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Washers Technical Information Guide


Grainger Editorial Staff

A washer is a relatively thin disk or square with a pre-drilled hole that is placed beneath a nut, an axle bearing, or a joint as a seat to support and distribute the load. Additional uses are as a spacer, wear pad, pre-load indicating device, or locking device. Some types provide spring tension. Depending upon material, washers also insulate, seal, or provide an electrical connection.

 

WASHER TYPES

Structural

Top-bearing surface is cut at an oblique angle to compensate for nonparallel surfaces in structural leveling and shimming applications. Round or square.

 

Conical or Spring

Slight dish shape and edges sheared parallel to the center-line increase elasticity of joint for absorbing shock and maintaining tension under dynamic loads. Round.

 

Countersunk

Allows flat or oval head countersunk screws to be flush with surface for finished appearance. Round.

 

Fender

Large outside diameter provides extra-wide bearing surface for distributing force/stress; covers oversize holes. Round.

 

Flat

The most common type, with two flat surfaces for distributing force/stress of a nut or bolt and reducing friction and heat during installation of threaded fastener. Round or square.

 

Sealing

Made of relatively soft materials to form seal around a bolt or fastener; sometimes bonded to metallic washer. Round.

 

Slotted

A slot the same width as the hole diameter is cut from the center to the perimeter. Slips on and off shaft without removing fastener. Round.

 

Spherical

Two-piece equalizing assembly with one flat washer and one dish-shaped washer; eliminates unequal thread loads and stress from misaligned parts and nonparallel surfaces. Round.

 

Split Lock

Split with one end bent slightly outward to bite in and prevent loosening. Acts like a spring under compression to provide extra holding force and decrease frictional resistance during assembly and disassembly. Round.

 

Tooth Lock

Also referred to as Star washers. Directional teeth or serrated edges bite into fastener head/work piece to prevent loosening. Round.

 

Wave

Wavy shape provides compensating spring force, increases load-bearing capacity, absorbs shock and vibrations, and resists loosening and fatigue.

 

MATERIALS

Brass—alloy of copper and zinc that resists rust and moderate atmospheric corrosion. Not high in strength, but is durable and conducts electricity. Often used for appearance. Nonmagnetic.

Nylon—used extensively in electronics applications. Nonconductive, durable, and ductile material resists heat, corrosion, and nonacidic chemicals. Has excellent insulating properties, but dimensions can be affected by moisture absorption. Lubricated nylon is trade named Nylatron™.

Stainless Steel—contains a minimum of 12% chromium for exceptional resistance to extreme environmental conditions. Contains highly anticorrosive properties. Not affected by scratching; however, not as strong as common alloy steels. May be mildly magnetic.

18-8 Stainless Steel—contains approximately 18% chromium and 8% nickel. Provides excellent protection against rust and corrosion. The material of choice for prolonged outdoor use or exposure to salt spray and chemical fumes. May be mildly magnetic. Comparable to ASTM 300 Series and ISO A2.

316 Stainless Steel—contains a minimum of 2% molybdenum for superior corrosion resistance and reduced risk of pitting in extreme environments. Is nonmagnetic and can't be heat treated or hardened. Comparable to ISO A4.

Steel—the most common fastener material. Available in these types:

  • Alloy Steel contains enough alloying elements (other than carbon) to affect the fastener's properties; generally more responsive to heat and mechanical treatments.
  • Plain Steel (or Carbon Steel) contains only carbon and residual amounts of any other impurities. It is magnetic and malleable and can be either cast or wrought.
  • Spring Steelis a high-carbon or alloy steel used in the manufacture of springs or where high tensile properties are required.

Synthetic rubber—used for applications requiring resistance to water. Types include EPDM (ethylene-propylene rubber) and Neoprene™ (ploychloroprene-based rubber).

Thermoplastics—comprised of various compounds characterized by low weight, high strength, electrical insulating properties, and resistance to corrosion and chemicals. Include acetal, Kapton™, phenolic, polycarbonate, UHMW polyethylene, polypropylene, and PVC (polyvinyl chloride).

 

The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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