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A plate washer is a type of hardware used with a variety of bolts and other fasteners. It consists of a round or square metal plate with a hole in the center to fit around the fastener. Plate washers tend to feature a thicker and heavier construction than a standard washer, making them appropriate for heavy-duty applications. Using a plate washer improves the security of the connection, and adds strength and support. Manufacturers produce a wide variety of plate washer sizes and designs to meet the needs of different types of installations.
When installing a plate washer, builders start by drilling a hole in the material being fastened. They then slide the plate washer on top of the material until the hole in the washer lines up with the freshly-drilled hole in the material. The installer then inserts the bolt through the holes and tightens it using a wrench or similar tool. The plate washer prevents the head of the bolt from crushing the material underneath, both during installation and after.
A plate washer also improves the hold between the bolt and the material, increasing the strength and durability of the connection point. This helps to prevent wood from splitting in a sill plate application, for example, and maximizes the chance that the connection will last. It also spreads the load over a wider area, reducing the direct force on the fastener and surrounding area.
Plate washers come in many sizes and thickness, as well as different shapes and profiles. Thicker or larger plates may be required at large-scale applications, while smaller units may be appropriate for more basic projects or lighter loads. Steel plates can be used at many indoor applications, while galvanized or stainless models may be needed in moisture-prone areas to help prevent rust or corrosion. The plates may be painted to match bolts or surrounding surfaces, or left unfinished.
When used on wood structures, the plate washer is often left exposed. Installers may choose round or square units to create the desired appearance and to complement the design of the fasteners. Some plate washers even feature an ogee or beveled appearance to enhance the aesthetic appeal of the installation. Others feature a decorative design, or specialty finish, including copper, brass, and chrome. To enhance design appeal, a plate washer may be used simply for visual appeal, even when it's not needed to improve strength or stability.
@umbra21 - Your comment makes me think of this saying I read in a book sometime. A kid was asking a blacksmith why he bothered to spend so much time on the part of a wagon that was not going to be seen by anyone, once the wagon was built.
The smith replied, that HE would know the part was there, so he wanted to do a good job for his own piece of mind.
Using a washer is one of those things that doesn't seem to have much point, until a few years later when you realize spending a couple of cents and seconds more would have saved a lot of work.
I guess what it comes down to is that wood is quite a soft material and will change over time. You might think you can skip using a washer, but in the long run it is a good idea to do everything you can to make your connections strong and durable.
Washers are often included in the same packaging with bolts, so you really haven't got much of an excuse not to use them.
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