Full thread vs part thread screws
Not all screws look the same or serve the same purpose (although it would be much easier for us if they did).
When it comes to choosing the right screw for the task at hand, the type of thread it has is one of the most important factors. Why? The thread type affects how well it grips the material and how smoothly it drives into the surface.
Choose the wrong one, and you could end up with cracked surfaces and loose screws. Today, ASP will delve into the primary differences between fully threaded and partially threaded screws and when to use each one.
Whether you’re undertaking a DIY task or need to stock up your toolbox for work, we provide a range of high-quality, rust-resistant screws suitable for both outdoor applications and indoor assemblies. The best part? All of our prices start low.
Quick pick
Do you want to skip the long-winded explanations? If you’re just looking for a straightforward answer to which type of thread you need for your job, then we’ve got you covered:
- Select a full-thread screw when you require maximum bite along the entire shank (e.g., fixing a thin sheet to timber or driving into plugs).
- Pick a part thread screw when you need to draw two pieces tight together (the plain shank under the head acts like a clamp and helps alignment; it’s better when issues like side-loading and shear occur).
What is a full-thread screw?
With a full-thread screw, the clue is in the name. The thread, or helical ridge, runs from the tip of the screw to the underside of the screw head.
Unlike a part-thread screw, which has a smooth section under the head, full-thread designs don’t have any plain shank at all, providing a precise drive into the material. That continuous thread provides maximum grip, helping to distribute the load easily and reducing the risk of loose installations.
For this reason, they’re mostly used for sheet materials, MDF, plywood, or fixing screws into plugs.
What is a part-thread screw?
Since we now know that full head screws have threads that run along the full length of the screw, you’d be correct to think that part-thread screws have threads that only run along half the length of a screw.
It consists of two main parts: a threaded portion at the tip and a smooth, unthreaded shank that extends up to the underside of the head. When driven into a surface, the plain shank helps the top piece of the material slide down without catching on threads.
The result includes a strong clamping action, as the screw draws the top layer tightly against the one below, creating a secure fit. That’s why partly threaded screws are popular for framing, decking, and joinery, since they pull two materials together tightly without a gap.
Grip vs clamp vs shear: what do they mean?
So, when it comes to choosing between a full thread or a part thread screw for your project, three main forces come into play: grip, clamp, and shear. Understanding what each one means and how to look out for them will make the final decision much easier!
Grip (pull-out resistance)
The grip of a screw is in reference to how well it attaches and stays in a material, such as installing a screw into a wooden table.
Full-thread screws often provide better grip, which is important for installations where a tight grip is necessary, since the thread runs along the entire length of the shank, spreading the load evenly.
This matters when you’re:
- Securing sheet materials where pull-out is the main risk
- Fixing into wall plugs in masonry
- Working with softer woods
Clamp (holding materials together)
When you hear the word clamp, it means how well a screw can hold two different pieces or materials together.
A part-thread screw is often the winner here, as the plain shank allows the top piece of material to slide freely as the screw is driven; the head bears down and pulls the top piece securely against the bottom.
This is especially helpful for:
- Joinery and carcassing, where gaps can weaken the joint
- Decking boards, as it reduces squeaks and movement
- Framing jobs where alignment is key
Shear (side-load strength)
When weight or pressure pushes sideways across the screw, shear force occurs.
For this, having a thicker core of metal where the highest stress occurs on the surface makes the screw less likely to snap or deform under load. That’s why part-thread screws perform better as it’s more resistant to bending.
Shear resistance is especially important in:
- Studwork and framing where screws take side pressure
- Outdoor frames, fences, and pergolas that are exposed to harsh winds
- Heavy-duty joinery, such as staircases or beams
Making a final decision
If you’re looking for something that aligns easily for applications where precision is needed, then part-thread screws are a go-to.
Many people use these for fixing a joist to a beam or assembling furniture, where accuracy matters, as the plain shank prevents the material from getting stuck while driving in. However, since part-thread screws come in a variety of thread lengths, the size of the screw matters.
All you need to ensure is that the threaded part of the screw passes into the second piece of the material all the way. Shorter screws may have a smaller threaded section, while longer screws often have a larger plain shank for clamping strength.
Full-thread screws, on the other hand, are perfect for thin or layered materials, such as screwing into cladding panels, or attaching sheet material to timber battens. The full thread design grips every layer it passes through for a secure hold, leaving no “dead space” in the joint.
These often have self-tapping or self-cutting tips for a quick installation, perfect for tasks that need to be completed swiftly.
Browse full and part thread screws at ASP today
No matter what type of thread, length, or screw you need for your next project, we’ve got it at ASP Ltd for prices you won’t be able to resist.
Our bulk screws are ideal for those who need to stock up for one or multiple projects in one go, with a selection of wood screws, concrete screws, chipboard screws, and plenty more to browse.
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