Screws play an important role in countless consumer and commercial products. With their threaded body, they are able to hold parts together. Driving a screw into a set of objects will create a compressive force. The screw will essentially squeeze the adjacent material, thereby holding the parts together. There are many different types of screws, however, including undercut.
What Are Undercut Screws?
Undercut screws are mechanical fasteners with a shorter head that’s not fully conical. If you inspect the area below the head, you’ll notice it has a shorter neck section. This is the section that connects the head to the body. With a shorter neck, undercut screws perform differently than other types of screws.
You can find undercut screws in different drive types, some of which include the following:
- Phillips
- Slotted
- Six-point
- Square
- Combination
Undercut vs Traditional Countersunk Screws
How do undercut screws differ from traditional countersunk screws exactly? While they both have a tapered neck, they aren’t the same. Undercut screws feature a shorter head with a truncated neck. Roughly one-third of the bottom of the neck is removed or “cut,” which is why they are known as “undercut screws.”
Undercut and countersunk screws generally have the same taper angle, such as 82 or 100 degrees. Undercut screws simply have a shorter head and neck because they are truncated.
How Undercut Screws Work
The reduced neck height of undercut screws allows for superior head contact when used in conjunction with a shallow countersunk hole. During installation, the head won’t bottom out early, nor will it push into adjacent material. This is particularly important when working with thin or fragile materials, such as wood or sheet metal.
If a material is thin or fragile, the head of a screw may damage it. As you drive the screw into the material, the neck may dig into it. Undercut screws offer a solution. They have a shorter neck than traditional countersunk screws, allowing them to fasten thin and fragile materials without damaging them.
The undercut section below the head is shallow and flattened. This design reduces the total height of the head. If you’re worried about damaging thin or fragile materials, or if you simply want a more low-profile design, you may want to choose undercut screws.
In Conclusion
Undercut screws may look like ordinary mechanical fasteners, but their shortened head and reduced neck sets them apart. They are able to make better contact with shallow countersunk holes while reducing the chance of the screw damaging thin or fragile material. With several drive styles available, undercut screws offer a practical fastening option for specialized applications.