Washers Selection Guide
Spring Washers
Spring washers, also known as disc springs, leverage the unique properties of their material profile: irregularities within the washer compress with proportional resistance, reverting to their original shape after deflection. These washers find application in assemblies requiring play take-up, maintenance of assembly tension, compensation for material expansion or contraction, absorption of intermittent shock loads, and controlled reaction under dynamic loads.
Belleville Washers
Belleville washers excel in supporting high loads with minimal deflection, with load and deflection capabilities dictated by the height-to-thickness ratio. They are commonly utilized in thermal expansion applications.
Crescent Washers
Designed for lighter loads, crescent washers provide uniform spring rates throughout deflection, making them suitable for flexible, load-cycling applications.
Dome Washers
Dome washers boast a high load capacity with minimal deflection. Unlike crescent washers, dome washers feature ground curves to create a flatter load-bearing surface.
Finger Washers
Characterized by their split construction and protruding flanges, finger washers combine the flexibility of crescent washers with distributed load points, making them ideal for noise and vibration dampening.
Wave Washers
Wave washers offer moderate load capacity and deflection, serving primarily as cushions or spacers. They feature multiple waves within the washer for enhanced flexibility.
Single Wave Washers
Similar to crescent washers, single wave washers feature flattened load points to minimize abrasion against sensitive surfaces.
Spring Washers: Characteristics and Applications
Spring washers possess a spring rate, defining their deflection range and load capacity. These ratings can be adjusted by stacking spring washers in series or parallel configurations to suit specific application requirements. For further details, refer to the Spring Washer Selection Guide.
Washers Selection Guide
Lock Washers
Lock washers are specifically engineered to secure fasteners prone to rotation or loss of friction. While there are various types of lock washers, each tailored for specific fasteners or applications, they operate on the same fundamental principle. These washers exert a load, partially deform, and lock a fastener in place. Typically, a split coil or teeth of the lock washer bite into the fastener’s head and against another flat surface. In certain applications, they are used in conjunction with flat washers to evenly distribute the load without deforming the assembly.
Helical Lock Washers
Also known as split lock washers, helical lock washers feature a single coil of non-continuous flat wire filament. Each end of the coil is bent outward toward a mating surface. Upon securing, the lock washer flattens as each end of the coil bites into the mating surfaces.
External Tooth Lock Washers
Designed for wide-headed fasteners, external tooth lock washers have a cylindrical inner diameter with several teeth along the outside diameter. These teeth, aligned at an obscure angle, bite into a mating surface while resisting compressional force.
Internal Tooth Lock Washers
Internal tooth lock washers, on the other hand, are tailored for shallow-headed fasteners. With a cylindrical outer diameter featuring teeth along the inside diameter, they bite into a mating surface while resisting compressional force.
Other Common Types
- Flat Washers: General-purpose washers with a centrally located hole, available in imperial or metric dimensions.
- C-Washers: Feature a slot from the center to the perimeter, facilitating easy removal or insertion without fully removing the fastener.
- D-Shape Washers: Feature a flat edge cut away on the perimeter, preventing the washer from turning when mounted.
- Countersunk Washers: Capture the head of the fastener with a countersink, providing a flush surface.
- Fender Washers: Have a large outside diameter compared to the inside diameter, distributing load evenly across a large surface area.
- SAE Washers: Approved by the Society of Automotive Engineers, designed for use with fine thread bolts and nuts.
- Torque Washers: Prevent rotation of the washer with sharp prongs sinking into the mating surface.
- Shoulder Washers: Feature an integral cylindrical sleeve to segregate the fastener from the material it is secured to.
Mechanical Guidelines for Fasteners – Screws, Nuts, Bolts, Washers, Pins
| Steel Grade | Material & Treatment | Proof Load Stress (ksi) Min. | Yield Strength (ksi) Min. | Tensile Strength (ksi) Min. | Core Hardness, Rockwell | Standards Authority |
|---|---|---|---|---|---|---|
| Low-carbon grade 2 | Low/medium carbon steel, cold-forged | 55 | 57 | 74 | B70-B100 | Society of Automotive Engineers |
| Grade A | Low/medium carbon steel | 90-100 | 95-105 | 60 | B69-B100 | American Society for Testing & Materials |
| Grade B | Low/medium carbon steel | 70-133 | 76-139 | 60-100 | B69-B95 | American Society for Testing & Materials |
| Grade 5 | Medium carbon steel, quenched & tempered | 74-85 | 81-82 | 105-120 | C19-C34 | Society of Automotive Engineers |
| Grade 8 | Medium carbon alloy steel, quenched & tempered | 120 | 130 | 150 | C33-C39 | Society of Automotive Engineers |
| Grade C | Medium carbon steel | 144 | 154 | N/A | B78-C38 | American Society for Testing & Materials |
| 2-H | Medium carbon steel | 144 | 154 | N/A | B78-C38 | Society of Automotive Engineers |
Strength guidelines may vary by part thickness, number of threads/inch, finish, and other design or production factors.
Table Credit: Instock Fasteners
Materials of Construction
The selection of materials for washers depends on their intended application and the specific requirements of the fastening system. In applications involving cyclic loading, such as those utilizing spring washers, materials with high yield strength and fatigue resistance are imperative. This often necessitates the use of high-alloyed steels or spring steel. Conversely, softer materials are preferred for washers subjected to lighter loads or when mating with soft surfaces susceptible to damage by metallic washers.
Metallic Materials
Various metallic materials are available for washer construction, including aluminum, brass, copper base alloys or bronze, copper, nickel base alloys, spring steel, steel, hardened steel, stainless steel, and titanium.
Non-Metallic Materials
Non-metallic materials offer alternative options for washer construction, encompassing ABS, acetal, asbestos, felt, leather, nylon, polyester, polycarbonate, polyethylene, PVC, polypropylene, PTFE, and rubber.
Corrosion Resistance
Non-Steel Washer Springs
Washer springs made from non-steel materials are typically crafted to resist corrosion effectively. Conversely, for steel washers, a condensed array of corrosion prevention techniques is outlined below.
Phosphating
Involves the application of a zinc-phosphate layer coupled with a corrosion-protective oil. While suitable for most applications, phosphating can exhibit abrasive properties.
Browning
Produces an oxidized surface treated with oil. This method, though not as effective as phosphating, is utilized when a smoother finish is required.
Metallic Coatings
Common coatings such as zinc, cadmium, and nickel are frequently employed. Zinc acts as a sacrificial anode, corroding before the washer material. Cadmium offers superior protection but poses environmental and biological risks. Nickel, while resistant to many corrosive agents, can act as a cathode, potentially leading to attacks on the base metal. Hence, a dense, non-porous nickel coating is imperative.
Electroplating
Utilizes various metals as surface coatings, yet is susceptible to hydrogen embrittlement, which may reduce fatigue life.
Peen Plating
Involves using a peening body along with metallic powder in the shot peen process, embedding it into the washer.
Metal Spray
Primarily employed for large spring washers, where conventional plating methods pose challenges, resulting in a thick coating. However, adhesion to the washer may be inferior compared to other metallic coatings.
Chemical Plating
Utilizes a nickel-phosphor alloy precipitated onto the surface via a chemical process, boasting exceptional corrosion and abrasion resistance.
Dacromet Coating
Incorporates zinc and aluminum flakes within a chromatic compound, baked onto the washer, offering robust corrosion protection.
FAQs
Q: What are the dimensions of 1-inch washers?
A: 1-inch washers typically have an outer diameter of 1 inch.
Q: What are the specifications of 3/4-inch washers?
A: 3/4-inch washers typically have an outer diameter of 3/4 inch.
Q: What are the dimensions of 3-inch washers?
A: 3-inch washers typically have an outer diameter of 3 inches.
Q: What are the specifications of 4-inch washers?
A: 4-inch washers typically have an outer diameter of 4 inches.
Q: What are the dimensions of 5/16-inch washers?
A: 5/16-inch washers typically have an outer diameter of 5/16 inch.
Q: What are AN washers?
A: AN washers are aircraft-grade washers conforming to specific standards set by the Aerospace National (AN) standards.
Q: What are the uses of bolt and washer combinations?
A: Bolts and washers are commonly used together to distribute the load and provide a secure fastening in various applications.
Q: What are the types of bolts and washers available?
A: There are various types of bolts and washers, including flat washers, lock washers, and spring washers, each serving different purposes in fastening applications.
Q: Is there a chart detailing the types of screws available?
A: Yes, a chart detailing the types of screws, including their sizes and specifications, is available for reference.
Q: What are the sizes of fender washers?
A: Fender washers come in various sizes, typically ranging from small to large to accommodate different applications.
Q: What are the differences between fender washers and flat washers?
A: Fender washers have a larger outer diameter compared to flat washers, providing a wider surface area for load distribution.
Q: What are the dimensions of flat washers?
A: Flat washers come in various dimensions depending on their size and application requirements.
Q: Is there a chart available for flat washer dimensions?
A: Yes, a chart detailing flat washer dimensions is available for reference, providing information on outer diameter, inner diameter, and thickness.
Q: What is the recommended order for using flat washers, lock washers, and nuts?
A: The recommended order is to place the flat washer first, followed by the lock washer, and then the nut for optimal fastening performance.
Q: What are the standard sizes available in flat washer size charts?
A: Flat washer size charts typically include standard sizes ranging from small to large to accommodate various bolt and nut sizes.
Q: What is a grooved washer used for?
A: Grooved washers are designed to provide additional grip and security in fastening applications, especially in high-vibration environments.
Q: Are there specific sizes available for large metal washers?
A: Yes, large metal washers come in various sizes to accommodate different bolt and nut sizes in heavy-duty applications.
Q: What are the common uses of large washers?
A: Large washers are commonly used in construction, automotive, and industrial applications to provide stability and support in heavy-duty fastening tasks.
Q: What are the different types of lock washers?
A: Lock washers come in various types, including split lock washers, external tooth lock washers, and internal tooth lock washers, each designed to prevent screws and nuts from rotating and loosening under vibration or torque.
Q: What are metal washers?
A: Metal washers are flat discs made of metal, such as stainless steel or copper, used in conjunction with screws and bolts to distribute the load, prevent surface damage, and provide a stable connection.
Q: What is a screw with washer attached?
A: A screw with a washer attached typically refers to a screw that comes with a built-in washer or has a washer secured to its head. This design helps distribute the load and provides additional support during fastening.
Q: How are screws and washers used together?
A: Screws and washers are commonly used together in fastening applications to provide a secure and stable connection. The washer is placed under the screw head or nut to distribute the load and prevent damage to the surface.
Q: What are square washers?
A: Square washers are flat washers with a square-shaped hole in the center. They are used to prevent rotation and provide a larger bearing surface when used with square-headed bolts or nuts.
Q: What are the standard washer dimensions?
A: Standard washer dimensions vary depending on the type and size of the washer. However, they typically range from small diameters of a few millimeters to larger diameters of several inches.
Q: What are steel washers?
A: Steel washers are flat discs made of steel, often stainless steel or carbon steel, used in mechanical and construction applications to distribute the load of a threaded fastener and prevent surface damage.
Q: What is a threaded washer?
A: A threaded washer is a washer with internal threads, allowing it to be screwed onto a bolt or threaded rod. This type of washer provides additional stability and security in fastening applications.
Q: Where can I find a washer dimensions chart?
A: A washer dimensions chart provides information on the standard sizes and dimensions of washers, typically categorized by diameter, thickness, and material.
Q: What is a washer nut bolt diagram?
A: A washer nut bolt diagram illustrates the arrangement of a washer, nut, and bolt in a fastening application, demonstrating how they work together to provide a secure connection and distribute the load.
