The side hole design of the extended nut is based on precise calculation of the interference relationship between the hole position and the thread (typically the hole diameter is 1/3-1/2 the thread diameter, e.g., an M12 nut corresponds to a 4-6mm hole). This ensures that the nut's strength is maintained (tensile strength maintains grade 8.8 or 10.9 standards) while also achieving the following functions:
- Anti-loosening function: The side hole can be inserted with a cotter pin or wire lock, suitable for vibrating environments (e.g., when fixing agricultural machinery shafts, anti-loosening efficiency is increased by 60% at vibration frequencies >15Hz).
- Lubrication channel: In mining machinery, the side hole serves as an oil injection port (recommended oil injection pressure of 0.2-0.5MPa), extending thread life by more than three times.
Materials and Processing
Cold heading (accuracy ±0.1mm) or CNC machining (costlier but suitable for special materials such as titanium alloys) are used. The surface is galvanized (thickness 5-8μm) or Dacromet-treated (salt spray resistance >500h). II. Typical Application Scenarios and Selection Guide
1. Heavy Equipment
- Wind turbine tower bolt connections: Using an M30 extended nut (6mm side hole) with a hydraulic tensioner, the preload can reach 450kN (referring to IEC 61400-6).
- Railway rail fasteners: The side hole design allows for lateral insertion of an elastic pin, increasing lateral displacement resistance by 40%.
Advantages Compared to Traditional Nuts
1. Functional Scalability
While conventional nuts rely solely on friction to prevent loosening, extended side hole nuts use mechanical locking (e.g., a pin) to reduce the risk of loosening to <1% (laboratory vibration table test results).
2. Ease of Maintenance
In oil pipeline flange connections, the side hole design allows for direct oiling and cleaning without disassembling the nut, saving over 50% maintenance time.