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Introduction
This article takes an in depth look at metal washers and their use.
You will learn more about topics such as:
What is a Metal Washer
How Metal Washers are Made
Uses for Metal Washers
Metals Used to Make Metal Washers
Types of Metal Washers
And much more…
Chapter One – What is a Metal Washer?
A metal washer is a small flat piece of metal that has a hole in the center and is used as a spacer, a method for absorbing shock, or distributing the load of a fastener. The hole in the middle of a metal washer allows for a bolt or screw to pass through. There are several methods used to produce metal washers, each of which is designed to produce them with a sufficient amount of strength and stress resistance.
The manufacture of metal washers includes many different types of materials, with galvanized carbon steel and stainless steel being the most common. The variations in the metals used to produce metal washers and their many shapes have created a wide assortment of washer types, with plain, spring, and lock being the standard types. Under the three commonly used metal washers are several specialty washers designed to meet the needs of specific applications.
Chapter Two – Uses for Metal Washers
There are endless uses for metal washers with specialty ones being manufactured for unique and unusual applications. Metal washers are designed to distribute the load of a fastener such as a screw, bolt, nut, or another form of connecting fastener that securely fits.
Washers make it easier to loosen or remove a nut from a bolt and easily resecure it. There are many types of washers for home use as well as those that are produced for industrial applications.
Metal Washer Uses
Load Distribution
The main function of all washers is to distribute the load of a fastener when it is driven in or connected to a material. Fasteners without a washer tend to stress surfaces causing cracks, impressions, and other deformities. Metal washers protect against such damage by distributing and lessening the stress from the fastener by evenly distributing the load. Stress relief is not necessary for all materials except those that are soft such as wood.
Using as a Spacer
Another common use of metal washers is as spacers for fasteners that are longer than the depth of the hole into which they are being driven. When some fasteners are used, a space is left between the head of the fastener and the material’s surface. If a four inch bolt is connected to material that is three inches deep, there will be a one inch gap and the connection will not be secure. Inserting metal washers, as seen below, between the surface and the head of the bolt before it is connected fills the one inch empty space.
Sealing
Sealing washers are a special type of washer that has a layer of material bonded to the metal, such as neoprene. The strength of the metal washer and the sealing power of the material form a tight seal to prevent leaks and drips. Though sealing washers are very strong and resilient, they are also soft and smooth to prevent damage to the sealed surface. Sealing washers are an ideal tool for the sealing of bolt joints.
The securing of sealing metal washers has to be carefully, and precision completed since over tightening can cause leaks. The washer must be placed against the surface such that it is not convex or concave.
The bonding of the sealing material creates a corrosion resistant surface that cushions the bolt head and seals the joint. In addition to sealing leaks, sealing washers serve as a vibration dampening tool.
Using for Repair
A specific type of washer, referred to as a fender washer, is used for repairing connections when a hole has been damaged by rust or corrosion. The washer has a small hole with a very large outer diameter that can cover the hole but allow for a fastener to be attached.
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Chapter Three – How Metal Washers are Made
There are few limitations on the types of materials that can be used to produce washers. Though galvanized carbon steel and stainless steel are most commonly used, other metals such as aluminum and copper are also used. The choice of metal for metal washers has a great deal to do with how they will be used.
Specially designed hardened metal washers are used to maintain fastener tension under demanding or difficult conditions. Soft metals, such as aluminum and copper, are ideal for conditions where a washer is used for sealing as well as load distribution.
Making Metal Washers
Washers are made by the stamping process, which is completed on a power press. The washer form is determined by a die attached to the stamping or power press ram.
Metal Stamping
Metal stamping is a cold metal working process that uses a die to punch a form or shape from a flat piece of metal. Flat sheets of metal, blanks, are fed into the bolster plate where the ram comes down on it with great force to punch out the shape. The mechanism for a stamping machine can be mechanical with a flywheel or hydraulic.
Washer Dies
Washer dies are customized forms that are specifically designed for the manufacturing of washers. Since washers are a very small item, multiples are stamped or pressed from a single sheet of metal. Stamping is a fast and smooth process capable of producing large amounts of washers while ensuring the maximum use of the metal sheets.
Several types of dies are used to produce a variety of simple to complex products. The types of dies are simple, compound, progressive, transfer, combination, and multiple. For the manufacture of washers, compound dies are used.
In the compound die process, more than one operation takes place in a single stroke. In the case of washers, the outer edge and central hole are formed in one stroke. The die blanks and perforates the workpiece at a single workstation. The holes and shape of the washer are punched into the blank and moved up while the scrap moves down.
Gauge of Metals
The thickness of the washer is determined by the gauge of the metal, which is a factor in the amount of spacing the washer provides. The gauge method of determining thickness goes back to the middle of the first industrial revolution when there wasn’t any universal method for measuring thickness.
There is a different gauge chart for every form of metal since there isn’t any uniformity between the different gauges. Regardless of which chart is used, the higher the number, the thinner the metal will be.
The thickness of a washer also affects other factors such as rigidity, support, and damping capabilities.
The gauge chart below is for carbon steel.
Carbon Steel Gauge Chart
Ga No.
Hot Rolled, HR P&O, Cold Rolled
Galvanized/Galvannealed
Dec. Equiv.
Toler.RangeHR, P&O, CR
Lbs. per Sq. ft
Dec. Equiv.
Toler.Range
Lbs. per Sq. ft
4
.2242
.2332 .2152
9.375
5
.2092
.2182 .2002
8.750
6
1.943
.2033 .1853
8.125
7
.1793
.1873 .1713
7.500
8
.1644
.1724 .1564
6.875
.1681
.1771 .1591
7.031
9
.1495
.1575 .1415
6.250
.1532
.1622 .1442
6.406
10
.1345
.1425 .1265
.1405 .1285
5.625
.1382
.1472 .1292
5.156
11
.1196
.1276 .1116
.1256 .1136
5.000
1.233
.1323 .1143
5.156
12
.1046
.1126 .0966
.1106 .0986
4.375
.1084
.1174 .0994
4.531
13
.0897
.0967 .0827
.0947 .0847
3.750
.0934
.1014 .0854
3.906
14
.0747
.0817 .0677
.0797 .0697
3.125
0.785
.0865 .0705
3.281
15
.0673
.0733 .0613
.0723 .0623
2.813
.0710
.0770 .0650
2.969
16
.0598
.0648 .0538
.0648 .0548
2.500
.0635
.0695 .0575
2.656
Choosing Metals
The choice of metal for a washer affects its strength, corrosion resistance, brittleness, and cost. When choosing a washer, there are several additional factors to consider. To get optimum performance from a washer, it is important that it matches the material with which it will be used. Replacing a washer with a stronger, more durable one may seem ideal but can lead to damage to equipment or safety problems.
The most common metals used to produce washers are zinc plated steel and various grades of stainless steel. Though these two metals are normally used for their strength and corrosion resistance, softer metals such as copper and aluminum are used to meet the special needs of specific applications.
Chapter Four - Leading Metal Washer Machinery
There are many machines available to produce metal washers in the United States and Canada. These machines are essential in today's society as they enable efficient and precise mass production of metal washers, which are vital components used in various industries such as automotive, aerospace, construction, and appliances. We examine many of these leading machines and their special capabilities that have led to their success below.
AIDA DSF Series Stamping Presses
Manufacturer: AIDA Engineering, Ltd.
Characteristics: AIDA DSF Series Stamping Presses are well-regarded for their high precision, speed, and reliability. They can efficiently produce washers with consistent shapes and dimensions. The DSF series, in particular, offers advanced automation and servo control systems, allowing for quick setup and changeover, which boosts production efficiency.
Schuler MSP Series Mechanical Presses
Manufacturer: Schuler Group
Characteristics: Schuler MSP Series Mechanical Presses are known for their robust construction and high power output. They are often used for high-volume production of washers due to their fast cycling times and excellent repeatability. Their durability and low maintenance requirements contribute to their popularity.
Haas VF Series Vertical Machining Centers
Manufacturer: Haas Automation, Inc.
Characteristics: Haas VF Series Vertical Machining Centers offer versatility and precision in producing metal washers with complex designs. Haas VF Series Vertical Machining Centers are equipped with advanced features like high-speed spindles, rigid construction, and user-friendly controls. These attributes enable efficient machining of various materials, making them a favored choice for custom washer manufacturing.
Waterbury Farrel Four-Slide Machines
Manufacturer: Waterbury Farrel
Characteristics: These four-slide machines are specifically designed for efficient production of small to medium-sized washers and other intricate parts. They use a unique four-slide forming process that reduces material waste and allows for multiple operations in a single cycle. Waterbury Farrel's machines are highly regarded for their precision, reliability, and ease of operation.
EBU Umformtechnik Screw Machines
Manufacturer: EBU Umformtechnik GmbH
Characteristics: These screw machines, also known as cold formers or thread rolling machines, are widely used for the mass production of metal washers. EBU Umformtechnik's machines excel in cold forming processes, which involve material deformation at room temperature, resulting in higher material strength and improved surface finish of the washers. These machines are popular for their cost-effectiveness and high-speed production capabilities.
Please note that machine availability, popularity, and advancements can change over time. For the most current and accurate information, it's essential to consult manufacturers, industry experts, and up-to-date sources when considering the best machines for producing metal washers.
Chapter Five – Metals Used to Make Metal Washers
The wide assortment of washer configurations also includes a varied selection of metals. One of the required characteristics of metals for washers is that they are resilient, strong, and durable. In some cases, washers need to be pliable enough to form a seal and maintain a tight connection.
The selection of the proper metal is a crucial and essential part of the washer production process since the wrong metal can cause an application or operation to fail. Metals for washers are chosen in conjunction with the type of environment and conditions where they will be used.
Metals Used to Make Metal Washers
Stainless Steel
Stainless steel is a natural choice for the manufacture of washers due to its many positive properties. As a steel alloy with chromium, stainless steel does not rust or corrode. The various elements in stainless steel react with oxygen and moisture to produce a film that serves as a barrier against corrosion and other harmful substances. Stainless steel washers are used in the petrochemical industry, aerospace, and the auto industry.
Galvanized Steel
Galvanized steel is coated with zinc as a means of protection against corrosion. Hardened steel made by stamping is used to produce the initial washer shape before being coated with zinc. Galvanized steel washers have a rough, uneven surface and come in different colors. They are the ideal choice for marine applications since the zinc coating protects against the effects of salt water.
Aluminum Washers
Like stainless steel, aluminum has many characteristics and properties that make it an ideal metal for manufacturing washers. When aluminum is exposed to the air, it forms a layer of aluminum oxide that protects against corrosion. It has excellent thermal and electrical conducting properties that are far superior to other metals. Aluminum washers are widely used in applications that require heat dissipation.
Inconel Alloy
Inconel is an alloy that is made from nickel, chromium, and molybdenum alloys. It has superior strength at high temperatures with exceptional corrosion resistance. Inconel’s range of temperatures runs from cryogenic to 2200o F or 982o C. The alloy content of Inconel washers allows them to withstand severe and harsh conditions. The combination of nickel and chromium provides resistance to oxidizing chemicals, while the nickel and molybdenum are resistant to non oxidizing environments. Typical grades of Inconel used to produce washers are 600, 601, 625, 686, 718, and 725.
Inconel’s resistance to corrosion, temperature stability, toughness, and strength make it the first choice for washers used for chemical processing, aerospace applications, the marine industry, and oil and gas production.
Copper Washers
The main feature of copper that makes it a good choice for making washers is its ductility, which makes it soft and easily malleable. The ductility of copper makes it possible to form and shape it to meet the requirements of any application. Copper is an excellent conductor of heat and electricity and can be used for heat dissipation applications. It is a very cost effective material for the production of washers since its ductility reduces production time.
Brass Alloy
Brass is an alloy of copper and zinc and has many of each metal's positive properties. The low melting point of brass makes it very malleable and easy to shape. A typical use for brass is for applications such as plumbing and electrical work due to its low friction properties.
Chapter Six – Types of Metal Washers
There is an endless number of washers that are made for innumerable applications. Washers are an essential part of any product, component, or device that requires a secure connection between two surfaces. Though there is a long list of commonly used washers, there are even more washers that have been designed for special applications made of an assortment of metals and materials.
Under the three basic types of washers, which are spring, lock, and plain, are specialized washers designed to meet the specific needs of unique applications. As simple as the construction of washers may be, they have been an essential part of building and design for many years.
Metal Washers Types
Spring Washer
A spring washer has ends that are slightly raised to produce spring tension that has been created in the metal. They are placed above or below a nut or bolt. When the nut or bolt are tightened, the raised and lowered ends level to prevent nuts or bolts from loosening.
Types of Spring Washers
Conical – A conical washer has sides capable of supporting heavy force and can hold tension during thermal expansion and contraction. The deflection rate of a conical washer depends on its height and thickness.
Dome – A dome washer has the same structure as a conical washer, except its sides are rounded. They are capable of high load capacities with little deflection.
Wave – The unique structure of wave spring washers allows them to rotate in two directions to form a wave-like shape. They are ideal for use as cushion springs or spacers.
Finger – A finger washer has three curved flanges designed to reduce damping and noise, extra wear, vibrations, and skidding. They have similar load points as those of wave washers.
Crescent – Crescent washers look like flat washers that have been bent across the middle of the hole. The curve in the washer gives lighter pressure but still maintains its flexibility. They have uniform spring rates over the deflection range and are used for flexible and load cycling products.
Lock Washer
The name lock washer is a description of its purpose, which is to lock nuts and bolts in place. Lock washers are available in many forms, with split and teeth types being the most common. When the split or teeth are locked in place, the nut or bolt is prevented from loosening.
Types of Lock Washers
Split – A split lock washer is formed in the same way as a flat washer with a hole in the center and a metal ring. The variation in a split washer is a slit that has been made in the ring that causes the metal to take the form of a spring with one section above and the other below. The appearance of split washers as a spring has given them the name helical washers.
External Teeth – External teeth lock washers have evenly placed teeth around the circumference of the metal ring. When a bolt or nut is tightened, the teeth dig into the material’s surface being joined.
Internal Teeth – Like an external teeth lock washer, an internal teeth washer has teeth except that they are located on the interior of the diameter of the metal ring. Internal teeth lock washers are designed to absorb shocks and vibrations.
Plain Washers
Plain washers are the typical flat washer with a hole in the center and a metal ring. Though flat washers are very common and have been used for many years, they, as with other washers, have variations to conform to the needs of an application.
Torque – A torque washer has a square hole and pointy forks evenly spaced around the edge of its circumference. When a nut or bolt tightens a torque washer, the forks bite into the material’s surface to prevent the bolt or nut from spinning.
Flat – Plain flat washers are thin and round with a hole in the middle. They are designed to spread the load and support small head screws.
Fender – A fender washer has the same shape as a plain flat washer. They are different from flat washers in the size of their hole and the amount of metal in their circumference. The outside diameter of a fender washer is disproportionately larger in relation to its hole. The large amount of metal surface provides a large area to support the load.
Countersunk – A countersunk washer holds the fastener with a 90o to 120o counter at its top. They are designed for flat head screws with a counter. When tightened, the screw and washer form a flat surface.
Shoulder – A shoulder washer is a flat washer with a shoulder formed around the hole. They are a means of protecting wires, screws, and assemblies.
C-Washer – The C-washer has the shape of a plain flat washer with a large section of the metal diameter cut away to form the letter C. The slot of a C-washer is cut from the sides of the central hole out to the edge of the washer. Instead, they can be positioned or placed without the need to move or loosen the fastener.
Specialty Washers
Though the three common forms of washers listed above are the most widely used types of washers, specialty washers have the same function as traditionally shaped washers, with the exception that they do not have the circular oval form. They have an irregular shape on the outside or inside.
Square Washers
Square washers have a square exterior around what would be its circumference if it were circular. They can be flat or beveled on one or both sides. They are used with square headed bolts to prevent pull through and offer a larger surface area than traditional round washers.
Multiple Hole
A multiple hole washer is designed with continuous holes to avoid installing several washers that would have a small distance between them. They can more evenly spread the load over their connecting bar to create a uniform clamping force and exceptionally secure and tight connection.
Washer Standards
All washer manufacturers follow the standards for manufacturing as published by the International Organization for Standardization (ISO), which has created a set of quality standards in reference to all products that are produced for public and industrial use. Producers identify the adherence of their products to ISO standards 9001, 14001, and 18001, which relate to the quality of their products and prevention of harm to the environment.
Conclusion
A metal washer is a small flat piece of metal that has a hole in the center and is used as a spacer, a method for absorbing shock or distributing the load of a fastener.
There are few limitations on the types of materials that can be used to produce washers.
There are endless uses for metal washers, with specialty ones being manufactured for unique and unusual applications.
The wide assortment of washer configurations also includes a varied selection of metals.
All washer manufacturers follow the standards for manufacturing as published by the International Organization for Standardization (ISO), which has created a set of quality standards in reference to all products that are produced for public and industrial use.
Leading Manufacturers and Suppliers
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