When you start looking for fastening solutions at Bossard, you’ll notice that we carry a diverse variety of screws and bolts. One way to distinguish one from the other is through the type of head that they have. The following are some of the most common styles. While head styles do have a specific purpose in creating a mechanical joint, you can find out which is most appropriate for your assembly by contacting your local Bossard agent.
Countersunk Screw Heads
If a screw has angles under the head, it demands countersinking to prevent the wood from splitting during drilling or other force. Countersunk screw heads include the following:
- Flatheads sit flush against the surface of the material being screwed, which makes for a cleaner appearance and prevents anything from being caught on them. If you’re fastening wood or plastic laminate components, a screw cover hides the head completely.
- Roundheads, which are also called raised screw heads, use angles similar to that of flat heads, so they require countersinking. Their domed heads look decorative, so they are used where appearance is important, such as for switch covers. Roundheads that are designed for a socket drive are called button heads.
- Bugle heads reduce damage to material by spreading the joint stress over a broader surface than flatheads. They’re used mostly for plasterboard, wood decking, and drywall. They are self-drilling, which means they compress the surrounding drywall and paper to create a countersunk hole during drilling.
Both flat and round heads generally demand a pilot hole, which is a small hole drilled to guide the main screw in.
Non-Countersunk Screw Heads
Non-countersunk screw heads are the most common type and have flat surfaces under the head, which avoids countersinking. They are fully exposed above the surface of the material being screwed.
- Domed heads have a rounded head that adds aesthetic appeal to a product.
- Button heads also have a round design but are used with socket-driven screws and Torx drive recesses.
- Pan heads are the most common type of flat-bottomed screw. They are versatile enough to substitute for other round styles.
- Fillister heads use a slightly rounded top with a small diameter on high cylindrical sides. Their higher profile requires a deeper drive slot than round or pan head screws.
- Truss heads are wider and slightly rounded to produce a lower profile and larger bearing surface. They are useful for sheet metal joints.
- Hex heads allow for more torque and demand a socket or wrench for installation.
- Socket cap heads require socket drive recesses for flush installation against the surface. They deliver a smooth appearance despite being non-countersunk.
- Square heads are found in bolts and screws. They require a wrench for installation.
Some bolt heads have shapes that are similar to screw heads, such as flat, round, truss, and hex. Unique types include the carriage bolt, which uses a rounded dome with a square underside, anchor bolts, which do not contain a head, and J and U bolts, which look like their namesakes.