Washers and bolts may look terribly simple. They really only have one job: tightening and securing just about anything, from alternators to wood beams. Even so, it's deceptively easy to misuse them if you're not careful. To avoid problems and ensure the most secure connection possible, it's smart to learn exactly how to use washers and bolts to get the result you need.
What Are Washers and Bolts?
A washer is simply a small flat disc, usually made of metal (but sometimes made of rubber or plastic) that is inserted underneath the head of a bolt. When the bolt is tightened, the washer's function is to disburse pressure evenly between two adjoined items or surfaces. It operates as a spacer or a seal.
The bolt is a small fastener that connects or joins up the two surfaces. Usually made of metal, the bolt is sometimes referred to mistakenly as a "screw."
However, there are differences between the two. A bolt generally has threads and a flattened head. If the fastener mates with prefabricated internal threading, or creates its own threading, then it's called a screw.
Selecting the Right Bolts
Most bolts at the hardware store are made of stainless steel or galvanized steel. Use bolts made of galvanized steel for outdoor projects. Stainless steel bolts are used for indoor projects.
Choose the proper bolt material for your job. Bolt materials and standards are listed on the bolt head. The numbers below the manufacturer designation notate the ASTM codes the bolt conforms to.
Sizing the Washers and Bolts Correctly
Size the bolt to the mounting hole. Check the proper size of the mounting hole through the manufacturer's documentation, then find the right bolt sized to that hole. If the hole does not specify a diameter, try different sized bolts until one fits perfectly in the hole.
You'll also want to size the washer to the bolt accurately. The washer fits around the shaft of the bolt, and slides all the way up to the bolt head. No friction should exist between the washer and bolt.
Working With Washers and Bolts
To use your washer and bolt properly, first insert the bolt into the washer. Next, slide the bolt and washer into the mounting hole. Once the bolt is threaded into the hole, begin turning the head of the bolt using the appropriate sized wrench. Tighten the bolt down to the washer until the head contacts the washer.
Tighten the bolt with a torque wrench, if this is called for in your installation instructions. Place the torque wrench over the head of the bolt, and turn it until the torque wrench pops and gives you a reading. When the reading matches the proper torque required for your assembly, the bolt and washer are properly tightened.