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.
Washers are made from a variety of materials, the most popular of which are galvanized carbon steel and stainless steel. Carbon steel is stronger than stainless steel, but stainless steel will not rust or corrode like carbon steel can.
Other metal washers include zinc, copper, brass, and iron. You can also find specialty washers, such as plastic washers, rubber washers, ceramic washers, and phenolic washers.
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.
Type of Washers
There are many different types of washers for a variety of applications.
- Structural Washer
- Belleville washer
- Countersunk Washer
- Fender Washer
- Flat Washer
- Sealing Washer
- Slotted Washer
- Spherical Washer
- Split Lock washer
- Tooth Lock washer
- Wave washer
- Torque Washer
1. Structural Washer
Structural washers are thick, strong washers used in heavy-duty building construction. For outside building applications, structural washers are typically coated or galvanized for corrosion resistance.
- Top-bearing surface is cut at an oblique angle to compensate for nonparallel surfaces
- Shape: Round or square
- Use: Structural leveling and shimming applications
2. Conical or Spring Washer / Belleville washer
A Belleville washer, also known as a coned-disc spring, conical spring washer, disc spring, Belleville spring, or cupped spring washer, is a conical shell that can be loaded along its axis either statically or dynamically.
A Belleville washer is a type of spring shaped like a washer. It is the frusto-conical shape that gives the washer its characteristic spring.
The “Belleville” name comes from the inventor Julien Belleville who in Dunkerque, France, in 1867 patented a spring design that already contained the principle of the disc spring. The real inventor of Belleville washers is unknown.
Through the years, many profiles for disc springs have been developed. Today the most used are the profiles with or without contact flats, while some other profiles, like disc springs with trapezoidal cross-section, have lost importance.
Slight dish shape and edges that are sheared parallel to the centerline to increase the elasticity of join.
Shape: Round
Application: Used for projects that involve thermal expansion. Good for absorbing shock and maintaining tension under dynamic loads
3. Countersunk Washer
Countersunk washers serve the same function as a flat washer, but they provide a bearing surface for flat head screws. An additional application is providing a sealing function for flat head screws.
Countersunk washers sometimes referred to as finishing washers, have a countersink that captures the head of the fastener. When secured they provide a flush surface and are available in several shapes including 90 degrees countersunk, angle countersunk, flanged, un-flanged, and rolled flange among others.
- Allows flat or oval head countersunk screws to be flush.
- Shape: Round
- Use: Allows for a finished appearance
4. Fender Washer
A fender washer is a flat washer with a larger outer diameter in proportion to its center hole. They are made from a thinner gauge metal than most flat washers and are designed to spread the load on thin sheet metal. Often used in sheet metal, plumbing, and electrical work.
The name is derived from their use in the automotive industry where they are used to mount fenders. They distributed a load evenly across a large surface area. Flat washers whose outer diameters measure more than three times the inner diameter are commonly referred to as fender washers.
- Large outside diameter provides extra wide bearing surface
- Shape: Round
- Used to distribute force/stress and can cover oversized holes
5. Flat Washer
Flat washers protect surfaces by evenly distributing torque when a bolt or screw is tightened. They prevent corrosion between a steel screw and an aluminum surface. A nylon washer can be placed under a machine screw to reduce noise and abrasion and offer electrical insulation. Sealing washers are used for plumbing and hydraulic projects.
Flat washers, also referred to as Type A plain washers, are thin, flat, and circular general-purpose washers with a centrally located hole. Standardized flat washers may be designed by the use of imperial or metric dimensions.
Standard imperial washers include SAE washers, for use with fine threaded nuts and bolts, and USS flat washers, for use with coarse threaded bolts and nuts. Standard metric washers are available in several gages as defined by JIS standards.
- The most common type of washer, with two flat surfaces
- Round or square Shape
- Used to distribute force/stress of a nut or bolt and reduces friction and heat during installation of threaded fastener
6. Sealing Washer
Sealing Washer (Plural Sealing Washers) A Rubber or Neoprene Washer, Sometimes Metal-Backed, Typically Placed on A Fastener to Prevent Water from Migrating into And Through the Fastener Hole.
When installed in a sealing application, the materials in Sealing Washers compress against either a flexible or an inflexible surface to permanently seal in or seal out any operating environment, whether natural or industrial. Tight against the surface, Seal flows inward to seal minor fastener diameter and surface voids.
Sealing washers are circular seals with a rectangular cross-section. They are normally made of annealed copper, annealed aluminum, and fiber. They are used to ensure seals on hydraulic couplings where pressure is not high.
7. Slotted Washer
C-washers have a slot cut from the center to the perimeter. Typically, the slot is the same width as the “center hole,” allowing the washer to be removed, replaced, or inserted without completely removing the fastener.
Slotted “C” flat washers allow you to assemble and disassemble bolted joints without taking bolts, nuts, and washer installation apart. The open slot allows the C-shaped washer to be slipped in and out. Washers are extra-thick for extra strength.
8. Spherical Washer
Spherical washers are designed to create an exact, parallel plane between the bolt head and the face of the nut. These washers automatically adjust and compensate for the angular deviation between the planes and prevent the bolt from bending.
- Automatically compensates for angular errors
- Evenly distributed bolt tension
- Reduces bolt fatigue from bending bolts
- Improved bolt stretches possible due to increased clamping length
- Surface treated for protection in humid and harsh environments
9. Split Lock washer
Split ring washers use friction to prevent bolted joints from loosening. They feature a ring that has been split and twisted – creating two sharp edges. These washers are installed between the bolt head/nut and mating surface, the bolted joint is then tightened in the same way as an unsecured bolt.
Split washers have been experimentally proven to be ineffective locking devices and can even aid self-loosening over time.
Use a split lock on a small, low-intensity job, since bigger loads will flatten the washer and make it useless. Use tooth lock washers for extra force. With their jagged edges, tooth lock washers hold the nut or threaded fastener in place with a significant amount of force.
10. Tooth Lock washer
Tooth lock washers (electrical contact washers) are designed to prevent bolted joints from loosening using friction. Similarly, to serrated washers, tooth lock washers feature teeth-like serrations either internally or externally. When the bolted joint is tightened, these teeth bite into the mating surface.
- External tooth lock washers have a cylindrical inner diameter with several teeth along the outside diameter that are aligned at an obscure angle to the face of the washer. They are designed for use with wide headed fasteners. When secured, the teeth bite into a mating surface while they resist the compressional force.
- Internal tooth lock washers have a cylindrical outer diameter with several teeth along the inside diameter that are aligned at an obscure angle to the face of the washer. They are designed for use with shallow headed fasteners. When secured, the teeth bite into a mating surface while they resist the compressional force.
11. Wave washer
Wave washers, also commonly referred to as wave springs or coiled wave springs, are used to absorb stress due to axial compressive loads, acting as a cushion. The waves of the wave washer provide 3, 4, or 6-point contact that results in greater load-bearing capacity and a medium range of deflection.
The height and material thickness regulate the load function. Wave spring washers are typically used in thrust loading applications for small deflections, particularly where radial space is limited. Wave washers can help offset tolerance deviations in the assembly process and reduce loosening due to vibration.
- Available in carbon and stainless steel
- Offered in clear zinc, yellow zinc, and black oxide finishes
- Requires less operating space than traditional coil springs
- Evenly distributes applied loads
- Minimal sharp edge interference or gall
12. Torque Washer
A torque washer is a type of washer designed for use in a soft, penetrable material in which a bolt would probably not be able to stay fastened tightly inside.
For instance, bolts can come loose in softwoods over time, especially if the surrounding environment is prone to cause significant warping, variable in temperature, or if the wood or bolt itself carries a variable load.
Torque washers are designed to combat bolts loosening over time in the following ways:
- Four prongs that dig into the material, anchoring the bolt in place
- Prongs increase the surface area contact between the mating surface, washer, and bolt
- They are stamped from a single metal sheet to prevent breakage
- Square holes that fit a carriage bolt’s square shank
