NAS 3350 (National Aeronautics Standards) screw loosening tests
NAS3350 is a premier technical standard originally developed for the American aerospace and space industries. It defines the rigorous requirements for high-quality Self-Locking Nuts capable of maintaining peak performance in extreme high-temperature environments—ranging from 450°F (approx. 232°C) up to 800°F (approx. 427°C).
Today, its application extends far beyond aerospace. It has become the global benchmark for evaluating anti-loosening performance in sectors where absolute reliability is non-negotiable, including railways, bridge construction, automotive engineering, and heavy industrial machinery.
The Gold Standard of Testing: NAS Vibration Test
The core of this standard lies in the NAS-type Accelerated Vibration and Shock Test (often referred to as the NAS Vibration Test). This procedure subjects the bolted joint to simultaneous, high-intensity impact and vibration, ensuring the fastening solution remains secure under the most punishing conditions.
Test overview
■ Purpose
To perform a screw loosening test based on NAS (NATIONAL AERO SPACESTANDARD) 3350 [US aviation standard 3350].
■ EUT
Bolts, nuts
■ Test conditions
(1) Vibration frequency: 30 Hz (1750 – 1800 cpm)
(2) Amplitude: 11.43 mmp-p (11.43 ± 0.381 mmp-p)
(3) Vibration frequency: 30000 cycles (approx. 17 minutes)
(4) The bolt and nut were fastened by attaching a collar and a washer in a slotted hole in the test fixture.
At this time, tighten with the specified torque.
Attach the test fixture with the bolt and nut fastened to the vibration table, and mark the bolt and nut.
■ Other
The test was carried out in the presence of the customer. The vibration table controls the above test conditions using a laser displacement meter. After the test was completed, the condition of the bolts and nuts ware checked by the customer (for looseness or damage) and the test was completed.
*The pre-treatment specified in NAS 3350 was not carried out.
*Tests had been carried out for M6 to M27.
*Up to three pieces can be shaken simultaneously at one time (up to M22). About four tests can be carried out in half a day.
Test image
Memo
Facilities used
Vibration test system: i240/SA3M/H6
Vibration controller: K2 software Sine
Head expander: TBV-550S-i20-M
Test time
3 hours/half day
About Our Contract Testing Services
IMV CORPORATION operates 10 ISO/IEC 17025 accredited independent laboratories globally. Our expert staff provides comprehensive support for the reliability evaluation of all products—including automotive, railway, aerospace, electronics, and marine—delivering impartial, internationally recognized data.