There are many types of screws used in applications that range from construction to small electronics. Some of the most common screw types include flat head screws, round head screws, oval head screws, and truss head screws. Each screw type has advantages and disadvantages depending on the application.
What are Flat Head Screws?
Flat head screws, sometimes called countersunk screws, have a flat top and tapered body beneath the head that allows the screw to sit flush with or counter-sunk into the material. The flat top gives a smooth look compared to other screw types that protrude from the material. The engineers behind SPAX screws explain that most flat-head screw types have a slotted drive, which is driven by a flat-head screwdriver. The key benefit of flat head screws is their ability to sit flush while still providing fastening strength.
Comparing Flat Heads to Round Heads
Round head screws have a dome-shaped top that rises above the material surface. They cannot be counter-sunk for a smooth finish. However, round heads allow better-angled screw-driving access in tight areas. And they have larger bearing surfaces underneath for improved grip strength. Ultimately, flat heads will look better in visible applications where smoothness is preferred. But round heads offer better versatility in terms of driving angle and shear strength.
Oval Heads vs. Flat Heads
Oval head screws are a slight variation on round head screws, with an oval-shaped top. They offer minor aesthetic improvements for visible applications where low-profile heads are desired. But oval heads do not allow for flush mounting like flat head versions. Additionally, oval heads are more specialized and thus harder to find and more expensive than the very common flat-head varieties. For most applications, flat head screws beat oval types on price, availability, and capability to sit flush.
How Flat Heads Compare to Truss Heads?
Truss head screws have very large, flat bearing surfaces combined with shallow domed caps. The large bearing area underneath gives truss heads excellent shear strength for heavy loads. But their wide bearing surface also means truss heads cannot countersink flush. Their domed caps may rise slightly above the material level. So for smooth flush fitting with good strength, flat head screws often surpass truss head types. Nonetheless, if sheer clamping strength is the top concern, truss heads are superior to flat-head varieties.
Choosing the Best Screw Type
With so many screw options available, it can be confusing to select the right type for an application. As discussed above, flat head screws generally provide the best smooth finish of all non-protruding screw types. They also have reasonable availability and cost compared to oval, and truss head variations. However, in situations where strength supersedes appearance, or power tool driving is needed, other screw types can surpass flat head capability. It depends on balancing priorities; finish aesthetics, price, strength needs, installation access, and tool capability must be weighed against the desired function. With a good understanding of strengths per screw type, the ideal version can be selected for virtually any job.
Conclusion
While flat head screws have definitive advantages for flush fitting applications, they also have limitations in terms of strength, driving access, and tool compatibility found with round, oval, or truss head alternatives. There is no universally “best” screw type. The ideal selection depends on balancing smoothness needs with shear strength capability, pricing, availability, and intended tool installation method. After assessing the application priorities involved, flat head screws will often prove optimal for lighter-duty settings where an unobtrusive recessed finish is desired. But varied applications may benefit from capabilities uniquely offered by other screw head configurations.