performance standard DIN267T26

• (1) Hardness: 430 ~ 530hv.
• (2) Permanent deformation test: after pressing the steel spring washer for 2min, measure the free height, which shall not be less than DIN267T26.
• (3) Permanent load test: separate 10 spring washers with 10 flat washers, put them on the test bar, and the washers shall not break after pressing for 48h.
• (4) Torsion test: the steel spring washer shall be clamped on the bench vice and shall not be broken after being twisted for 90o. Continue to load until it is broken, and the section shall be smooth.
• (5) Elasticity test: after pressing the steel spring washer for 2min, loosen it for 20 minutes μ m. The residual elastic force shall comply with the provisions of DIN267T26.

American spring washer performance standard ASME B18.21.1

• (1) Hardness: 38 ~ 46hrc.
• (2) Elasticity test: after flattening the steel spring washer, measure the free height, which shall not be less than 2 / 3 of the original height.
• (3) Torsion test: the steel spring washer shall be clamped on the bench vice and shall not be broken after being twisted for 90o.

British spring washer performance standard BS1802

• (1) Hardness: 42 ~ 50HRC.
• (2) Elasticity: load the steel spring washer so that it is completely flattened. The free height measured after the tea is released shall not be less than 1.66s nominal. Then apply and release the load continuously for 20 times, and its free height shall not be further reduced.

In addition, for the plated spring washer, hydrogen drive treatment shall be carried out immediately after plating. The washer shall be flattened and placed for more than 48h after electroplating to observe whether brittle fracture occurs.

Standard spring washer size table

Spring washer dimensions chart for regular standard helical spring-lock washers according to ASME B18.21.1 “Washers: Helical Spring-Lock, Tooth Lock, and Plain Washers (Inch Series) ” standard.

Nominal Size (Nominal Thread dia., d)	Inside Dia. A		Max. Outside Dia.	Min. Mean Section Thickness (ti + to)/2	Min.  Section Width	Min. Bearing Width
	max.	min.	B	T	W	BW
No.2 (0.086)	0.094	0.088	0.172	0.020	0.035	0.024
No.3 (0.099)	0.107	0.101	0.195	0.025	0.040	0.028
No.4  (0.112)	0.120	0.114	0.209	0.025	0.040	0.028
No.5 (0.125)	0.133	0.127	0.236	0.031	0.047	0.033
No.6 (0.138)	0.148	0.141	0.250	0.031	0.047	0.033
No.8 (0.164)	0.174	0.167	0.293	0.040	0.055	0.038
No.10 (0.190)	0.200	0.193	0.334	0.047	0.062	0.043
No.12 (0.216)	0.227	0.220	0.377	0.056	0.070	0.049
1/4 (0.250)	0.260	0.252	0.487	0.062	0.109	0.076
5/16 (0.3125)	0.322	0.314	0.583	0.078	0.125	0.087
3/8 (0.375)	0.385	0.377	0.680	0.094	0.141	0.099
7/16 (0.4375)	0.450	0.440	0.776	0.109	0.156	0.109
1/2 (0.500)	0.512	0.502	0.869	0.125	0.171	0.120
9/16 (0.5625)	0.574	0.564	0.965	0.141	0.188	0.132
5/8 (0.625)	0.641	0.628	1.073	0.156	0.203	0.142
11/16 (0.6875)	0.704	0.691	1.170	0.172	0.219	0.153
3/4 (0.750)	0.766	0.753	1.265	0.188	0.234	0.164
13/16 (0.8125)	0.832	0.816	1.363	0.203	0.250	0.175
7/8 (0.875)	0.894	0.878	1.459	0.219	0.266	0.186
15/16 (0.9375)	0.958	0.941	1.556	0.234	0.281	0.197
1 (1.000)	1.024	1.003	1.656	0.250	0.297	0.208
1 1/16 (1.0625)	1.087	1.066	1.751	0.266	0.312	0.218
1 1/8 (1.125)	1.153	1.129	1.847	0.281	0.328	0.230
1 3/16 (1.1875)	1.217	1.192	1.943	0.297	0.344	0.241
1 1/4 (1.250)	1.280	1.254	2.036	0.312	0.359	0.251
1 5/16 (1.3125)	1.344	1.317	2.133	0.328	0.375	0.262
1 3/8 (1.375)	1.408	1.379	2.219	0.344	0.391	0.274
1 7/16 (1.4375)	1.472	1.442	2.324	0.359	0.406	0.284
1 1/2 (1.500)	1.534	1.504	2.419	0.375	0.422	0.295
1 5/8 (1.625)	1.663	1.633	2.553	0.389	0.424	0.297
1 3/4 (1.750)	1.789	1.758	2.679	0.389	0.424	0.297
1 7/8 (1.875)	1.914	1.883	2.811	0.422	0.427	0.299
2 (2.000)	2.039	2.008	2.936	0.422	0.427	0.299
2 1/4 (2.250)	2.293	2.262	3.221	0.440	0.442	0.309
2 1/2 (2.500)	2.543	2.512	3.471	0.440	0.442	0.309
2 3/4 (2.750)	2.793	2.762	3.824	0.458	0.491	0.344
3 (3.000)	3.043	3.012	4.074	0.458	0.491	0.344

Note : Dimensions are in inches. (from: amesweb.info)

DIN127 standard spring washer

DIN127 spring pad refers to the German standard din127-1987. DIN127 spring pad is divided into type A and type B.
Din127-A heavy spring washer with specification of 6-36mm is specified.
Din127-A heavy spring washer drawing:

Specification and standard parameters of DIN127-A heavy spring washer:

Major diameter of thread	d		d2	b			s			h
	min	max	max	Nominal	min	max	Nominal	min	max	min	max
6	6.1	6.5	11.8	2.5	2.35	2.65	1.6	1.5	1.7	3.6	4.2
8	8.1	8.5	14.8	3	2.85	3.15	2	1.9	2.1	4.6	5.4
10	10.2	10.7	18.1	3.5	3.3	3.7	2.2	2.05	2.35	5	5.9
12	12.2	12.7	21.1	4	3.8	4.2	2.5	2.35	2.65	5.8	6.8
14	14.2	14.7	24.1	4.5	4.3	4.7	3	2.85	3.15	6.8	8
16	16.2	17	27.4	5	4.8	5.2	3.5	3.3	3.7	7.8	9.2
18	18.2	19	29.4	5	4.8	5.2	3.5	3.3	3.7	7.8	9.2
20	20.2	21.2	33.6	6	5.8	6.2	4	3.8	4.2	8.8	10.4
22	22.5	23.5	35.9	6	5.8	6.2	4	3.8	4.2	8.8	10.4
24	24.5	25.5	40	7	6.75	7.25	5	4.8	5.2	11	13
27	27.5	28.5	43	7	6.75	7.25	5	4.8	5.2	11	13
30	30.5	31.7	48.2	8	7.75	8.25	6	5.8	6.2	13.6	16.1
33	33.5	34.7	51.2	8	7.75	8.25	6	5.8	6.2	13.6	16.1
36	36.5	37.7	58.2	10	9.75	10.25	6	5.8	6.2	13.6	16.1

DIN127 spring washer type B standard

Din127-B standard spring washer specifies standard spring washer with specification of 2-48mm.

Din127-B standard spring washer drawing:

Din127-B standard spring pad specification and standard parameter table:

Major diameter of thread	d		d2	b			s			h
	min	max	max	Nominal	min	max	Nominal	min	max	min	max
2	2.1	2.4	4.4	0.9	0.8	1	0.5	0.4	0.6	1	1.2
2.5	2.6	2.9	5.1	1	0.9	1.1	0.6	0.5	0.7	1.2	1.4
3	3.1	3.4	6.2	1.3	1.2	1.4	0.8	0.7	0.9	1.6	1.9
4	4.1	4.4	4.6	1.5	1.4	1.6	0.9	0.8	1	1.8	2.1
5	5.1	5.4	9.2	1.8	1.7	1.9	1.2	1.1	1.3	2.4	2.8
6	6.1	6.5	11.8	2.5	2.35	2.65	1.6	1.5	1.7	3.2	3.8
8	8.1	8.5	14.8	3	2.85	3.15	2	1.9	2.1	4	4.7
10	10.2	10.7	18.1	3.5	3.3	3.7	2.2	2.05	2.35	4.4	5.2
12	12.2	12.7	21.1	4	3.8	4.2	2.5	2.35	2.65	5	5.9
14	14.2	14.7	24.1	4.5	4.3	4.7	3	2.85	3.15	6	7.1
16	16.2	17	27.4	5	4.8	5.2	3.5	3.3	3.7	7	8.3
18	18.2	19	29.4	5	4.8	5.2	3.5	3.3	3.7	7	8.3
20	20.2	21.2	33.6	6	5.8	6.2	4	3.8	4.2	8	9.4
22	22.5	23.5	35.9	6	5.8	6.2	4	3.8	4.2	8	9.4
24	24.5	25.5	40	7	6.75	7.25	5	4.8	5.2	10	11.8
27	27.5	28.5	43	7	6.75	7.25	5	4.8	5.2	10	11.8
30	30.5	31.7	48.2	8	7.75	8.25	6	5.8	6.2	12	14.2
33	33.5	34.7	51.2	8	7.75	8.25	6	5.8	6.2	12	14.2
36	36.5	37.7	58.2	10	9.75	10.25	6	5.8	6.2	12	14.2
39	39.5	40.7	61.2	10	9.75	10.25	6	5.8	6.2	12	14.2
42	42.5	43.7	68.2	12	11.75	12.25	7	6.75	7.25	14	16.5
45	45.5	46.7	71.2	12	11.75	12.25	7	6.75	7.25	14	16.5
48	49	50.5	75	12	11.75	12.25	7	6.75	7.25	14	16.5

DIN127 spring pad material
DIN127 spring pad is divided into spring steel and stainless steel according to material.
Spring steels commonly used for spring pads include 65Mn spring steel, 70 spring steel and 60Si2Mn spring steel. The spring steel of each brand shall meet the chemical composition specified in the following table:

Brand	Chemical composition%
	C	Si	Mn	Cr	Ni	Cu	P	S
65Mn	0.62-0.70	0.17-0.37	0.90-1.20	≤0.25	≤0.25	≤0.25	≤0.035	≤0.035
70	0.62-0.75	0.17-0.37	0.50-0.80	≤0.25	≤0.25	≤0.25	≤0.035	≤0.035
60Si2Mn	0.56-0.64	1.50-2.00	0.60-0.90	≤0.35	≤0.35	≤0.25	≤0.035	≤0.035

Stainless steel spring pads are generally 3Cr13, 1Cr18Ni9Ti or SUS304, SUS316.
DIN127 elastic pad material, heat treatment and surface treatment standards are as follows:

Type	Brand	Standard No	Heat treatment	Surface treatment
Spring steel	65Mn	GB1222、GB5222	Quenching and tempering HRC 42~50	Oxidation, phosphating, galvanizing and passivation
	70
	60Si2Mn
Stainless Steel	3Cr13	GB1220	–	–
	1Cr18Ni9Ti
	SUS304	GB3098.6	–	–

Note: the spring pad must be treated with hydrogen displacement immediately after galvanizing. The hardness of heat treatment is only for reference of production process.

Performance of DIN127 spring pad
Elasticity: DIN127 standard spring washer and heavy spring washer shall be loaded continuously for 3 times according to the specified test load, and then their free height shall be measured. The free height after the test shall not be less than 1.67s nominal height. The elasticity of stainless steel and copper gaskets shall be agreed by the supplier and the buyer.
The test load is specified in the following table:

Specifications/mm	2	2.5	3	4	5	6	8	10	12	14	16	18
Test load/N	700	1160	1760	3050	5050	7050	12900	20500	30000	41300	56300	69000

Specifications/mm	20	22	24	27	30	33	36	39	42	45	48
Test load/N	88000	110000	127000	167000	204000	255000	298000	343000	394000	457000	518000

Toughness: clamp the washer between the vice and the wrench so that the distance between the vice and the wrench is equal to one-half of the outer diameter of the washer. When slowly twisting the wrench clockwise for 90 degrees or 45 degrees, visually inspect the washer surface and continue to twist until it is broken. Visually inspect the section. The spring steel washer shall be twisted to 90 degrees, and the stainless steel and copper washer shall be twisted to 45 degrees without fracture. When it is twisted, the section shall be smooth.
Hydrogen embrittlement resistance: the gasket shall be separated by a flat pad, threaded on the test bar for compression, and reach the test load specified in the table above. It shall be placed for more than 48h and then loosened. The gasket surface shall be visually inspected and shall not be broken after the test.
Surface defects: the gasket surface shall be free of cracks, floating rust and dents and burrs affecting the use.
DIN127 spring pad marking method
DIN127 spring pad marking example:
Marking of standard spring washer with thread inner diameter of 16, material of 65Mn spring steel and surface oxidation:

• Spring washer DIN127-B 16

Marking of heavy spring washer with thread inner diameter of 16, material of SUS304 stainless steel and no surface treatment:

• SUS304 spring washer DIN127-A 16

Application of DIN127 spring pad
DIN127 standard elastic pad is mainly used to prevent looseness. It is used to prevent looseness by using the elasticity of the elastic pad after locking under the condition of small vibration. Of course, the anti loosening effect of the spring pad is certainly not as good as that of the double nut, so the double nut is mostly used in the occasions with large vibration.
The locking effect of spring washer is general, and the important parts shall be used or not used as much as possible, and the self-locking structure shall be adopted. For the spring washer used for high-speed tightening (pneumatic or electric), it is best to use the washer with surface phosphating treatment to improve its wear reduction performance, otherwise it is easy to burn or open the mouth due to friction and heating, and even damage the surface of the connected parts. For thin plate joints, spring washer structure shall not be used.
The function of spring pad is realized by its elasticity and oblique friction. It is mainly used to prevent the automatic loosening of nuts or bolts in mechanical design and production. It is widely used to prevent the loosening of fasteners at the joints that are often disassembled. Spring pads are not used alone, but are generally used in combination.

GB93 spring washer standard

GB93 spring washer standard is GB93-87 updated by China in 1987, which specifies standard spring washer with specification of 2-48mm.
GB93 standard spring washer drawing:

Gb93 specifications and standard parameters of spring pad:

Major diameter of thread	d		s(b)			h
	min	max	Nominal	min	max	min	max
2	2.1	2.35	0.5	0.42	0.58	1	1.25
2.5	2.6	2.85	0.65	0.57	0.73	1.3	1.63
3	3.1	3.4	0.8	0.7	0.9	1.6	2
4	4.1	4.4	1.1	1	1.2	2.2	2.75
5	5.1	5.4	1.3	1.2	1.4	2.6	3.25
6	6.1	6.68	1.6	1.5	1.7	3.2	4
8	8.1	8.68	2.1	2	2.2	4.2	5.25
10	10.2	10.9	2.6	2.45	2.75	5.2	6.5
12	12.2	12.9	3.1	2.95	3.25	6.2	7.75
14	14.2	14.9	3.6	3.4	3.8	7.2	9
16	16.2	16.9	4.1	3.9	4.3	8.2	10.25
18	18.2	19.04	4.5	4.3	4.7	9	11.25
20	20.2	21.04	5	4.8	5.2	0	12.5
22	22.5	23.34	5.5	5.3	5.7	11	13.75
24	24.5	25.5	6	5.8	6.2	12	15
27	27.5	28.5	6.8	6.5	7.1	13.6	17
30	30.5	31.5	7.5	7.2	7.8	15	18.75
33	33.5	34.7	8.5	8.2	8.8	17	21.25
36	36.5	37.7	9	8.7	9.3	18	22.5
39	39.5	40.7	10	9.7	10.3	20	25
42	42.5	43.7	10.5	10.2	10.8	21	26.25
45	45.5	46.7	11	10.7	11.3	22	27.5
48	48.5	49.7	12	11.7	12.3	24	30

GB93 spring pad material
GB93 spring pad is divided into spring steel and stainless steel according to material. 65Mn spring steel or 70 spring steel and 3Cr13 stainless steel are usually used, and stainless steel SUS304 or SUS316 can also be used.
GB93 elastic pad material, heat treatment and surface treatment standards are as follows:

Material			Heat treatment	Surface treatment
Type	Brand	Standard No
Spring steel	65Mn	GB1222、GB5222	Quenching and tempering HRC 42~50	Oxidation, phosphating, galvanizing and passivation
	70
	60Si2Mn
Stainless Steel	3Cr13	GB1220	–	–
	1Cr18Ni9Ti
Copper and alloy	QSi3-1	GB4431	≥HB90	–

Note: the spring pad must be treated with hydrogen displacement immediately after galvanizing. The hardness of heat treatment is only for reference of production process.
GB93 marking method of spring pad
GB93 spring pad marking example:
Marking of standard spring washer with thread inner diameter of 16, material of 65Mn spring steel and surface oxidation:

• Spring washer GB93-16
• GB93 performance of spring pad

Elasticity: GB93 standard spring washer shall be loaded continuously for 3 times according to the specified test load, and then its free height shall be measured. The free height after the test shall not be less than 1.67s nominal height. The elasticity of stainless steel and copper gaskets shall be agreed by the supplier and the buyer.
The test load is specified in the following table:

Specifications/mm	2	2.5	3	4	5	6	8	10	12	14	16	18
Test load/N	700	1160	1760	3050	5050	7050	12900	20500	30000	41300	56300	69000

Specifications/mm	20	22	24	27	30	33	36	39	42	45	48
Test load/N	88000	110000	127000	167000	204000	255000	298000	343000	394000	457000	518000

Toughness: clamp the washer between the vice and the wrench so that the distance between the vice and the wrench is equal to one-half of the outer diameter of the washer. When slowly twisting the wrench clockwise for 90 degrees or 45 degrees, visually inspect the washer surface and continue to twist until it is broken. Visually inspect the section. The spring steel washer shall be twisted to 90 degrees, and the stainless steel and copper washer shall be twisted to 45 degrees without fracture. When it is twisted, the section shall be smooth.

Hydrogen embrittlement resistance: the gasket shall be separated by a flat pad, threaded on the test bar for compression, and reach the test load specified in the table above. It shall be placed for more than 48h and then loosened. The gasket surface shall be visually inspected and shall not be broken after the test.
Surface defects: the gasket surface shall be free of cracks, floating rust and dents and burrs affecting the use.
Knurling: the outer surface of the washer is allowed to have rolled patterns.
Application of gb93 spring pad
Gb93 spring pad can increase the preload and prevent looseness. Its function is realized by its elasticity and oblique friction. It is generally used in occasions with vibration, pulse and large fluctuation of medium temperature.
As mentioned above, spring pad is a common fastener in mechanical devices and equipment. It is widely used at the joints that are often disassembled to prevent the loosening of fasteners.

As shown in the figure, the spring washer is installed under the nut to prevent the nut from loosening, which is described in the national standard. After the nut is tightened, the elastic reaction force generated by flattening the cushion ring compresses the screwed threads axially. At the same time, the tip of the inclined mouth of the washer also has a loosening effect against the supporting surface of the nut and the connected piece.

Purpose of spring washer

The ideal installation method is to flatten as much as possible. The closer to the flattening state, the faster the tensioning torque increases. The appropriate bolt tension can be obtained without a torque wrench.
The spring washer is mainly used to prevent looseness. The flat washer has no loosening function, that is, the flat washer only increases the contact area, and the spring washer can prevent looseness. For example, the bolt connecting the motor and the base generally needs a spring washer, because the motor vibrates, and if there is no spring washer, the nut will loosen. Generally, fasteners on equipment with vibration are equipped with spring washers, and flat washers are generally not required on flanges. Whether to add a spring washer on the flange is related to the medium flowing through the pipeline. If it is easy to produce pulses, it is best to add a spring washer, as well as high-speed fluid. The caliber changes frequently. Don’t generalize.
On some valves, the packing box gland flange needs to be added with spring washer. In short, the flat washer is to increase the fastening contact area; Spring pad is used in places with vibration to prevent looseness; Fasten PVC flange without spring washer.
If you know that the main function of the spring washer is to prevent looseness, what are the specific service conditions of the spring washer?
The service conditions of spring washer are as follows: for the application of spring washer, the following four standards can be applied: standard spring washer (GB93-1987), light spring washer, (GB859-1987) and heavy spring washer (GB7244-1987). Purpose of spring washer: it is installed under the nut to prevent the nut from loosening. It is stated in national standards. Hexagon slotted nut is specially used with the bolt with hole at the end of the screw, so as to insert the cotter pin from the groove of the nut into the hole of the screw and prevent the nut from loosening automatically. It is mainly used in occasions with vibration load or alternating load.
Let’s give you a simple example to illustrate the application of spring washer in practical use:

This one in the picture is my first screw assembly, which is called hexagon socket bolt assembly.
This kind of bolt is a common furniture fastening hardware connector. Moreover, it is an important fastener, which is usually used for fixing the legs of a table. The rigorous hardware connection is usually shown in the figure below. When used with the cross bar nut, the spring gasket should be used.
Because once the bolts and nuts are tightened, there is a gap in the middle, and the furniture will inevitably shake after long-term use, which is likely to cause the screws to loosen.
Besides! Wood will be cold stretched and hot shrunk, and the main function of spring washer is to give buffer space. In terms of design idea, the spring washer (also known as spring washer) has pre tension and will rebound after being compressed.
In practical use, due to the characteristics of the thread, the nut is easy to rotate along the direction of the screw after tightening, resulting in the loosening of the nut.
Spring washers appeared early to solve this problem. Due to the pre tension of the spring washer, after the nut compresses the spring washer, under the action of the pre tension, the triangular buckle in the nut and one side of the triangular buckle of the bolt will stick closely together. Under the action of friction, the nut will no longer be loose.
The ordinary washer (also known as round hole gasket or flat gasket or ordinary gasket) is a support under the pre tension of the spring washer, which increases the pressing area of the pre tension of the spring washer.

Classification of spring washers

Washers are divided into: flat washer – grade C, large washer – grade A and C, extra large washer – grade C, small washer – grade A, flat washer – grade A, flat washer – chamfered – grade A, high-strength washer for steel structure, spherical washer, conical washer, square bevel washer for I-beam, square bevel washer for channel steel, standard tension spring washer, light tension spring washer, heavy tension spring washer, internal tooth lock washer Internal serrated lock washer, external serrated lock washer, external serrated lock washer, single lug stop washer, double lug stop washer, external tongue stop washer and stop washer for round nut.
Flat washers are commonly used in connectors. One is soft and the other is hard and brittle. Its main function is to increase the touch area, relax the pressure and avoid crushing the soft. The fundamental function of the tension spring of the tension spring washer is to give a force to the nut after the nut is tightened to increase the friction between the nut and the bolt. The material is 65Mn (tension spring steel), the heat treatment hardness is hrc44 ~ 51hrc, and the surface is oxidized.
Spring washer and snap spring are elastic cushions or clips.
Lock washer
Lock washer a washer that prevents bolts from loosening. The working principle of the lock washer is very simple. It consists of two washers. The outer side is with radial convex surface, while the inner side is oblique tooth surface. During installation, the inner oblique tooth surfaces are opposite, and the outer radial convex surface is in engagement with the touch surfaces at both ends. When the connector is oscillated and the bolt tends to loosen, it is only allowed to allow the relative dislocation between the inner oblique tooth surfaces of the two washers to produce lifting tension, and then reach 100% locking.
Case description
During steel structure construction, tension spring washer will not be used for high-strength bolts, but spring washer will be used for ordinary bolts. Is that right? Why?
Pretension shall be applied to high-strength bolts (friction type), and it is unfavorable to apply pretension after adding spring washer; The friction generated by the high-strength bolt under the pre tightening torque is enough to prevent loosening, so no additional measures are required to prevent loosening. Therefore, spring washers should not be added to high-strength bolts.
Ordinary bolt: it is necessary to ensure the tension of the bolt to prevent the bolt from loosening. A spring washer is added between the connecting plate and the nut to prevent looseness. After the preload is applied to the nut, the washer is flattened to produce an elastic reaction force, which compresses the screw threads and increases the friction to prevent looseness. However, due to uneven elasticity, the vibration and impact load during operation makes the anti loosening effect of the gasket very poor. Generally used for less important connections.
According to the performance grade of spring washer, the material is also different.

• For 100hv grade, ST12, ST13, Q235, Q215, Q195, etc. can be selected, and the surface hardness can reach about 110hv;
• For 140hv grade, 08F, 08Al, 10, 10F, etc. can be selected, and the surface hardness can reach about 140hv;
• For 200hv and 300hv grades, 45, 50, 60, 70 steel or 65Mn steel shall be selected, which can meet the technical requirements of 200 ~ 300hv and 300 ~ 400hv through heat treatment, quenching and tempering.

According to the standard, spring washers of 100hv and 140hv can be made of low carbon steel. General enterprises mostly use Baosteel materials when selecting materials, which is convenient for cold stamping.

Other categories

Inner tooth elastic washer, outer tooth elastic washer
There are many sharp elastic warping teeth on the circumference, which are stabbed and pressed on the bearing surface to prevent the loosening of fasteners. The internal tooth elastic washer is used under the screw head with small head size; External tooth elastic washers are mostly used under bolt heads and nuts. The elastic washer with teeth is smaller than the ordinary spring washer, and the fastener is stressed evenly and reliable to prevent loosening, but it is not suitable for frequent disassembly.
Wave Spring Washers:
National standard: GB/T 7246-1987
Corrugated washer is divided into WG type, WL type and wn type.
Type WG corrugated washer:
WG corrugated washer is an open elastic washer, which can usually be installed in a small space, such as applying prestress to the bearing, reducing the noise of bearing operation and improving the operation accuracy and stability of the bearing. In addition, there are a large number of Applied Materials in electronic and electrical appliances, such as carbon steel, stainless steel, copper alloy, etc.
WL type corrugated washer:
WL corrugated washer is a lap type elastic washer, which can usually be installed in a small space, such as applying prestress to the bearing, reducing the noise of bearing operation and improving the operation accuracy and stability of the bearing. In addition, it also has a large number of applications in electronic and electrical appliances. Materials include carbon steel, stainless steel, copper alloy, etc.
Wn type corrugated washer:
Wn type corrugated washer is a multi-layer wave crest overlapping elastic washer. Compared with WL type, this series is composed of multi-layer materials. Therefore, the K value curve under the same compression stroke is smoother than WL type, which is suitable for the case where the elastic force is large and the elastic force release throughout the working stroke is required to be uniform. The materials used are carbon steel, stainless steel, copper alloy, etc.
Belleville spring washer
Belleville spring washer, also known as Belleville spring washer, was invented by Belleville, France. Din6796 disc spring washer (HDS Series) is a lock washer designed for bolt and screw connection. It is designed and manufactured according to DIN 6796 and is used for the connection of medium or high strength bolts and screws. The large support load and elastic recovery make HDS series very effective. The bolt tension can withstand the relaxation caused by the following reasons: wear, creep, relaxation, thermal expansion, contraction of vulnerable parts, or compression of seals. HDS series increases the elasticity of the screw several times. It can effectively replace the ordinary spring washer, but it is not suitable for the combination of lock washer and flat washer. Because HDS series is a disc spring that can be split or stacked. The combination of involution mode can increase the deformation of disc spring group, and the combination of superposition mode can increase the spring force of disc spring group. The ideal installation method is to flatten as much as possible. The closer to the flattening state, the faster the tensioning torque increases. The appropriate bolt tension can be obtained without a torque wrench.

How to install the spring washer

first. The physical size and subsequent workload are considered. Scale is the first problem because you need to know the outside diameter, hole size and thickness. After these factors are known, you can specify the rated spring washer that will be placed on it through your equipment and the load of bolts and nuts. Spring washers made of different materials such as stainless steel, nickel alloy steel and copper alloy are also available.
Secondly, consider the gasket type. Types of spring washers several different types of spring washers exist. They are washers, which is a round spring compacted to a disk shape before hardening and tempering; Corrugated washer, which is a wavy, flat disc; Conical washer, which is designed as a high bearing washer; Bent washer, which is used to provide coiling end play, also known as axial clearance, in assembly; Constant force washers, which are adjustable gaskets; Or a finger washer having a finger around the outer diameter, which is designed to remove some load from the inner diameter of the washing machine and place it on the outside.
Finally, the spring washer is installed. The spring washer is installed in an assembly in the same way that the regular flat washer is used; The washer component is under the nut during assembly and the nut is tightened to a specified torque. This preload spring washer to its correct load rating.

Difference between gasket and washer

What is the difference between metal graphite spiral wound gasket and graphite gasket?

1. Different materials
Metal graphite spiral wound gasket: the metal graphite spiral wound gasket is the gasket with the best resilience among the semi-metal sealing gaskets. It is alternately wound by V-shaped or W-shaped thin steel belt and various fillers. Its structural density can be made according to different locking force requirements, and its maximum compression is controlled by using internal and external steel rings. The surface accuracy of the flange sealing surface contacted by the gasket is not high.
Graphite gasket: the graphite gasket is cut or stamped from pure graphite plate or metal (toothed plate, flat plate, mesh) reinforced graphite plate.
2. Different application scope
Metal graphite spiral wound gasket: sealing of flange joints such as pipelines, valves, pressure vessels, condensers, heat exchangers, towers, manholes and handholes in petroleum, chemical industry, metallurgy, electric power, shipbuilding, machinery and other industries.
Graphite gasket: used for various industrial pipe flanges, heat exchangers, valve covers, etc., as well as special shape flanges on liquid level gauges and water levels.
3. Different characteristics
Metal graphite spiral wound gasket: the gasket with the best resilience among the semi-metal sealing gaskets.
Graphite gasket: the sealing performance of flexible graphite gasket remains almost unchanged in the range from extremely low temperature to 400 ℃. Flexible graphite gasket has excellent chemical resistance to almost all liquids (except strong oxidizing acid). Due to small cold deformation and ductility, too tight installation has no impact on flexible graphite gasket.
Is there any difference between bolt flat gasket and gasket
The spring gasket is used to prevent looseness, and the flat gasket has no loosening function.
That is, the flat pad only increases the contact area, and the spring pad can prevent looseness. For example, the bolt connecting the motor and the base generally needs a spring pad, because the motor vibrates, and if there is no spring pad, the nut will loosen.
Generally, fasteners on equipment with vibration are equipped with spring gaskets, and gaskets are generally not required on flanges. Whether to add spring gasket on the flange is related to the medium flowing through the pipeline. If it is easy to produce pulse, it is best to add spring gasket, as well as high-speed fluid, and the caliber changes frequently.
On some valves, the packing box gland flange needs to be added with spring gasket. In short, the flat pad is to increase the fastening contact area; Spring pad is used in places with vibration to prevent looseness; Fasten PVC flange without spring gasket.

Difference between silicone gasket and PTFE gasket

The two have different characteristics:
1. Characteristics of silica gel gasket: it has certain tension, flexibility, excellent insulation, pressure resistance, high and low temperature resistance, stable chemical properties, environmental protection and safety, and no odor. Food grade silica gel gasket is non-toxic and tasteless, insoluble in water and any solvent. It is a high activity green product.
2. Features of PTFE gasket: this material product has the characteristics of acid resistance, alkali resistance, high temperature resistance and resistance to various organic solvents.
They are used for different purposes:
1. Application of silicone gasket: it is widely used in plexiglass, glass crafts, display rack, household appliances, furniture products, hardware accessories, transparent plastic products, etc.
2. Application of PTFE gasket: it is widely used in chemical and pharmaceutical industry. It is widely used in petroleum, chemical, pharmaceutical, electric power and iron and steel industries. Suitable media include water, oil, acid solution, alkali solution and almost all chemical components.
The two functions are different:
1. Function of silica gel gasket: the transparent silica gel gasket has beautiful appearance, shockproof, anti-skid, anti-collision and scratch prevention functions, and has high transparency.
2. Function of PTFE gasket: good mechanical toughness; The elongation of 5% can be maintained even if the temperature drops to – 196 ℃. For most chemicals and solvents, it is inert and resistant to strong acids, bases, aqua regia and various organic solvents.
Differences of several words of washer/gasket in Japanese

• Gasket = means [gas tight washer, sealing washer] and has the function of “sealing”.
• ライナー (liner) = generally refers to [adjusting gasket], which is a square and long strip-shaped sheet used to adjust the height.
• ワッシャャワッシャシャワッシャシシャワッシャざがねねねワシシャ = flat washer; ば seat gold = spring washer.
• スペサー (spacer) = [gasket, partition], especially refers to “insulating basin” in gas insulated fully enclosed switchgear.
• シム (shim) = [shim, gasket, spacer], which is similar to the purpose of ライナー, but the appellation is different according to the specific products and materials.

What is the difference between spring washer and metal washer and gasket

The spring washer is installed under the nut to prevent the nut from loosening.
Metal gasket is a kind of mechanical part that works by elasticity. Generally made of spring steel. It is used to control the movement of mechanical parts, mitigate impact or vibration, store energy, measure the size of force, etc. it is widely used in machines and instruments.
Gasket is a mechanical seal between two objects, usually to prevent pressure leakage between two objects. It is also a loophole (usually in the middle) in the thin plate (usually circular) and is usually a threaded fastener for distributing the load.

Is the bolt flat or spring washer

How to select a flat pad?

The flat pad is used as a part to prevent the bolt and nut from locking. Where fasteners are used, flat pads will be used. How to choose a suitable flat pad? Flat washer is a kind of flat washer, which is mainly used to increase and fasten the contact area between screws and some large equipment. When using flat washer, it is often suitable for nuts and nuts to cooperate with each other. When storing flat washer, it must have necessary important characteristics within the most effective sealing time:

• 1. In the case of bad environment, the flat gasket should be sealed. When a certain temperature and pressure is working, it is not easy to leak.
• 2. When the flat gasket is connected with the contact surface, it is necessary to better ensure the tightness, just like the just good effect.
• 3. When the gasket receives pressure, under the influence of temperature, the anti wrinkle ability should be better, otherwise the screw will be damaged and hard gas leakage will occur.
• 4. Do not get infected when using flat pads.
• 5. The flat pad can be disassembled well, which is the greatest function of selecting the flat pad.
• 6. Remember to ensure that the flat pad can be used normally at a relative temperature.

In order to better use the flat pad, when selecting the flat pad, try to select the flat pad dipped with anti-corrosion and anti rust materials, which not only saves time and labor, but also plays a good role.
When used with bolts and nuts, the selection criteria of flat gasket are as follows:

• 1. When selecting gasket materials, attention should be paid to the electrochemical corrosion of different metals. The material of the flat pad is generally the same as that of the connected parts, usually steel, alloy steel, stainless steel, aluminum alloy, etc. Copper and copper alloy can be selected when there are conductive requirements.
• 2. The inner diameter of the flat pad shall be selected according to the larger diameter of the thread or screw. The connected material shall be soft (such as composite material) or matched with the spring washer, and the larger outer diameter shall be selected.
• 3. When the w washer is placed on the bolt or screw head, in order to avoid the interference between the fillet under the head and the washer, the flat washer with inner hole chamfer can be selected.
• 4. Steel washers shall be used for important bolts with large diameter or to increase the extrusion resistance. Steel washer shall be used for tension bolt or tension shear composite bolt connection.
• 5. Special gaskets shall be used for special requirements. Copper gaskets can be used for conductive parts; Available sealing gaskets with air tightness requirements.

Function of flat pad:

• 1. Increase the contact area between the screw and the machine.
• 2. Eliminate the damage to the machine surface caused by the spring pad when removing the screw. When in use, it must be a spring pad a flat pad, the flat pad is next to the machine surface, and the spring pad is between the flat pad and the nut. The flat pad is used to increase the force bearing surface of the screw. In order to prevent the screw from loosening, the spring pad plays a certain buffer protection role when stressed. Although the flat pad can be used as a sacrificial pad.
• 3. But it is often used as a supplementary pad or flat pressing pad.

Advantage:

• ① By increasing the contact area, the parts can be protected from damage;
• ② By increasing the contact area, the pressure between the nut and the equipment is reduced, so as to play a protective role.

Disadvantages:

• ① The flat washer can not play the role of earthquake resistance;
• ② The flat washer also has no locking effect.

Spring pad
Function of spring pad:

• 1. The function of the spring washer is that after tightening the nut, the spring washer gives the nut an elastic force and butts the nut so that it is not easy to fall off. The basic function of the spring is to give a force to the nut after the nut is tightened to increase the friction between the nut and the bolt.
• 2. Generally, flat pads are not used for spring pads (flat pads and spring pads are considered only when the surfaces of fasteners and mounting surfaces are to be protected).
• 3. Flat pads are generally used in connectors. One is soft and the other is hard and brittle. Its main function is to increase the contact area, disperse the pressure and prevent crushing the soft ones.

Advantage:

• ① The spring washer has good anti loosening effect;
• ② Spring washer has good seismic effect;
• ③ Low manufacturing cost;
• ④ Easy to install.

Disadvantages:
The spring washer is greatly affected by the material and process. If the material is not good, the heat treatment is not grasped, or other processes are not done in place, it is easy to crack. Therefore, we must choose a reliable manufacturer.

When to use flat pads and spring pads?

• 1. Generally, the flat pad can be used only when the load is relatively small and does not bear the vibration load.
• 2. In case of large load and bearing vibration load, flat pad and elastic pad must be combined.
• 3. Spring washers are basically not used alone, but in combination.

In the actual use process, due to the different emphasis of flat washer and spring washer, they are used together in many occasions. In this way, they can protect parts, prevent nut loosening and reduce vibration at the same time. It is a great choice.

Difference between flat washer and spring washer

The spring washer can prevent looseness and increase the preload, while the flat washer does not. The flat washer can be used to increase the fastening contact area, prevent the friction between the bolt and the workpiece, protect the surface of the connector and prevent the surface of the workpiece from being scratched when the bolt and nut are tightened.

However, some important connections, such as those that mainly rely on compression to generate friction to transmit power, can not use spring pads. If they are used to reduce the connection rigidity, it is easy to have accidents. Spring washers may not be used. When the strength of the connected part is low, the flat pad or flange bolt shall be used to increase the contact area. When there is vibration, pulse and large fluctuation of medium temperature, the spring pad must be used.
Generally, fasteners on equipment with vibration are equipped with spring gaskets, and gaskets are generally not required on flanges. Whether to add spring gasket on the flange is related to the medium flowing through the pipeline. If it is easy to produce pulse, it is best to add spring gasket, as well as high-speed fluid, and the caliber changes frequently. Don’t generalize.
On some valves, the packing box gland flange needs to be added with spring gasket. In short, the flat pad is to increase the fastening contact area; Spring pad is used in places with vibration to prevent looseness; Fasten PVC flange without spring gasket.
Cause of hydrogen embrittlement fracture of spring washer opening expanding ring:

1. The expansion of the spring washer is generally not the problem of the spring washer itself.
2. The spring washer with expansion ring must be subjected to a radial outward tension, which originates from the tightening axial force generated by the tightening torque.
3. The outer chamfer of the nut bearing surface produces a radial component of the axial clamping force, resulting in the expansion of the opening of the spring washer. The smaller the chamfer diameter, the greater the possibility of ring expansion.
4. Adding a flat washer between the nut and the spring washer helps to slow down or prevent the expansion of the ring, but the flat washer is too thin or too soft to prevent the expansion of the ring.
5. The hydrogen embrittlement fracture of spring washer is generally caused by unreasonable heat treatment process and the failure to conduct hydrogen treatment in time after zinc plating.

A large number of experiments and long-term practical experience confirm the above analysis.

Source: China Spring Washer Manufacturer – Yaang Pipe Industry Co., Limited (www.pipelinedubai.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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Please notice that you might be interested in the other technical articles we’ve published:

• What is a washer
• What is a sealing ring
• What are Flange Gaskets