The other day, I was working on a project in which the screws I was using were buried a bit too deeply and I needed to pull them out a bit. Since I imagine that many of you have wondered whether or not washers are necessary when using wood screws, I though I’d provide the answer here.
In most cases, washers are unnecessary when using wood screws. To keep wood from warping, a screw head is usually all that’s needed. It is rare to get a lag bolt with a countersunk head, thus it is only with these that washers are used.
I’ll explain why washers aren’t required for most wood screws and provide more context for when they can be useful.
What Is The Purpose Of Washers?
The purpose of a washer is to disperse the force applied by a threaded insert, like a bolt or screw, across the surface it is fastened to. They are available in a wide range of diameters to accommodate any type of bolt or screw.
The usage of washers for this purpose is a case in point. My favourite usage for washers is right here. When I need a hinged joint between two wooden parts that will be fastened together with a bolt, I use a washer.
As I will explain below, washers can be used for a variety of additional purposes as well.
Reasons You Might Want To Use A Washer
Some woodworking tasks call for the use of washers for various reasons.
Distributing the force of the screw, a washer can be used to keep a glued joint tightly compressed while the glue dries.
A washer, or multiple washers, can be used to create space between two parts of an assembly.
When working with a particularly soft wood, the wood screw may sink too deeply into the surface, preventing the board from being held together. A washer can assist stop it from happening.
After the screw is driven into some types of wood, the wood may split along the screw’s path. This is because the screw’s head causes the wood fibres to separate. One’s load will be spread out more uniformly while using a washer.
Most wood screws are made to sink into the surface, rather than leave any visible marks on it. Some screws, like coach screws, are designed to be visible on the exterior of the wood’s surface and feature a hexagonal head to facilitate this. These fasteners can’t be properly tightened without a washer, which prevents them from biting into the surface.
Reasons Not To Use Washers
Woodworking projects of the sort we cover here are often more refined pieces intended for indoor display. Several factors suggest that a washer is not the best choice for your next woodworking project.
Washers behind your screws will seem unpleasant on a beautiful finished product, so avoid using them if you care about aesthetics.
Make a mark on the surface; in most woods, a washer pressed firmly against the surface by a screw will create a ring imprint.
Not a good idea; most wood screws are created to be driven directly into the wood and do not require washers.
These pros and cons should help you make an informed decision about whether or not to include a washer in your next woodworking project. You must decide for yourself if the positives outweigh the negatives.
Types Of Screws
In light of the foregoing, there are really just two reasons to use a washer.
The kind of fastener being used
Required joint type
First, I’ll talk about the potential screw or mending you’ll need. Insights like these can guide your selection of a washer.
The majority of woodworking screws feature a threaded shaft and a countersunk head with ribs under the head to help it sink into the timber surface.
These screws are typically used without a washer because they are made to completely disappear into the wood once installed. A washer wouldn’t work with these screws since the screw head would rest on top of the washer.
As a rule of thumb, you shouldn’t need to use a washer when installing a screw that has a countersunk head.
Pan Head Screws
These woodworking screws are distinguished by a curved head and a flat underside. These screws have a pointy tip that is meant to protrude above the surface of the material.
You can count on a washer being a good fit for these screws. To avoid the screw head digging into the wood, a washer is highly advised when using these fasteners.
Coach Screws/Lag Bolts
Often called “lag bolts,” these screws are of the bigger size. The huge hexagonal head and wider diameter set them apart from standard wood screws.
The head of these screws is meant to protrude from the surface, making them ideal for usage in more demanding construction settings.
Washers are almost always necessary when using coach screws or lag bolts. If you tighten the bolt too much, the washer will keep the head from sinking into the surface.
The hexagonal shape of the head of these fasteners can bind to the fibres of wood, making it difficult to get a good grip and tighten the fastener.
Conclusion – Do Wood Screws Need Washers?
A washer on a wood screw, especially one with a countersunk head, is something I’ve rarely done in all my years of woodworking.
But a coach screw or lag bolt would always get them from me.
With any luck, you’ll be able to use this page as a guide for deciding whether or not to use a washer with a wood screw.
Where Do Washers Go On A Screw?
When using wood screws, the washer is often placed behind the screw head. A washer should be placed under the bolt head and the nut before you tighten them together. In this way, the nuts won’t penetrate whatever is being fastened to them.
Visit this article for further details on the use of washers with bolts.
How Far Do Screws Go In Wood?
It is recommended to drive a countersunk screw just below the surface of the wood while using it.
If you need to know how long a wood screw should be in order to secure two pieces of timber together, that length should be at least double the size of the thickness of the first piece of timber you are screwing into, or at least half the size of the thickness of the bottom piece of timber.
This is a useful rule of thumb to follow, albeit it may not always be achievable. As an illustration, if you are putting together two pieces of wood that are 40 mm thick, the recommended screw length is 80 mm.
Now, obviously, it can’t happen since the screw would go all the way through to the other side of the wood. It’s fine to use a 70 or 75mm screw.
However, the screw’s head can be countersunk with a drill, allowing you to use a smaller screw.