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How and when to use washers effectively

clock 2 minutes | 16 Mar 2018

Lots of black protective washers for fasteners

Threaded fasteners do a more reliable job when accompanied by washers. Most notably, washers protect the surface from damage during installation. They distribute the pressure and prevent the fastener from moving or corroding.

Skipping on washers can dramatically reduce the lifespan of how your product is put together. Ultimately, that leads to disaster for the product itself.

Not just any washer will do for all applications. Once you understand that, you can give washers the respect they deserve.

Common types of washers

For every type of washer, there are subcategories, but here are six different types you should know about.

Flat washers

Popular with: General manufacturing, maintenance and repair

Also known as plain washers, their purpose is to distribute the fastener’s load while reducing heat and friction during the tightening process. They can also be used as spacers, as is common in industrial and domestic applications. Flat washers are also called on to provide electrical insulation.

Lock washers

Popular with: Automotive, aerospace and domestic appliances

For fasteners that have a tendency to rotate or lose friction due to vibration or torque. There are many variations, but they all do this by holding the nut and bolt in place. Some bite into the bolt and the nut with their ends. Lock washers are a favourite in transportation industries such as automotive and aerospace. You’ll also find them in household appliances such as washing machines.

Tab washers

Popular with: Aerospace and Medical applications

Some consider tab washers as a type of lock washer while others think it stands on its own. Either way, it has a single tab or multiple tabs and notches that form to shape around bolts and nuts – or it’s designed to lie flat. Tab washes are ideal for harsh environments and stand up to extreme heat conditions or heavy vibrations.

Shoulder washers

Popular with: Electronics

Used as a bushing to insulate fasteners or shafts within electronic equipment. For this reason, shoulder washers are made of non-conductive materials, such as nylon. Avoid use in humid environments.

Countersunk washers

Popular with: Furniture, freshwater marine applications

Often described as looking like a miniature dog bowl without the bottom. These washers aren’t just functional, but also aesthetically pleasing. They allow flat or oval head countersunk screws to be installed flush with the part surface. You’ll often see them on consumer applications, such as cabinetry and furniture.

Spring washers

Popular with: Aerospace and automotive

These provide axial load to fasteners in case of vibration or thermal expansion, to limit movement. Spring washers are metallic and often preferred to similar springs that cost and weigh more, while taking up more space. They’re perfect for applications that require a degree of flexibility. All of these reasons are why the aerospace industry often uses spring washers in actuators on airplanes, including the flight controls and landing gear.

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