A Guide to Screws, Bolts, and Their Uses

Screws and bolts are essential fasteners used to hold parts together tightly during the assembly and installation of products and building structures. They are ubiquitous in everyday life, found in everything from machinery assembly and automotive parts to electrical appliances and wooden furniture.

Generally, screws and bolts are threaded metal rods featuring a head fitted with grooves (the drive) to allow for tightening with a screwdriver or wrench. They can be used for both permanent and temporary fastening. They are manufactured in a wide variety of shapes, sizes, thread types, and materials—ranging from standard steel to durable, rust-free stainless steel—to meet the needs of any application.

While screws and bolts may look similar, they serve different purposes depending on the application and how they engage with the materials being fastened.

Screws	Screws are typically used to fasten objects into "blind" or solid holes where access is only available from one side. The screw threads directly engage with the workpiece material (creating its own threads in wood or plastic) or are used in conjunction with a wall plug for masonry. They are suitable for fastening steel sheets, gypsum boards, frames, and various wood structures.
Bolts	Bolts are designed to fasten through-holes, passing completely through the workpieces. They do not rely on threads in the workpiece itself; instead, they are secured on the other end with a female nut to clamp the structure together tightly. They are suitable for heavy-duty structural fastening in vehicles, machinery, and molds. Some bolts also serve as lifting or hanging points for heavy objects.

Screws are generally divided into six main categories based on their design and application.

Hex Socket Head Cap Screws	These screws feature a cylindrical head (which can be high or low profile) with an internal hexagonal hole. This design allows for high clamping force when tightened with a hex wrench (Allen key) Note: Some versions have tapered countersunk heads to sit flush with the surface, used commonly in automotive parts, machinery, and electronics.
Self-tapping Screws or Wood Screws	These screws have long threads and sharp, pointed tips designed to screw directly into wood or plastic without needing a pre-drilled hole or a matching nut.
Machine Screws	Designed with high-precision, fine threads, machine screws are used to fasten metal parts together securely. They are tightened into tapped holes or used with nuts and are less prone to loosening over time compared to coarser thread types.
Self-Drilling Screws	Often called "Tek screws," these feature a tip that resembles a drill bit. This allows the screw to drill its own pilot hole and tap its own threads in a single operation, eliminating the need for pre-drilling.
Set Screws	Set screws are threaded along their entire length and typically have no protruding head. Instead, they have an internal hexagonal drive in the top to be tightened into a workpiece against a shaft using a hex wrench. They come with various end types—flat, cylindrical, pointed, cup, or rounded—and are used in machinery, automotive assemblies, and molds to secure rotating parts like pulleys or gears to a shaft.
Screws with Captured Washer (SEMS Screws)	These screws feature a pre-attached washer (either plain flat or spring type) under the head that spins freely but cannot fall off. This integrated washer helps distribute fastening force, prevents damage to the workpiece surface, and increases clamping firmness. They are available with various drive styles like Phillips or hex.

Bolts generally fall into five main categories.

Hexagonal Head Bolts (Hex Bolt)	The most common type of bolt, featuring a six-sided head. They are available in standard styles or with integrated flanges and are used for a wide range of temporary or permanent fastening jobs.
Stripper Bolts (Shoulder Bolts)	These bolts have a round head with an internal hexagonal drive. Below the head is a smooth, unthreaded cylindrical shoulder, followed by threads at the bottom tip. When installed, the smooth shoulder acts as a shaft or pivot point, allowing moving parts to rotate or slide along its length. They are commonly used in tool and die making to guide stripper plates.
Stud Bolts (Threaded Rods)	Stud bolts are metal rods threaded along their entire length with no head. They are high-strength fasteners capable of withstanding significant shock and vibration. They are used with nuts on both ends, making assembly and disassembly easy. Common uses include concrete structural fastening, hanging pipe systems, and ceiling installations.
U-Bolts	Shaped like the letter "U," these bolts are designed for clamping, hanging, or fastening round objects like pipes or conduit. They are used in conjunction with a metal plate and two nuts.
Specialty Bolts (Eye, J, L Bolts)	Beyond standard fastening, some bolts are designed for specific functions. For example, Eye Bolts have a looped head used for lifting and moving heavy objects, while J-bolts and L-bolts are often used as anchor bolts in concrete.

Screw heads can be categorized by their external shape (profile) and the type of tool required to drive them (the notch or recess).

Common Drive Types (Notch):

• Phillips and Frearson (Crosshead)
• Slotted (Flathead)
• Combination (e.g., Slotted/Phillips)
• Socket, Hex, or Allen
• Square (Robertson)
• Torx (Star)
• One-way (Security)

Common Head Shapes (Profile):

• Flat head
• Pan head
• Round head
• Oval head
• Truss head
• Button head
• Hex head
• Hex washer head
• Socket cap

To function correctly, screws and bolts often require complementary hardware.

Nuts	Nuts: Fastening devices shaped like hexagonal rings with internal threads, designed to mate with bolts to secure materials together.
Washers	Washers: Flat or spring-loaded rings placed under a bolt head or nut. They distribute the fastener's load over a wider area, protect the surface, and improve grip.
Retaining Rings (Snap Rings)	Retaining Rings (Snap Rings): Fasteners used that snap into a groove on a shaft or in a bore to lock components in place and prevent them from sliding apart.
Anchors	Anchors: Devices used to provide a secure grip point for screws or bolts when fastening into brittle or hollow materials where a thread cannot hold on its own, such as drywall, concrete, or brick walls.

Selecting the right screw or bolt is critical to ensuring strength, safety, and long-term performance. With MISUMI’s wide range of precision fasteners, clear specifications, and reliable quality, engineers can confidently choose the right solution for any application—streamlining design, assembly, and productivity.