The NAS test evaluates looseness prevention as determined by US aerospace standards. The testing apparatus prepared for the test is shown at right.
The standard test method for metric fasteners is stipulated by NA0009, and the testing apparatus is established in NAM1312-107. The standard test method for unified fasteners is stipulated by NAS3350, and the testing apparatus is established in NAS3354.
Stipulated Test Procedure
1: Attach and remove the nut four times. Attach a fifth time, tightening with the set torque. 2. In an electric oven, heat the testing device (with the fastened nut) to 800 ± 25° F (425 ± 2° C) or to 450 ± 25° F (230 ± 2° C). 3. After heating, apply a machine oil such as an SAE oil and tighten. 4. Mark the bolt, the nut and the washer and begin the shock test. 5. Carry out vibration at a frequency of 1750–1800 cpm for 30,000 cycles (approximately 17 minutes), and a make a determination of pass or fail on the basis of whether the bolt gap is less than 360°.6. After the test is complete, examine the nut under 10× magnification for cracks and breaks.
The Hardlock Nut has been demonstrated to have an excellent looseness prevention effect.
Test nutsSN: Hex nutSN+SW: Hex nut + spring washerWN: Hex nut + hex jam nutHLN: Hardlock nut