What "Holding Strength" Actually Means for Rivet Nuts

When people ask how many pounds a rivet nut can hold, the answer depends on which type of load you're talking about. Rivet nuts — also called nutserts, blind rivet nuts, or threaded inserts — can fail in three distinct ways, and each has its own strength rating. Understanding the difference is the first step to using rivet nuts correctly and safely.

Pull-out strength (also called tensile strength) is the force required to yank the rivet nut straight out of the base material in the axial direction — essentially pulling it through the hole. This is the most commonly referenced load rating because it's the most straightforward failure mode to test. Shear strength is the resistance to a lateral force applied perpendicular to the rivet nut's axis — the kind of load that tries to slide the fastener sideways through the material. Torque-out strength is the rotational resistance — how much turning force the installed rivet nut can handle before spinning in the hole. In most real-world applications, the actual load is a combination of all three, but pull-out strength is the primary benchmark used by manufacturers for load ratings.

Rivet Nut Load Capacity by Size and Material

The two biggest variables in rivet nut holding strength are thread size and the material the rivet nut itself is made from. Here's a practical breakdown of typical pull-out and shear strength figures you'll see across common rivet nut specifications. Note that these are representative values based on installation into 2–3 mm steel sheet — actual figures vary by manufacturer, base material, and installation quality.

These figures represent the capacity of a single rivet nut installed into steel sheet of adequate thickness. Shear strength values typically run 60–80% of the pull-out figures for the same fastener. For safety-critical applications, always apply a safety factor of at least 3:1 to 4:1, meaning you should not load a fastener rated at 1,200 lbs to more than 300–400 lbs in service. Always refer to the specific manufacturer's data sheet for the exact product you're using, as construction quality and heat treatment vary between brands.

How Base Material Thickness Changes Everything

The load ratings above assume installation into steel sheet of adequate thickness for the rivet nut size. In reality, the thickness and strength of the base material you're installing into has an enormous effect on how much weight a rivet nut can actually hold — often more so than the rivet nut itself. A high-strength stainless steel rivet nut installed in thin aluminum sheet is only as strong as the aluminum allows it to be.

Minimum Sheet Thickness Requirements

Every rivet nut has a specified grip range — the minimum and maximum sheet thickness it is designed to clamp. If the base material is thinner than the minimum grip range, the rivet nut will not form a proper bulge on the blind side, resulting in a loose, understrength installation that can pull out at a small fraction of its rated capacity. As a general rule, for M6 rivet nuts, you want at least 1.5 mm of steel or 2.0 mm of aluminum. For M8 and larger, 2.0–3.0 mm of steel is the practical minimum for full-strength installation. Using a rivet nut in material thinner than specified is one of the most common causes of early fastener failure in DIY and light fabrication work.

Base Material Strength Matters as Much as Thickness

A rivet nut installed in mild steel sheet will hold significantly more than the same fastener installed in the same thickness of aluminum or plastic. The blind-side flange of the rivet nut bears against the back face of the sheet material — if that material is soft or brittle, it will deform or crack around the fastener before the rivet nut itself reaches its rated pull-out strength. When installing into aluminum, reduce your load expectations by 40–60% compared to equivalent steel installation. For composite panels, fiberglass, or thin plastic sheeting, rivet nuts are generally not the correct fastener choice for any significant structural load — threaded plates or backing plates should be used instead.

Rivet Nut Body Style and Its Effect on Load Capacity

Not all rivet nuts have the same body geometry, and the body style directly affects both the pull-out strength and, critically, the torque-out resistance — how well the installed insert resists spinning when you tighten a bolt into it.

Round Body (Smooth Shank) Rivet Nuts

Standard round-body rivet nuts have a smooth cylindrical shank. They are the most common type and are straightforward to install. Their weakness is torque-out resistance — under high bolt tightening torque, a smooth round body can spin in the hole because there is no mechanical feature preventing rotation. This limits the safe bolt torque to relatively modest values and makes them less suitable for applications that require frequent bolt removal and reinstallation, where cumulative spinning can enlarge the hole over time.

Knurled Body Rivet Nuts

Knurled rivet nuts have a serrated or knurled outer surface on the shank. During installation, these serrations bite into the wall of the drilled hole and resist rotation far more effectively than a smooth body. Torque-out resistance on a knurled M8 rivet nut can be 3–5 times higher than the equivalent smooth-body design — often exceeding 30–50 Nm compared to 8–15 Nm for smooth body. For any application where you'll be regularly tightening and loosening bolts, or where high bolt preload is required, knurled body rivet nuts are the correct choice.

Hexagonal Body Rivet Nuts

Hex body rivet nuts require a hexagonal hole (punched or broached rather than drilled) but deliver the highest torque-out resistance of any rivet nut type. The flat sides of the hex body lock mechanically against the sides of the hex hole, effectively preventing any rotation regardless of the bolt torque applied. They are the preferred choice in automotive and aerospace fabrication where fastener integrity under vibration and repeated assembly cycles is critical. The requirement for a hex hole is the main limitation — it adds a step to hole preparation that is not feasible in all applications.

Installation Quality Has a Bigger Impact Than You Think

A rivet nut that has been correctly specified and is made from good-quality material can still fail well below its rated capacity if it is not installed properly. Poor installation is responsible for a significant proportion of rivet nut failures in the field, and most of these failures are entirely preventable.

• Incorrect hole size: The clearance hole for a rivet nut must match the manufacturer's specified hole diameter precisely. A hole that is too large prevents the rivet nut from gripping the sheet properly and allows the insert to rock or pull through at reduced load. A hole that is too small prevents the rivet nut from seating flush at the flange, which compromises the clamping geometry. Drill the hole to spec — do not rely on "close enough."
• Under-setting or over-setting: A rivet nut that has not been set to the correct stroke leaves an incomplete blind-side bulge that grips weakly. An over-set rivet nut has the blind-side flange collapsed so far that it cracks or the threaded section is distorted. Both conditions significantly reduce load capacity. Use a calibrated installation tool with a mandrel matched to the rivet nut specification — avoid impact drivers or improvised setting tools for structural installations.
• Misalignment: A rivet nut that is installed at an angle to the sheet surface will load unevenly under bolt tightening, concentrating stress on one side of the flange. This is a common failure mode in thin-wall tube applications where it is difficult to drill a perfectly perpendicular hole. Take time to ensure the hole is square to the surface before installation.
• Using the wrong tool: Hand-operated rivet nut tools are fine for small quantities of M4–M6 rivet nuts in thin material. For M8 and larger, or for materials harder than 2 mm steel, a pneumatic or cordless rivet nut tool delivers far more consistent setting force and significantly better installation quality. Inconsistent hand-tool pulling force is one of the primary causes of under-set rivet nuts in DIY applications.

Flat Head vs. Countersunk vs. Large Flange: Does Flange Style Affect Strength?

Rivet nuts are available with several flange profile options, and the choice does affect both the load distribution and the practical load capacity in certain applications.

Standard flat-flange rivet nuts are the default for most applications — the flange sits flush against the surface of the sheet and distributes the load over a defined contact area. Large-flange rivet nuts have a significantly wider flange diameter, which spreads the pull-out load over a larger area of the sheet surface. This is particularly valuable in thin or soft materials — the larger flange prevents the rivet nut from pulling through the material at the flange edge, effectively increasing the pull-out strength in those substrates by 20–40% compared to a standard flange. If you're installing into aluminum sheet thinner than 2 mm, or into composite panels, specifying a large-flange rivet nut is a straightforward way to improve the load rating without changing the thread size or switching materials.

Countersunk (CSK) flange rivet nuts are designed for applications where the surface must be completely flush — no protruding flange. The trade-off is reduced pull-out resistance at the flange interface, since the countersunk geometry concentrates load at the edge of the countersink rather than distributing it across a flat bearing face. CSK rivet nuts are best used where surface profile is the priority and loads are moderate — they are not the right choice for maximum load capacity.

Practical Load Examples: What Rivet Nuts Are Realistically Used For

Putting the numbers in context helps calibrate expectations. Here are common real-world use cases and the load demands involved:

• Body panels and trim on vehicles: Mounting plastic trim panels or thin sheet metal body sections typically involves pull-out loads of 50–200 lbs per fastener under normal conditions. M5 or M6 aluminum rivet nuts in 1.5–2 mm steel sheet handle this comfortably with large margins, which is why they are standard in automotive body assembly.
• Roof rack and cargo load points: A roof rack carrying 150 lbs of gear distributed across 4–6 mounting points imposes roughly 25–40 lbs of sustained pull-out load per fastener under static conditions — significantly more under dynamic road loads. M8 steel rivet nuts in 2 mm steel sheet with a 3:1 safety factor cover this application with room to spare, but the installation quality and base material must be verified rather than assumed.
• Equipment mounting in enclosures: Electronic control cabinets and equipment enclosures use rivet nuts to mount components and DIN rails to thin sheet metal walls. Typical loads are 20–100 lbs per fastener. M5 or M6 steel rivet nuts are standard here, and the main concern is torque-out resistance during assembly rather than ultimate pull-out strength.
• Structural brackets and load-bearing mounts: Rivet nuts are sometimes used to attach structural brackets — motor mounts, subframe brackets, or heavy equipment arms — in fabricated assemblies. These applications can involve sustained loads of 500–2,000 lbs per fastener. At these levels, M10 or M12 steel rivet nuts installed in adequate-thickness steel are capable of meeting the demand, but engineering calculations and testing are required. Rivet nuts should not be used as the sole fastening method for safety-critical structural connections without formal load verification.
• Aluminum extrusion frames: In modular aluminum framing systems for jigs, fixtures, and machine guards, rivet nuts are frequently installed in the thin walls of aluminum extrusions. Wall thickness in common extrusions is typically 1.5–3 mm. M6 large-flange aluminum rivet nuts work well here for loads up to 200–400 lbs, but M8 and larger in thin-wall aluminum extrusions require careful review of the base material capacity rather than simply relying on the rivet nut's rated strength.

Rivet Nuts vs. Weld Nuts vs. Clip Nuts: How Load Capacity Compares

Rivet nuts are not the only way to add a threaded connection to sheet metal — and understanding how they compare to alternatives helps with choosing the right fastening method for the load involved.

Rivet nuts occupy a practical middle ground — they deliver far more strength than clip nuts and are installable with no access to the blind side, making them the right tool for repairs, retrofits, and fabrications where drilling and setting from one side is the only option. Where both sides are accessible and loads are very high, weld nuts or self-clinching nuts will outperform rivet nuts. For most general-purpose sheet metal work, however, a properly installed steel rivet nut of the correct size is entirely adequate.

How to Find the Exact Load Rating for Your Specific Rivet Nut

Generic strength tables are useful for ballpark planning, but for any application where load matters — vehicle modifications, equipment mounting, structural brackets — you should work from the specific manufacturer's data for the exact product you are using. Here's how to do that reliably:

• Download the product data sheet: Major rivet nut manufacturers — including Avdel, Bollhoff, Gesipa, POP Fasteners, and Sherex — publish detailed technical data sheets for each product line. These include pull-out strength, shear strength, torque-out values, grip range, recommended hole sizes, and installation mandrel specifications. If a supplier cannot provide a data sheet for the product they are selling, source from a different supplier.
• Note the test conditions: Manufacturer load data is tested under specific conditions — base material type, thickness, and hole diameter. Confirm that your application conditions match the test conditions as closely as possible. If your material is thinner or softer than the test substrate, expect lower real-world performance than the published figure.
• Apply an appropriate safety factor: For non-critical applications, a 2:1 safety factor is a minimum. For dynamic loads (vibration, impact, cyclic loading), use 3:1 to 4:1. For safety-critical applications involving personnel safety, apply a minimum 4:1 factor and have the installation reviewed by a qualified engineer.
• Test in your actual material when possible: If you're installing dozens or hundreds of rivet nuts in a production or batch context, it is worth performing pull-out testing on samples installed in the actual base material under actual conditions. A simple bench pull-out test with a load cell will quickly confirm whether your installation is achieving the expected strength — and catch any tooling or process issues before they become field failures.