Screws and bolts are threaded fasteners designed to mechanically join materials. Defined by their helical threads and head configurations, these components enable removable or permanent assemblies in engineering applications. Their importance in modern technology stems from their ability to provide high clamping forces, ease of installation, and adaptability across industries ranging from aerospace to consumer electronics.
| Type | Functional Characteristics | Application Examples |
|---|---|---|
| Hex Bolt | High torque transmission, hexagonal head for wrenching | Structural steel connections in construction |
| Socket Head Cap Screw | Internal hex drive, cylindrical head for precise torque | Machinery assemblies requiring flush mounting |
| Self-Tapping Screw | Drills own thread in mating material during installation | Metal sheet joining in HVAC systems |
| Carriage Bolt | Dome head with square neck to prevent rotation | Wood-to-metal fastening in furniture |
| Anchor Bolt | Expandable end for concrete substrate anchoring | Foundation connections in industrial equipment |
Typical configurations include: - Head (hexagonal, cylindrical, or countersunk) - Bearing surface (under-head contact area) - Shank (unthreaded cylindrical section) - Threaded portion (metric or imperial pitch) - Point (tapered or blunt end) Materials range from carbon steel (grades 4.8-12.9) to stainless steel (A2/A4), titanium, and specialty alloys. Surface treatments include zinc plating, galvanization, and phosphate coatings.
| Parameter | Significance |
|---|---|
| Tensile Strength (MPa) | Determines maximum axial load capacity |
| Proof Load (MPa) | Maximum stress before plastic deformation |
| Hardness (HV/HRC) | Indicates wear resistance and brittleness |
| Thread Pitch (mm/TPI) | Dictates engagement quality and assembly speed |
| Corrosion Resistance Class | Measured by salt spray test hours (e.g., ISO 9227) |
| Manufacturer | Key Products |
|---|---|
| Hilti Corporation | HIT-HY 150 MAX adhesive anchors |
| Bossard Group | Delta PT self-tapping screws for aluminum |
| Stanley Black & Decker | FASTORQ structural hex bolts |
| ARaymond | Push-on quick-connect fasteners for automotive |
Key considerations:
Example: Selecting A4-70 stainless bolts for coastal infrastructure projects ensures seawater resistance while maintaining 700MPa tensile strength.
Current developments include: