A German manufacturer of portable patient monitors was designing a new 7-inch touchscreen model with an extremely compact internal layout. The front housing was made of 1.2mm aluminum sheet. On the back side of this front panel, a main PCB was positioned only 2.5mm away. Standard M3 press nuts would protrude approximately 3.0mm behind the panel, colliding with the PCB. The client needed a solution that provided full clamping strength without intruding into the limited internal space.
The Challenge
The client had previously tried two approaches. First, they attempted to use shorter standard press nuts, but those had insufficient thread length, resulting in low pull-out strength during assembly testing. Second, they considered designing a cutout in the PCB to clear the protruding nut, but that would compromise board layout and signal routing.
They approached several European fastener distributors, but none offered custom thread lengths for small batches. Their minimum order quantities started at 5,000 pieces—far above the 300 pieces needed for initial production.
Our Solution
Tingfeng Hardware reviewed the assembly 3D model and panel thickness specification. We proposed a custom M3 press nut with a reduced thread length of 3.2mm. The standard M3 press nut has a thread length of 5.0mm, which would protrude 3.8mm behind a 1.2mm panel. By reducing the thread length to 3.2mm, the nut would protrude only 2.0mm, safely clearing the PCB positioned 2.5mm away.
To maintain pull-out strength despite the shorter thread, we used a higher-strength 304 stainless steel and optimized the clinching profile to maximize engagement. The custom tooling was designed in-house and completed in 6 days.
Results
50 samples delivered within 48 hours for fit testing.
Samples installed flush with the back of the panel, providing 0.5mm clearance to the PCB.
Pull-out force tested at 420N, exceeding the client’s 300N requirement.
300-piece production completed in 10 days with 100% thread gauge inspection.
Client Feedback
"Tingfeng‘s custom thread length press nuts solved our internal clearance problem without requiring a PCB redesign. The 48-hour samples allowed us to validate the fit immediately. We have since standardized on their custom-length nuts for two additional product lines." — Dr. Markus Bader, Mechanical Engineering Manager, MedMonitor GmbH