Solid Rivets For Permanent Fastening

Strong Rivets Beat Bolts and Welds

 

 Before we discuss solid rivets, let's be honest about when they're best and when they're not.

Why bolts occasionally fail-not their fault

Bolted joints use clamp load. Correct torque locks the joint. That clamp load decays in real-world assemblies including robotics arms, outdoor enclosures, and transport equipment. Vibration does it. A thermal cycle does it. Just time does it. The joint micromoves and fatigues when preload goes below a threshold. Bolted joints in dynamic applications weaken due to preload loss.
Solid rivets eliminate this failure mode. No decaying clamp load. Mechanical and geometric joint integrity-the upset shaft fills the hole and maintains interference fit independent of environment.

Why welding isn't always feasible

Strong permanent joints are made by welding. It requires certified welders, creates heat-affected zones (HAZ), and is impracticable for dissimilar metals, thin-walled sections, or field-serviced assemblies. Solid rivets provide a permanent bond without heat, distortion, or the requirement to access both sides (unlike most weld designs).

 Engineers should specify solid rivets first if the connection will never need removal, the environment is corrosive, and the assembly contains different metals or thin portions.

How a Solid Rivet Actually Installs

I find that most engineers know that solid rivets are "deformed to fasten," but fewer have thought through what that deformation actually does to the joint. Understanding the mechanism matters for specifying the right rivet and the right hole tolerance.

The four stages of rivet setting

• The rivet (manufactured head + smooth shank) is placed in a pre-drilled hole. Hole diameter must be slightly larger than the rivet shank - typically 1.0–1.5% larger.
• The setting tool grips the manufactured head on the blind side. The tail (protruding end) is positioned in the anvil.
• Compressive force is applied. The rivet tail shortens and expands radially, filling the hole and creating radial pressure against the hole wall. The manufactured head draws the sheets together.
• Once set, the shank is larger than the original hole. The resulting frictional and mechanical interlock is the source of the joint's shear and tensile strength.

The key insight here: hole preparation is as important as the rivet itself. An oversized hole means insufficient upset; an undersized hole prevents proper deformation. At KEY-CNC, we specify hole diameters with our rivet shipments, and we can machine custom shank diameters to match non-standard hole sizes in your assembly.

What Actually Kills a Riveted Joint

This is the section I wish more design engineers read before they specify their last riveted assembly. Understanding failure modes is the fastest path to the right specification.

Shear vs tension: knowing which load case matters

A riveted joint in single-shear carries load on one cross-section of the rivet shank. In double-shear, two cross-sections share the load. For most structural applications, solid rivets are specified for shear loading. Tensile loading on a riveted joint tends to separate the sheets at the joint line - if your design sees significant tensile loads, consider a thicker sheet, a larger rivet, or an additional fastening method.

Four failure modes you need to check in your design

• Rivet shear failure: the shank is loaded beyond its shear strength.

Fix: use a larger rivet diameter or a higher-strength material.

• Sheet bearing failure: the rivet hole ovalises under load, especially in thin or soft materials.

Fix: increase sheet thickness, use a washer under the manufactured head, or select a material with higher bearing strength.

• Sheet tearing: the sheets pull apart around the rivet, especially near the edge of the joint.

Fix: increase edge distance - the distance from the rivet centre to the free edge of the sheet should be at least 2× the rivet diameter.

• Rivet sidling (bending): eccentric loading causes the rivet to bend rather than shear cleanly.

Fix: improve joint symmetry, add backing plates, or use a larger rivet.

Quick check: For most structural aluminium assemblies, the minimum recommended edge distance is 2d (2× rivet diameter) for the near edge and 1.5d for the far edge. Always verify against your specific material and load case. 

Choosing the Right Material for Your Application

Material selection for solid rivets is where a lot of engineers either over-specify (and overpay) or under-specify (and wonder why the joint corroded after six months). Let's cut through that.

A note on anodizing for aluminium rivets: it adds a 25–50 μm aluminium oxide layer that significantly improves corrosion resistance and surface hardness. If your assembly will be wiped down with solvents or exposed to humid environments, specify Type II anodizing alongside your 2017-T4 or 7075-T6 rivet. KEY-CNC provides in-house anodizing as part of our one-stop precision manufacturing service.

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