This article takes an in depth look at metal washers and their use.
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A metal washer is a small, flat metal disc with a central hole, primarily used as a spacer, shock absorber, or load distributor for a fastener. The center hole in a metal washer is designed to accommodate the passage of a bolt or screw. Various manufacturing processes are employed to make metal washers, ensuring they possess adequate strength and resistance to stress.
The production of metal washers involves the use of diverse materials, with galvanized carbon steel and stainless steel being the predominant choices. The range of metals and shapes utilized results in a broad spectrum of washer types, including standard models like plain, spring, and lock washers. Beyond these common varieties, there's a host of specialty washers specifically crafted to accommodate unique application needs.
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 facilitate the loosening or removal of nuts from bolts and help secure them easily. They come in various types, suitable for both home use and industrial applications.
The primary function of washers is to distribute the load of a fastener evenly across the material it is connected to. Without washers, fasteners can cause surface stress, leading to cracks, impressions, and other deformities. Metal washers help mitigate this damage by evenly spreading the load and reducing stress on the surface. While stress relief is not always necessary, it is especially important for softer materials like wood.
Metal washers are also commonly used as spacers for fasteners that exceed the depth of the hole they are being driven into. For example, if a four-inch bolt is used with a material that is only three inches deep, a one-inch gap will remain between the bolt head and the material’s surface, leading to an insecure connection. By inserting metal washers between the surface and the bolt head, this gap is effectively filled, ensuring a secure fit.
Sealing washers are a specialized type of washer with a layer of material, such as neoprene, bonded to the metal. This combination of metal strength and sealing material creates a tight seal that prevents leaks and drips. While sealing washers are durable and resilient, their soft and smooth surface helps protect the sealed surface from damage. They are particularly effective for sealing bolt joints.
Proper installation of sealing washers is crucial, as over-tightening can cause leaks. The washer must be installed flush against the surface without being convex or concave.
The bonded sealing material not only provides a corrosion-resistant surface but also cushions the bolt head and seals the joint. In addition to preventing leaks, sealing washers also act as vibration dampeners.
A fender washer is a specialized type of washer designed for repairing connections where a hole has been damaged by rust or corrosion. It features a small central hole with a large outer diameter, allowing it to cover the damaged area while still accommodating a fastener.
Washers can be made from a variety of materials. While galvanized carbon steel and stainless steel are the most common, other metals like aluminum and copper are also used. The choice of metal depends largely on the intended application of the washer.
Hardened metal washers are specifically designed to maintain fastener tension in challenging conditions. Soft metals, such as aluminum and copper, are well-suited for applications where washers need to provide both sealing and load distribution.
Washers are manufactured through a stamping process carried out on a power press. The shape of the washer is formed by a die attached to the ram of the stamping or power press.
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 are custom-designed forms specifically made for manufacturing washers. Due to the small size of washers, multiple units are stamped or pressed from a single sheet of metal. The stamping process is efficient and smooth, capable of producing large quantities of washers while maximizing the use of metal sheets.
Various types of dies are used to produce a range of products, from simple to complex. These include simple, compound, progressive, transfer, combination, and multiple dies. For washer production, compound dies are typically used.
In the compound die process, multiple operations occur in a single stroke. For washers, this means that both the outer edge and central hole are formed simultaneously. The die punches and perforates the workpiece at a single workstation, with the washer's holes and shape being punched into the blank as it moves upward, while the scrap falls away.
The thickness of a washer is determined by the metal gauge, which affects the spacing it provides. The gauge system for measuring thickness dates back to the early Industrial Revolution, a time before universal thickness measurement standards were established.
Each type of metal has its own gauge chart due to the lack of uniformity across different materials. Generally, in these charts, a higher gauge number corresponds to a thinner metal.
The thickness of a washer also impacts its rigidity, support, and damping properties.
Below is the gauge chart specific to carbon steel.
| Carbon Steel Gauge Chart | |||||||
|---|---|---|---|---|---|---|---|
| Ga No. | Hot Rolled, HR P&O, Cold Rolled | Galvanized/Galvannealed | |||||
| Dec. Equiv. |
Toler.Range HR, 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 |
The selection of metal for a washer impacts its strength, corrosion resistance, brittleness, and cost. It's crucial to choose a washer that matches the material and application requirements to ensure optimal performance. While opting for a more durable or robust washer might seem beneficial, it could inadvertently cause damage to equipment or create safety hazards.
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.
Numerous machines are available in the United States and Canada for the production of metal washers. These machines play a crucial role in modern manufacturing by enabling efficient and precise mass production of washers, which are essential components in industries such as automotive, aerospace, construction, and appliances. Below, we explore several leading machines and their unique capabilities that contribute to their success.
Characteristics: The AIDA DSF Series Stamping Presses are renowned for their precision, speed, and reliability. They are capable of producing washers with consistent shapes and dimensions efficiently. The DSF series features advanced automation and servo control systems, facilitating rapid setup and changeover, which enhances overall production efficiency.
Characteristics: The Schuler MSP Series Mechanical Presses are distinguished by their sturdy construction and impressive power output. They are designed for high-volume washer production, offering rapid cycling times and precise repeatability. Their long-lasting durability and minimal maintenance needs make them a popular choice for efficient manufacturing.
Characteristics: Haas VF Series Vertical Machining Centers provide versatility and precision for crafting metal washers with intricate designs. They come equipped with advanced features, including high-speed spindles, rigid construction, and intuitive controls. These qualities facilitate efficient machining of diverse materials, making the Haas VF Series a preferred option for custom washer production.
Characteristics: These four-slide machines are engineered for the efficient production of small to medium-sized washers and intricate components. They utilize a distinctive four-slide forming process that minimizes material waste and performs multiple operations within a single cycle. Waterbury Farrel's machines are renowned for their precision, reliability, and user-friendly operation.
Characteristics: These screw machines, also known as cold formers or thread rolling machines, are highly effective for mass-producing metal washers. EBU Umformtechnik's machines are particularly adept at cold forming, a process that deforms material at room temperature to enhance strength and achieve a superior surface finish. These machines are favored for their cost-efficiency and rapid production speeds.
Please be aware that the availability, popularity, and technological advancements of machines can vary over time. For the latest and most accurate information, consult with manufacturers, industry experts, and current sources when evaluating the best options for metal washer production.
Washers come in a wide variety of configurations and metals. Essential characteristics of metals used for washers include resilience, strength, and durability. In certain applications, washers must also be flexible enough to form a seal and maintain a secure connection.
Selecting the right metal is a critical component of the washer production process, as using an inappropriate metal can lead to application or operational failures. The choice of metal is made based on the specific environmental conditions and usage requirements of the washers.
Stainless steel is an excellent choice for washer manufacturing due to its numerous beneficial properties. As a steel alloy containing chromium, stainless steel is highly resistant to rust and corrosion. The chromium reacts with oxygen and moisture to form a protective film that shields against corrosion and other damaging substances. Stainless steel washers are widely used across various industries, including petrochemical, aerospace, and automotive sectors.
Galvanized steel is protected against corrosion by a zinc coating. Initially, hardened steel is stamped to create the washer shape, which is then coated with zinc. Galvanized steel washers often have a rough, uneven surface and come in various colors. They are particularly well-suited for marine applications due to the zinc coating’s ability to safeguard against the corrosive effects of salt water.
Similar to stainless steel, aluminum offers a range of beneficial properties that make it an excellent choice for washer manufacturing. When exposed to air, aluminum develops a layer of aluminum oxide that provides effective corrosion resistance. Additionally, aluminum has outstanding thermal and electrical conductivity, surpassing many other metals. As a result, aluminum washers are commonly used in applications that require efficient heat dissipation.
Inconel is an alloy composed of nickel, chromium, and molybdenum, known for its exceptional strength and corrosion resistance at high temperatures. It can perform reliably across a broad temperature range, from cryogenic conditions up to 2200°F or 982°C. Inconel washers are designed to endure severe and harsh environments, with nickel and chromium offering resistance to oxidizing chemicals, while nickel and molybdenum provide protection in non-oxidizing conditions. Common grades of Inconel used for washers include 600, 601, 625, 686, 718, and 725.
Inconel’s robust resistance to corrosion, temperature stability, toughness, and strength make it an ideal choice for washers in demanding applications such as chemical processing, aerospace, marine industries, and oil and gas production.
Copper is an excellent choice for manufacturing washers primarily due to its high ductility, which allows it to be easily shaped and formed to meet specific application needs. Its ductility facilitates the production process, making it cost-effective and reducing production time. Additionally, copper is an outstanding conductor of heat and electricity, making it suitable for heat dissipation applications.
Brass, an alloy of copper and zinc, combines many beneficial properties of both metals. Its low melting point gives brass excellent malleability and ease of shaping. Brass is commonly used in applications such as plumbing and electrical work, owing to its low friction properties and durability.
Washers come in a vast array of types and are designed for countless applications. They play a crucial role in ensuring a secure connection between two surfaces in various products, components, and devices. While there are many commonly used washers, there are also numerous specialized designs made from a wide range of metals and materials for unique applications.
Among the three basic types of washers—spring, lock, and plain—there are specialized variants tailored to meet the specific needs of various applications. Despite their simple construction, washers have been a fundamental element in building and design for many years.
A spring washer features ends that are slightly raised to create spring tension within the metal. Positioned either above or below a nut or bolt, the spring washer's design ensures that as the nut or bolt is tightened, the raised and lowered ends compress to maintain a secure fit and prevent loosening.
Lock washers are named for their primary function: to secure nuts and bolts in place. Available in various designs, the most common types are split and toothed. These washers prevent loosening by locking into place when the split or teeth engage with the surface, ensuring a stable and secure connection.
Plain washers are the standard flat washers with a central hole and a simple metal ring. Although flat washers are widely used and have been a staple in various applications for many years, they come in different variations to meet specific application requirements.
While the three common types of washers mentioned above are the most widely used, specialty washers serve the same functions as traditional washers but with non-standard shapes. Unlike the typical circular or oval forms, specialty washers often feature irregular shapes on the outside or inside to address specific application needs.
Square washers have a square exterior, contrasting with the circular outline of standard washers. They can be flat or beveled on one or both sides. Designed to be used with square-headed bolts, square washers help prevent pull-through and provide a larger surface area compared to traditional round washers.
A multiple-hole washer features continuous holes, eliminating the need for multiple washers with small gaps between them. This design helps to distribute the load more evenly across the connecting bar, creating a uniform clamping force and ensuring an exceptionally secure and tight connection.
All washer manufacturers adhere to standards set by the International Organization for Standardization (ISO), which establishes quality benchmarks for products used in public and industrial applications. Manufacturers comply with ISO standards such as 9001, 14001, and 18001, which address product quality and environmental protection, ensuring their products meet rigorous criteria for performance and sustainability.
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