Selection must be based on the core needs of the application environment. The aerospace field faces extreme temperature differences and pressure fluctuations; titanium alloy flush nuts are the first choice due to their tensile strength of over 800MPa and lightweight properties, which can maintain stable performance in the temperature range of -50℃ to 150℃.
Medical devices have extremely high hygiene standards; 316L stainless steel exhibits excellent corrosion resistance, withstanding repeated treatments such as steam sterilization and chemical disinfection, while also possessing good biocompatibility. In the vacuum environment of semiconductor manufacturing, zirconia ceramic nuts demonstrate ultra-low volatility, with a friction coefficient of only 0.15, preventing chip scrapping caused by particle contamination.
Specification matching must strictly comply with tolerance standards: thread dimensions should maintain a fit accuracy of H7/g6, and common specifications (M3-M20) must be selected based on load calculation. Under composite working conditions, the safety factor should be no less than 1.5; for example, structures bearing combined axial and shear forces require finite element analysis to verify the stress stability of the nuts.
Pretreatment before installation directly determines connection quality. The connection surface must be ultrasonically cleaned with anhydrous ethanol (power: 500W, duration: 10 minutes) to remove micron-level oil stains and oxide layers, ensuring a surface roughness of Ra ≤ 1.6μm. Thread inspection requires using thread gauges with an accuracy class of 4H/5g for go-no-go testing, and the thread angle error must be controlled within ±0.5°—otherwise, installation jamming may occur.
Tool preparation must be professional and standardized: torque wrenches should comply with ISO 6789 standards, with an accuracy class of ±3%, and be calibrated by a metrology institution before use. For operations in narrow spaces, magnetic sockets or flexible drive shafts can be equipped to avoid thread damage caused by incorrect operation angles.
During the manual pre-tightening stage, vertical coaxiality must be maintained, and the screwing speed should be controlled within 10r/min. After the nut is screwed in 3-5 threads, a 0.02mm feeler gauge is used to detect the end face gap to ensure no deviation. The tightening process adopts the stepped torque method: first apply 50% of the rated torque, pause for 30 seconds to allow full thread deformation, then apply torque to 100% of the rated value.
Torque parameters vary significantly among different materials: for M8 titanium alloy nuts, the recommended torque is 25-28N?m; for stainless steel nuts, it requires 30-32N?m; for ceramic nuts, it should be controlled at 18-20N?m to prevent brittle fracture. After tightening, a dial indicator is used to detect end face flatness, with an allowable error of ≤0.01mm/m, ensuring the true "flush" effect is achieved.
After installation, 3D coordinate inspection is conducted to confirm the connection position error is ≤0.1mm. Dynamic testing simulates equipment operating conditions, performing 1000 cycles of vibration tests (frequency: 10-2000Hz) to monitor the preload attenuation—the qualification standard is no more than 10% of the initial value.
Differentiated maintenance cycles must be established: inspection every 3 months in humid environments, and extended to 6 months in dry environments. When slight thread rust is found, polish it with fine sandpaper (800 grit or higher), then apply molybdenum disulfide grease. When replacing nuts, the hot disassembly method (heating to 120℃) is adopted to avoid thread damage caused by cold disassembly.
Through scientific selection, standardized installation, and regular maintenance, the service life of flush nuts can be extended by more than 30%. In practical applications, parameters must be dynamically adjusted based on specific working conditions; for example, in high-temperature environments, molybdenum-containing high-temperature alloy materials should be selected to ensure long-term reliability of the connection system.
