What is a washer?

What is a washer?

Washer is a part which is usually used to pad between the connecting piece and the nut. Its purpose is to protect the surface of the connected piece from being scratched by the nut, to disperse the pressure of the nut on the connected piece, and to reduce the separation caused by vibration.

Washers are usually metal or plastic, usually flat metal rings. Since the torque is applied after indentation to prevent the loss of preload, hardened steel washers are required in special cases. Especially by insulating steel screws from aluminum surfaces.
Taps (or taps, or valves) used in rubber or fiber gaskets to stop the flow of water are sometimes referred to as gaskets; however, although they may look similar, washers and gaskets are usually designed for different functions.

The difference between gaskets and washers

A washer is a thin plate (typically disk-shaped, but sometimes square) with a hole (typically in the middle) that is normally used to distribute the load of a threaded fastener, such as a bolt or nut. Other uses are as a spacer, spring (Belleville washer, wave washer), wear pad, preload indicating device, locking device, and to reduce vibration (rubber washer). Washers often have an outer diameter (OD) about twice their inner diameter (ID), but this can vary quite widely.
Washers are usually metal or plastic. High-quality bolted joints require hardened steel washers to prevent the loss of pre-load due to brinelling after the torque is applied. Washers are also important for preventing galvanic corrosion, particularly by insulating steel screws from aluminium surfaces. They may also be used in rotating applications, as a bearing. A thrust washer is used when a rolling element bearing is not needed either from a cost-performance perspective or due to space restraints. Coatings can be used in attempt to reduce wear and friction either by hardening their surface, or providing a solid lubricant (i.e. a self-lubricating surface).
A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression.
Gaskets allow for “less-than-perfect” mating surfaces on machine parts where they can fill irregularities. Gaskets are commonly produced by cutting from sheet materials.
Gaskets for specific applications, such as high pressure steam systems, may contain asbestos. However, due to health hazards associated with asbestos exposure, non-asbestos gasket materials are used when practical.
It is usually desirable that the gasket be made from a material that is to some degree yielding such that it is able to deform and tightly fill the space it is designed for, including any slight irregularities. A few gaskets require an application of sealant directly to the gasket surface to function properly.
Some (piping) gaskets are made entirely of metal and rely on a seating surface to accomplish the seal; the metal’s own spring characteristics are utilized (up to but not passing σy, the material’s yield strength). This is typical of some “ring joints” (RTJ) or some other metal gasket systems. These joints are known as R-con and E-con compressive type joints.

Types of Washers

A washer is a piece of hardware that evenly distributes the force of a screw or nut. Washers can also relieve friction, prevent corrosion or leakage, maintain tension and serve as a spacer. Their wide range of applications makes them a necessity in most construction projects; however, choosing the right type of washer for a project can be more complicated than it seems. This guide will list and describe the many types of washers and their recommended purposes. 

  • Plain washer
  • Spring washer

What is a plain washer?

Plain washer (or “flat washer”)

100px Plain washer1 - What is a washer?

A flat annulus or ring, often of metal, used to spread the load of a screwed fastening. Additionally, a plain washer may be used when the hole is a larger diameter than the fixing nut.

Flat washers come in various sizes for one screw diameter, from tiny to extra-large.

12fa1ebba9bdd64fa82517dd9c027c8e - What is a washer?

The main role of flat washers is to increase the size of a screw’s bearing surface area, and reduce the surface pressure applied on the fastened object. Looseness can result when the bearing surface sinks under the surface pressure, so using a flat washer to reduce the surface pressure is very effective. This is especially crucial if the contact area between a screw’s bearing surface and the object being fastened is small when fastening to a slot, for instance, or if the object being fastened is made of soft material such as aluminum or resin.

60a742ad06c45c3537a882855f531f02 - What is a washer?

Incidentally, since flat washers are basically manufactured by pressing, one side has rounded corners and one side has burrs, as shown in the figure below.

460134404401b2af32f76027a1e833ab - What is a washer?

There is no fixed rule about which side goes up and which goes down, but given the issue of bearing surface pressure mentioned above, it’s more effective to put the burred side facing down. That said, since the burrs could mark the surface of the fastened object during tightening, it would be better to put the rounded side down if you want to avoid plating peeling.

Flat washer is generally used to increase the contact area between parts. Its advantages and disadvantages are as follows:

Advantage:

  • ① By increasing the contact area, the parts can be protected from damage;
  • ② By increasing the contact area and reducing the pressure between the nut and the equipment, it can play a protective role.

Disadvantages:

  • ① The flat washer can’t resist earthquake;
  • ② The flat washer also has no locking effect.

List of sizes for flat washers regulated by JIS

Small size – Shape and dimensions of part grade A

Small size – Shape of part grade A

000637293f85a261a32d2e659248e1a5 - What is a washer?

Unit : mm

Nominal diameter of
plain washer*(Nominal diameter of
thread d) 
Inside diameter d1  Outside diameter d2  Thickness h 
Basic dimension
(Min.)
Max.  Basic dimension
(Max.)
Min. Basic Dimension  Max.  Min.
1.6    1.70   1.84   3.5   3.2  0.3  0.35  0.25
2   2.20   2.34   4.5   4.2  0.3  0.35  0.25
2.5   2.70   2.84   5.0   4.7  0.5  0.55  0.45
3   3.20   3.38   6.0   5.7  0.5  0.55  0.45
(3.5)   3.70   3.88   7.00   6.64  0.5  0.55  0.45
4   4.30   4.48   8.00   7.64  0.5  0.55  0.45
5   5.30   5.48   9.00   8.64  1  1.1  0.9
6   6.40   6.62 11.00 10.57  1.6  1.8  1.4
8   8.40   8.62 15.00 14.57  1.6  1.8  1.4
10 10.50 10.77 18.00 17.57  1.6  1.8  1.4
12 13.00 13.27 20.00 19.48  2  2.2  1.8
(14) 15.00 15.27 24.00 23.48  2.5  2.7  2.3
16 17.00 17.27 28.00 27.48  2.5  2.7  2.3
(18) 19.00 19.33 30.00 29.48  3  3.3  2.7
20 21.00 21.33 34.00 33.38  3  3.3  2.7
(22) 23.00 23.33 37.00 36.38  3  3.3  2.7
24 25.00 25.33 39.00 38.38  4  4.3  3.7
(27) 28.00 28.33 44.00 43.38  4  4.3  3.7
30 31.00 31.39 50.00 49.38  4  4.3  3.7
(33) 34.00 34.62 56.00 54.8  5  5.6  4.4
36 37.00 37.62 60.00 58.8  5  5.6  4.4

 Parenthesized nominal diameter of thread represents Choice 2.

Standard size – Part grade A and standard-sized chamfering*2 – Shape and dimensions of part grade A

Standard size – Shape of part grade A                                                            Standard-sized chamfering – Shape of part grade A

2713b8e1f5bc1b34a5b67841747996bf - What is a washer?

Unit : mm

Nominal diameter of
plain washer*1 (Nominal diameter of
thread d)
Inside diameter d1  Outside diameter d2  Thickness h 
Basic dimension
(Min.)
Max.  Basic dimension
(Max.)
Min.  Basic dimension Max.  Min. 
1.6    1.70   1.84   4.0   3.7 0.3 0.35 0.25
2   2.20   2.34   5.0   4.7 0.3 0.35 0.25
2.5   2.70   2.84   6.0   5.7 0.5 0.55 0.45
3   3.20   3.38   7.00   6.64 0.5 0.55 0.45
(3.5)   3.70   3.88   8.00   7.64 0.5 0.55 0.45
4   4.30   4.48   9.00   8.64 0.8 0.9 0.7
5   5.30   5.48 10.00   9.64 1 1.1 0.9
6   6.40   6.62 12.00 11.57 1.6 1.8 1.4
8   8.40   8.62 16.00 15.57 1.6 1.8 1.4
10 10.50 10.77 20.00 19.48 2 2.2 1.8
12 13.00 13.27 24.00 23.48 2.5 2.7 2.3
(14) 15.00 15.27 28.00 27.48 2.5 2.7 2.3
16 17.00 17.27 30.00 29.48 3 3.3 2.7
(18) 19.00 19.33 34.00 33.38 3 3.3 2.7
20 21.00 21.33 37.00 36.38 3 3.3 2.7
(22) 23.00 23.33 39.00 38.38 3 3.3 2.7
24 25.00 25.33 44.00 43.38 4 4.3 3.7
(27) 28.00 28.33 50.00 49.38 4 4.3 3.7
30 31.00 31.39 56.00 55.26 4 4.3 3.7
(33) 34.00 34.62 60.0 58.8 5 5.6 4.4
36 37.00 37.62 66.0 64.8 5 5.6 4.4

1  Parenthesized nominal diameter of thread represents Choice 2.
2  Standard-sized chamfering – Shall be specified for nominal diameter of thread 5 or above among applicable part grade A threads.

Standard size – Shape and dimensions of part grade C

Standard size – Shape of part grade C

8db18537e8cc1baae002115c254d6388 - What is a washer?

Unit : mm

Nominal diameter of
plain washer*
(Nominal diameter of
thread d)
Inside diameter d1  Outside diameter d2  Thickness h 
Basic dimension
(Min.)
Max.  Basic dimension
(Max.)
Min. Basic dimension Max.  Min.
1.6    1.80   2.05   4.00   3.25 0.3 0.4 0.2
2   2.40   2.65   5.00   4.25 0.3 0.4 0.2
2.5    2.90   3.15   6.00   5.25 0.5 0.6 0.4
3   3.4   3.7   7.0   6.1 0.5 0.6 0.4
(3.5)   3.9   4.2   8.0   7.1 0.5 0.6 0.4
4   4.5   4.8   9.0   8.1 0.8 1 0.6
5   5.5   5.8 10.0   9.1 1 1.2 0.8
6   6.60   6.96 12.0 10.9 1.6 1.9 1.3
8   9.00   9.36 16.0 14.9 1.6 1.9 1.3
10 11.00 11.43 20.0 18.7 2 2.3 1.7
12 13.50 13.93 24.0 22.7 2.5 2.8 2.2
(14) 15.50 15.93 28.0 26.7 2.5 2.8 2.2
16 17.50 17.93 30.0 28.7 3 3.6 2.4
(18) 20.00 20.52 34.0 32.4 3 3.6 2.4
20 22.00 22.52 37.0 35.4 3 3.6 2.4
(22) 24.00 24.52 39.0 37.4 3 3.6 2.4
24 26.00 26.52 44.0 42.4 4 4.6 3.4
(27) 30.00 30.52 50.0 48.4 4 4.6 3.4
30 33.00 33.62 56.0 54.1 4 4.6 3.4
(33) 36 37 60.0 58.1 5 6 4
36 39 40 66.0 64.1 5 6 4

Parenthesized nominal diameter of thread represents Choice 2.

Large size – Shape and dimensions of part grade A or C

Large size – Shape of part grade A                                                                             Large size – Shape of part grade C

2b2032fd8b457a8b232d6adb6d3ab14a - What is a washer?

Unit : mm

Nominal diameter of
plain washer*
(Nominal diameter of
thread d)
Inside diameter d1  Outside diameter d2  Thickness h
Basic dimension
(Min.)
Max.  Basic dimension
(Max.)
Min.  Basic dimension Max.  Min. 
Part grade Part grade Part grade Part grade Part grade Part grade Part grade
 A A and C  A and 
3   3.20   3.4   3.38   3.7     9.00     8.64     8.1 0.8 0.9 1.0 0.7 0.6
(3.5)    3.70   3.9   3.88   4.2   11.00   10.57     9.9 0.8 0.9 1.0 0.7 0.6
4   4.30   4.5   4.48   4.8   12.00   11.57   10.9 1 1.1 1.2 9 0.8
5   5.30   5.5   5.48   5.8   15.00   14.57   13.9 1 1.1 1.2 9 0.8
6   6.40   6.60   6.62   6.96   18.00   17.57   16.9 1.6 1.8 1.9 1.4 1.3
8   8.40   9.00   8.62   9.36   24.00   23.48   22.7 2 2.2 2.3 1.8 1.7
10 10.50 11.00 10.77 11.43   30.00   29.48   28.7 2.5 2.7 2.8 2.3 2.2
12 13.00 13.50 13.27 13.93   37.00   36.38   35.4 3 3.3 3.6 2.7 2.4
(14) 15.00 15.50 15.27 15.93   44.00   43.38   42.4 3 3.3 3.6 2.7 2.4
16 17.00 17.50 17.27 17.93   50.00   49.38   48.4 3 3.3 3.6 2.7 2.4
(18) 19.00 20.00 19.33 20.52   56.00   55.26   54.1 4 4.3 4.6 3.7 3.4
20 21.00 22.00 21.33 22.52   60.00   59.26   58.1 4 4.3 4.6 3.7 3.4
(22) 23.00 24.00 23.52 24.84   66.0   64.8   64.1 5 5.6 6 4.4 4
24 25.00 26.00 25.52 26.84   72.0   70.8   70.1 5 5.6 6 4.4 4
(27) 30.00 30.00 30.52 30.84   85.0   83.6   82.8 6 6.6 7 5.4 5
30 33.00 33.00 33.62 34   92.0   90.6   89.8 6 6.6 7 5.4 5
(33) 36.00 36.00 36.62 37 105.0 103.6 102.8 6 6.6 7 5.4 5
36 39.00 39.00 39.62 40 110.0 108.6 107.8 8 9 9.2 7 6.8

Parenthesized nominal diameter of thread represents Choice 2.

Super-large size – Shape and dimensions of part grade C

Super-large size – Shape of part grade C

b273bc4e33e9f156a007994b007d7b1a - What is a washer?

Unit : mm

Nominal diameter of
plain washer*
(Nominal diameter of
thread d)
Inside diameter d1  Outside diameter d2  Thickness h 
Basic dimension
(Min.) 
Max.  Basic dimension
(Max.) 
Min.  Basic dimension Max.  Min. 
  5.5   5.8   18.0   16.9 2 2.3 1.7
  6.60   6.96   22.0   20.7 2 2.3 1.7
8   9.00   9.36   28.0   26.7 3 3.6 2.4
10 11.00 11.43   34.0   32.4 3 3.6 2.4
12 13.50 13.93   44.0   42.4 4 4.6 3.4
(14) 15.50 15.93   50.0   48.4 4 4.6 3.4
16 17.5 18.2   56.0   54.1 5 6 4
(18) 20.00 20.84   60.0   58.1 5 6 4
20 22.00 22.84   72.0   70.1 6 7 5
(22) 24.00 24.84   80.0   78.1 6 7 5
24 26.00 26.84   85.0   82.8 6 7 5
(27) 30.00 30.84   98.0   95.8 6 7 5
30 33 34 105.0 102.8 6 7 5
(33) 36 37 115.0 112.8 8 9.2 6.8
36 39 40 125.0 122.5 8 9.2 6.8

 Parenthesized nominal diameter of thread represents Choice 2.

What are spring washers?

100px Grower01 - What is a washer?

Spring washers are a left hand helix and allow the thread to be tightened in a right hand direction only, i.e. a clockwise direction. When a left hand turning motion is applied, the raised edge bites into the underside of the bolt or nut and the part that it is bolted to, thus resisting turning. Therefore, spring washers are ineffective on left hand threads and hardened surfaces[citation needed]. Also, they are not to be used in conjunction with a flat washer under the spring washer, as this isolates the spring washer from biting into the component that will resist turning.
The use and effectiveness of spring lock washers has been in debate of late, with some publications[13][who?] advising against their use on the grounds that, when tight, the washer is flat against the substrate and gives no more resistance to rotation than a normal washer at the same torque. NASA researchers have gone as far as to say “In summary, a lockwasher of this type is useless for locking.” However, a spring washer will continue to hold the bolt against the substrate and maintain friction when loosened slightly, whereas a plain washer will not.
The benefit of spring lock washers lies in the trapezoidal shape of the washer. When compressed to loads near the proof strength of the bolt, it will twist and flatten. This reduces the spring rate of the bolted joint which allows it to maintain more force under the same vibration levels. This prevents loosening.

The spring washer can play the role of locking by its own elastic force. Its advantages and disadvantages are as follows:

Advantage:

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

Disadvantages:

Spring washer is greatly affected by material and technology. If the material is not good, heat treatment is not good or other technology is not in place, it is easy to crack. Therefore, we must choose reliable manufacturers, such as our No. 1 product, whose quality is reliable!

List of sizes for spring washers regulated by JIS

Shape and dimensions of spring lock washers for general purpose (No.2) and for heavy load (No.3)

15f5a47d2ab4b5047da86ea512e43e9e - What is a washer?

Unit : mm

Type  Dimensions of spring lock washers for general purpose (No.2)  Dimensions of spring lock washers for heavy load (No.3) 
Nominal
Diameter  
Inside diameter d  Section size (Min.)  Outside
diameter
D (Max.) 
Inside diameter d  Section size Outside
diameter
D (Max.) 
Basic
Dimension
Allowance B  Breadth b  Thickness
t (1) 
Basic
Dimension
Allowance  Breadth b  Thickness
t (1) 
2.1 +0.25
  0
0.9 0.5 4.4
2.5 2.6 +0.3
  0
0.6 5.2
3 3.1 1.1 0.7 5.9
(3.5) 3.6 1.2 0.8 6.6
4 4.1 +0.4
  0
1.4  1 7.6
(4.5) 4.6 1.5 1.2 8.3
5 5.1 1.7 1.3 9.2
6 6.1 2.7 1.5 12.2 6.1 +0.4
  0
2.7 1.9 12.2
(7) 7.1 2.8 1.6 13.4 7.1 2.8 2.0 13.4
8 8.2 +0.5
  0
3.2 2 15.4 8.2 +0.5
  0
3.3 2.5 15.6
10 10.2 3.7 2.5 18.4 10.2 3.9 3.0 18.8
12 12.2 +0.6
  0
4.2 3 21.5 12.2 +0.6
  0
4.4 3.6 21.9
(14) 14.2 4.7 3.5 24.5 14.2 4.8 4.2 24.7
16 16.2 +0.8
  0
5.2 4 28 16.2 +0.8
  0
5.3 4.8 28.2
(18) 18.2 5.7 4.6 31 18.2 5.9 5.4 31.4
20 20.2 6.1 5.1 33.8 20.2 +1.0
  0
6.4 6.0 34.4
(22) 22.5 +1.0
  0
6.8 5.6 37.7 22.5 7.1 6.8 38.3
24 24.5 7.1 5.9 40.3 24.5 +1.2
  0
7.6 7.2 41.3
(27) 27.5 +1.2
  0
7.9 6.8 45.3 27.5 8.6 8.3 46.7
30 30.5 8.7 7.5 49.9
(33) 33.5 +1.4
  0
9.5 8.2 54.7
36 36.5 10.2 9 59.1
(39) 39.5 10.7 9.5 63.1

 

1cf348034707d01b9a93968370596d45 - What is a washer?

In which case T2-Tmust be 0.064b or lower. However, b shall be min. value specified in this table.  

Remark: Use of parenthesized nominal diameter of thread should be discouraged. 

The graph below shows the results from a Junker vibration test of a screw using both a spring washer and a flat washer. You can see that it is loosened and the axial force drops over time.

86c3044baaac5405c1c1594c7025b3cf - What is a washer?

And since looseness occurs with an NAS vibration test, too, it would seem that spring washers have no effect against looseness caused by vibration.

In the actual use process, due to the different emphases of flat washer and spring washer, they are used together in many occasions, which is a good choice to protect parts, prevent nuts from loosening and reduce vibration.

8a1e9dac0d1daf5ab3474fee0bce6d88 hd - What is a washer?

In terms of design idea, the spring washer (also called spring washer) has pretension, after being compressed, it will react. In practical use, due to the characteristics of the thread, it is easy for the nut to rotate along the direction of the thread after tightening, resulting in the loosening of the nut. In order to solve this problem, spring washers appeared in the early days. Spring washer has pretension. After the nut compresses the spring washer, under the action of pretension, the triangle bolt in the nut and one side of the triangle bolt are closely adhered together. Under the action of friction, the nut will no longer be loose. The ordinary washer (also known as circular hole washer or flat washer or ordinary washer) is a support under the pretension of spring washer, which increases the area of preload of spring washer. Generally speaking, spring washer and plain washer are used together, and it is unreasonable to use plain washer alone. Of course, it does not exclude the design and actual needs of individual uses. For example, when the plastic shell of electrical appliances is screwed with self tapping screws, the following individual ordinary washers are only used to increase the stress area.
As shown in the picture above, the plain washer and spring washer are usually used together. There are two reasons:

  • Spring washer has destructive force on the acting material, such as solid wood, which will damage the stressed surface, and ordinary washer plays a protective role;
  • Ordinary washer is usually larger than the diameter of spring washer, so it will increase the stress area at the same time, and the fastening is more stable. 

Source: China Washers 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.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@pipelinedubai.com

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

Summary
what is a washer - What is a washer?
Article Name
What is a washer?
Description
A washer is a thin plate (typically disk-shaped, but sometimes square) with a hole (typically in the middle) that is normally used to distribute the load of a threaded fastener, such as a bolt or nut.
Author
Publisher Name
www.pipelinedubai.com
Publisher Logo

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