When you set out on your latest project, you need to ask yourself if you should use nails vs. screws in the construction. Each one has its own benefits and shortcomings for different applications, so it’s best to know which is right for the job. Choosing the wrong one can mean your whole project will fall apart, while the right application will spell sturdy and reliable for whatever you’re constructing.
The Two Main Concepts
When dealing with the question of when to use nails or when to use screws, there are two concepts you need to take into consideration: grip strength and shear strength.
Grip Strength
Grip strength is the ability to fasten material together. For this example, we’ll use wood. A fastener that uses grip strength keeps two pieces of wood from separating, typically when the force is vertical.
Shear Strength
Shear strength is the ability to handle the force coming from the sides of the wood to keep them from shifting out of place. Shear strength works best on a horizontal plane.
Nails
Now that we know the two concepts, we can dive into which fastener is the best tool for which job. Nails are most ideal for projects that have shear strength. Nails bend in response to pressure, but they rarely snap as a result of it. This kind of flexibility can be seen in hog rings, another fastener with its own applications. With force applied from hog ring pliers, a nail can be bent into a full circle without breaking.
Why Screws Won’t Work
Screws cannot handle being bent. If shear force was applied to a screw, then it would break.
Screws
As you may have guessed, screws are more suited for grip strength rather than shear. Screws will keep the wood secure when vertical force is applied, far greater than a nail could support. By the design of the screw, it draws the two wooden pieces together, fastening them together with the thread of the screw holding them tightly in place.
Why Nails Won’t Work
Nails aren’t ideal for the job of grip strength simply because they can be relatively easy to pull apart. Because a nail doesn’t have a thread like a screw does, if vertical force was applied then the wood would slip off.
Right Fastener for the Job
When you should use nail vs. screws depends on what kind of force you are working against. Shear force is horizontal force and needs nails, while grip force is vertical and needs screws.