why do we use washers with bolts

Why Do We Use Washers With Bolts?

When I was watching an instructional video about installing bolts onto a surface, I became curious about the washers that were installed with it. What is their purpose and why are they used in this situation. So, I did all of the research to find out the answer to this question.

Why do we use washers with bolts? Washers are used with bolts in order to avoid any damage that can occur under the head of the bolt onto the surface. Without the use of a washer, the bolt could potentially cause scratches and experience torque problems.

During the process of securing a bolt into a surface, using a washer just seems like second nature at this point. Most people never question why the washer is needed. If you are interested in this topic just like I was, keep reading to find out everything you need to know.

Why Washers Are Used With Bolts

Whenever a bolt is secured between any two surfaces, it has always been a general rule to use a washer along with it. Why are these little round objects necessary when it comes to installing a bolt?

Before we can get in depth about why washers are necessary to use with bolts, we will need to establish a clear understanding of each of these components.


  • Flat disc
  • Made of metal
  • Installed under bolt head


  • Small metal fastener
  • Joins two surfaces
  • Looks similar to a screw

A washer is a flat, round disc, that is usually made of metal or a similar material. However, washers can sometimes be made of plastic or rubber in some instances. These tiny pieces are installed under the head part of a bolt.

A bolt is a small metal fastener that joins two separate surfaces together on each end. While it looks similar to a screw, it is much thicker and more durable.

So, why are washers needed when you are fastening something together with a bolt? There are more reasons than one why these handy little pieces are beneficial. Take a look at the list below for a brief synopsis on why this is, or keep reading for further details.

Why Washers Are Used With Bolts:

  • Protects the surface from scratches
  • Prevents the bolt from sinking
  • Evenly distributes pressure and force
  • Provides a smooth surface for the bolt
  • Fills up empty space when necessary
  • Helps longer bolts to be tightened

The first reason why washers are used with bolts is to protect the surface from scratches. Without the presence of a washer, the rough and sturdy head of the bolt can potentially cause damage by scraping against it unprotected.

Additionally, the washer will hold the bolt head up, preventing it from sinking down into the surface. Evenly distributing pressure and force, the bolt will not run the risk of negatively affecting the surface it is installed into by digging into it or becoming lop-sided.

The washer will also provide a smooth surface for the bolt to rest on. Instead of securing it into the surface directly all by itself, the bolt will also be protected from damage with the even texture of the metal washer directly underneath it.

If you ever find yourself in a circumstance where the place in which the bolt needs to be installed has too large of a circumference for the bolt to be able to fit into, a washer can become the solution to this problem.

Without the use of the washer, the entire bolt might fall through the hole completely since it is not big enough to stay up on its own. When a washer is installed with it, on the other hand, it will be able to fill up the empty space that the bolt itself cannot provide.

Lastly, washers can help longer bolts to be fastened securely into the desired surface. In the event that the length of the bolt is too long, you will be able to tighten it effectively with the use of a trusty washer.

Which Side of a Washer Goes Down?

When it comes time to attach a washer to a bolt during installation, you might be wondering which side of the washer should be facing down. First of all, how are the sides of a washer classified, and how can they be identified?

The two sides of a washer are classified as the rounded side and the burred side. The rounded side, quite obviously, is the side of the washer that has visibly rounded corners. When classifying your washer, if you are not able to point out the round side with just your eyes, you can use your thumb to feel the texture of the corners.

The burred side has a sharper edge to it, which can also be pointed out by looking at it or by running your finger along the corners to differentiate the two.

There is no official rule for which side of the washer should go up or down in any circumstance, but there is a preference when it comes to bearing surface pressure.

Washers are installed with bolts to make sure that they are not exerting too much pressure on the surface that it is secured into.

If a bolt is secured without the presence of a washer, the head will eventually start to wedge itself deeply into the surface, which could cause it to sink at some point. However, this can still happen even when the washer accompanies the bolt, if it is installed on a certain side.

Burred Side Down:

  • Keeps the bolt from sinking
  • Prevents digging into the surface

Rounded Side Down:

  • Prevents the plating from peeling
  • Gentle surface barrier between bolt and surface

In order to avoid digging and sinking of the bolt all together, you will want to place the washer with the burred side facing down.

That way, the burrs on the edges of this side of the washer will be able to mark the surface firmly underneath the bolt that is being fastened.

Alternatively, if this is not as much of a concern for you as plating peeling of the surface is, you will want to install the washer with the rounded side down. This will create a gentler surface for the rightly secured bolt.

Regardless of what your preference is while installing your bolt when it comes to washer direction, it is always important to use a washer in any circumstance to protect the surface of whatever you are securing it into.

How to Use Washers with Bolts

When you are ready to secure your bolts into place with the use of a washer, you can refer to these quick steps in order to get this done correctly.

How to Use Washers and Bolts Together:

  1. Insert the bolt into the washer
  2. Make sure the correct side is down
  3. Turn the bolt head using a fitting wrench
  4. Tighten the bolt until the head touches the washer
  5. Secure the bolt into the surface with a torque wrench
  6. Continue to turn the torque wrench until it pops

To use washers and bolts together, you will need to begin by inserting the bolt into the washer. This can be done by placing the long side through the hole first, leaving the head on the other end.

Depending on which side you would like to be facing down, which was explained previously, you will want to make sure that it is properly rotated before proceeding to the next steps.

Next, you will find any kind of wrench that will fit the size of the bolt’s head in order to fasten it further into the washer. During this step, you will need to tighten it until the head of the bolt is touching the surface of the washer.

After that, you will be ready to secure the bolt and washer together into the surface of your choice. This can be done using a torque wrench for the easiest and most convenient process.

Secure the bolt into the surface using your torque wrench, and continue to turn it clockwise until it pops, indicating that the correct torque has been reached.

Once you receive notification of this, you will know that the bolt and washer have been successfully installed into the surface.

Related Questions

What is the purpose of a lock washer?

A lock washer, in comparison to a regular metal one, is a special object that keeps nuts and bolts from slipping out of place. This is usually due to vibrations that occur on the surface or high levels of torque. While each lock washer is different, their main purpose is to hold the nuts and bolts in the same place securely.

What is the difference between a nut and a bolt?

Both bolts and nuts are usually used together to secure two separate surfaces together tightly. The bolt however is more like a screw, while the nut is a small metal object that takes the shape of a hexagon.