Rivet Nuts in Sheet Metal: Press-in, Clinch, and Pull-in Nuts — Still Confused?
1. Press-in (Staking) Rivet Nuts
Press-in riveting (also called staking or swage riveting) involves pressing the rivet nut into a preformed cavity or slot in the base material. Under external pressure, the rivet nut causes plastic deformation of the surrounding metal, locking itself securely in place.
There are two main types of non-standard press-in nuts:
- Press-in rivet nut studs
- Press-in rivet nuts
Key points:
- The hardness of the rivet nut must exceed the hardness of the base material for reliable fastening.
- Suitable for low-carbon steel, aluminum, and copper sheet.
- Not ideal for stainless steel or high-carbon steel, as these are harder materials. Using standard press-in nuts on stainless steel often leads to difficult installation, weak bonding, and easy detachment. Manufacturers sometimes resort to welding the side of the nut stud to ensure reliability, which complicates the process and increases costs.
- Press-in screws and nuts share similar limitations: they generally should not be used on stainless steel sheet metal.
Illustration:
Figure 1 — Press-in riveting process diagram
2. Clinch (Expansion) Rivet Nuts
Clinch riveting works differently. During installation, part of the rivet nut plastically deforms under applied force to form a tight fit with the base material.
Characteristics:
- Simple process, easy to implement.
- Strength is moderate — not ideal for high-torque applications.
- Often used in applications where installation space is limited and the torque load on the fastener is not critical.
- Common examples: ZRS-type expansion nuts.
Illustration:
Figure 2 — Clinch riveting process diagram
3. Pull-in (Blind) Rivet Nuts
Pull-in riveting (commonly known as blind rivet nut installation) uses a special rivet gun to deform the rivet nut axially. The deformation occurs in a specifically designed section, clamping the base material securely.
Key points:
- Ideal for tight installation spaces where conventional rivet tools cannot fit, such as inside closed tubes or enclosures.
- Provides strong, reliable fastening in blind-hole applications.
- Requires specialized rivet tools for installation.
Illustration:
Figure 3 — Pull-in riveting process diagram
4. Comparative Overview
| Feature | Press - in (Staking) | Clinch (Expansion) | Pull - in (Blind) | Threaded Through - hole (Tap) |
| Installation method | Pressing into preformed slot | Deforming around base material | Axial deformation with rivet tool | Direct tapping |
| Material suitability | Soft metals (Al, Cu, low - carbon steel) | Medium - hard metals | Thin/limited access materials | Any, depending on tap |
| Strength | High if base softer than nut | Moderate | High for blind applications | Very high (full thread engagement) |
| Tool requirement | Pressing machine | Simple press or hand tool | Special rivet gun | Drill & tap |
| Space requirement | Needs access to nut backside | Accessible surface needed | Minimal, can work in closed sections | Full through - hole needed |
| Rework & replacement | Difficult once pressed | Can be pried out with care | Removable but tool needed | Easy to replace if tapped properly |
| Typical applications | Consumer electronics, light panels | Automotive interior trims, low - torque panels | Enclosures, tube structures, compact assemblies | Heavy - duty machinery, structural components |
Practical Tips
- Choose press-in nuts for quick assembly on softer sheet metals where production volume is moderate. Avoid stainless steel unless using high-strength custom nuts.
- Clinch nuts are your go-to for simple, low-torque connections where you don’t need premium strength. Installation is quick and inexpensive.
- Pull-in nuts are ideal for blind or hard-to-access areas, providing reliability where other methods fail.
- Through-hole tapping remains the gold standard when maximum strength and repeatability are needed, but it requires full access and careful machining.
5. Conclusion
Understanding the differences between press-in, clinch, and pull-in rivet nuts is crucial for reliable sheet metal assembly. Choosing the wrong type can lead to weak connections, production delays, or increased costs.
Press-in rivet nuts: fast and strong, but limited to softer metals.
Clinch rivet nuts: simple, moderate strength, easy to implement.
Pull-in rivet nuts: flexible, blind-hole compatible, reliable in tight spaces.
Through-hole tapped holes: maximum strength, ideal for heavy-duty applications.
By mastering these distinctions, engineers and designers can ensure secure, efficient, and cost-effective sheet metal fastening, avoiding common pitfalls and optimizing assembly performance.