Rivet Nut Selection Guide: Types, Sizes, Materials and Sheet-Metal Strength Matching
Executive Summary
On thin sheets, aluminum profiles, magnesium die castings and engineering plastics, direct tapping strips after a few times, welding a nut warps the part, and a press-in nut needs back-side access. The blind rivet nut builds a permanent, high-strength internal thread on thin sheet in one blind-side plastic forming step. Selection must answer four questions at once: which head and body style, what size, what material, and whether it matches this sheet. Against the GB/T 17880 series and the Bollhoff RIVNUT system, this article clears up the most common selection pitfalls.
Table of Contents
- What to Look at First: Installation Method Decides Everything
- Choosing the Type: Head Style, Body Style and Blind-Hole Structure
- Size and Strength: Thread Size vs Load Matching
- Choosing Material: Steel, Stainless, Aluminum and Galvanic Corrosion
- Sheet Applicability: Thickness, Hole Diameter and Clamping Range
- A Selection Decision Table and Common Pitfalls
What to Look at First: Installation Method Decides Everything
The core value of a blind rivet nut is single-sided blind installation: approach the base plate from one side only; a dedicated rivet tool pulls the nut's internally threaded zone, so the unthreaded thin-wall bulge zone experiences axial compressive stress past yield, buckles axially and folds outward, forming a closed bulb on the back of the base plate and clamping the plate between head and bulb. The whole process usually finishes within 3 seconds; it is a cold press-join with no weld heat-affected zone (HAZ), no warping of thin sheets, and no damage to pre-coated surfaces.
That is why blind rivet nuts are especially suited to: closed profiles (auto body tubes, drone arm square tubes), blind spots in server chassis, closed battery-pack cavities, and any thin sheet whose back side is unreachable. The first selection step is not picking a size, but confirming whether this connection point needs "through-hole or blind-hole", "sealing or not", and "how high the anti-twist requirement"—these three directly decide the type.
Choosing the Type: Head Style, Body Style and Blind-Hole Structure
The rivet-nut type combines three dimensions: head style (the head's relation to the sheet face), body style (outer-wall shape, deciding the anti-rotation method), and hole style (open end vs closed end). The domestic GB/T 17880 series divides by head style: GB/T 17880.1 flat head, 17880.2 countersunk head, 17880.3 small countersunk, 17880.4 small flat head, 17880.5 120° small countersunk rivet nut.
| Body Style | Geometry | Anti-Twist / Pull Mechanism | Typical Use |
|---|---|---|---|
| Flat head knurled | Longitudinal knurl on outer wall | Knurl bites into parent hole wall during bulging; friction raises anti-twist | Consumer-electronics housings, sheet-metal chassis, appliances |
| Semi-hex / full hex | Hex outer wall | Mated with a hex punched hole; upgrades from "friction anti-rotation" to "geometric mechanical lock" | NEV electric-control housings, body structural parts |
| Internal-external hex | Both internal and external hex | External rigid geometric anti-rotation + high-torque internal fastening; high load capacity | Heavy structures, aerospace, heavy equipment |
| Closed end (blind) | Tail sealed | Cuts gas/liquid leak path; with seal ring reaches IP67/IP68 | Outdoor energy-storage cabinets, liquid-cooled servers, battery packs |
The Bollhoff RIVNUT system also derives special models by performance: HRT (High Resistance Thread, wear-resistant thread for repeated assembly), SFC (Smart for Composite, for composite/sandwich panels), PN (Ultimate Pull-out, ultra-high pull-out), and sealing series with a Seal Ring.
Size and Strength: Thread Size vs Load Matching
The rivet-nut size is set by thread nominal diameter × pitch; common metric coarse covers M3–M12 (e.g. M6×1.0, M8×1.25, M10×1.5), with fine threads also available. When selecting, separately check "nut-body strength" and "its anchoring strength on the sheet":
- Nut-body strength: the internal thread must withstand the later bolt's tightening and working load; steel rivet-nut bodies are controlled to the property classes corresponding to GB/T 3098.1/3098.2, ensuring the thread does not strip or burst under tightening.
- Anchoring strength: the rivet nut's pull-out and anti-twist force on the sheet, jointly decided by sheet thickness, hole diameter, body style and bulb-forming quality—not by the nut's internal thread.
Design should reverse-calculate from working load: first compute the required clamp force, choose the corresponding thread size, then confirm that this size's pull-out/twist values at the target sheet thickness cover the service. Suppliers such as Bollhoff give pull-out and anti-twist reference values by "thread size × sheet-thickness range"; when selecting you must look up the corresponding thickness band, not just the thread size.
Choosing Material: Steel, Stainless, Aluminum and Galvanic Corrosion
Choosing the wrong material is the most hidden and fatal pitfall for rivet nuts in lightweighting projects. When a steel rivet nut is fitted into an aluminum-alloy or magnesium-alloy base plate, two risks trigger:
- Base bursting / crushing: aluminum and magnesium have lower ductility than mild steel; if the bulb's radial expansion force is too large, or the punched hole is rough with micro-cracks, the stress concentration around the hole splits the light alloy. You must fine-tune the pull stroke and pull force, and control the rivet-nut material hardness gradient.
- Galvanic corrosion: steel electrode potential is clearly higher than aluminum (~-0.76 V) and magnesium (~-2.37 V). A carbon-steel rivet nut in direct contact with Al/Mg in damp, salt-spray conditions forms a micro-cell, and the light metal as anode is accelerated in corrosion, loosening or even peeling the fastener.
| Material | Suitable Base Plate | Corrosion / Temp Traits | Typical Scenario |
|---|---|---|---|
| Carbon steel (zinc / zinc-nickel) | Steel, thick plate, general industry | High strength, low cost; needs coating for corrosion | Sheet-metal chassis, steel structures, general assembly |
| 304 stainless | Aluminum alloy, stainless | Stable potential; small potential gap with aluminum; suppresses galvanic corrosion | NEVs, outdoor, light-alloy housings |
| Aluminum-alloy rivet nut | Aluminum alloy, light alloys | Potential matched; light weight | Drones, eVTOL, weight-saving structures |
Sheet Applicability: Thickness, Hole Diameter and Clamping Range
Each rivet-nut size has an applicable sheet-thickness range (clamping range), set by the bulge-zone length: too thin and the bulb does not fold fully, giving insufficient anchoring; too thick and head and bulb cannot clamp, or the rivet is not pulled into place. When selecting, pick the nut length band by "which clamping band the sheet thickness falls into" rather than using one size universally.
Hole diameter is equally critical: too large and the rivet nut wobbles in the hole with an eccentric bulb; too small and the bulge zone cannot squeeze in, scratching the coating. Proper selection tables give the recommended drill diameter and tolerance for each size (generally mm-class fit). For hex body styles, the base plate must be punched with a hex hole rather than a round hole, otherwise the hex outer wall provides no geometric lock.
| Design Element | Selection Rule | Wrong Consequence |
|---|---|---|
| Thickness / clamping range | Pick the length band by actual sheet thickness | Thin sheet = weak anchoring; thick sheet = cannot clamp |
| Drill diameter | Machine per the recommended hole diameter + tolerance | Oversize = wobble/eccentric; undersize = scratched coating |
| Hex punched hole | Hex body must be paired with a hex hole | Hex outer wall fails; falls back to friction anti-rotation |
| Surface state | Light alloy + steel part needs an isolating coating | Galvanic corrosion; premature joint failure |
A Selection Decision Table and Common Pitfalls
- Ordinary sheet metal / chassis, cover, static load, two-sided access: flat-head knurled carbon-steel rivet nut; size by the bolt.
- Closed profile / blind spot, back side unreachable: must install blind; pick a rivet nut in the corresponding clamping range.
- Repeated assembly, sustained vibration: semi-hex/full hex, or choose the HRT wear-resistant thread type.
- Need sealing and waterproofing: closed end + Seal Ring, targeting IP67/IP68.
- Aluminum/magnesium light-alloy base: 304 stainless or aluminum-alloy rivet nut, with an isolating coating at the contact face.
- Composite / sandwich panel: choose the SFC special type to avoid collapsing the sandwich.
Rivet-nut selection is not "picking one nut" but "choosing a thread-joining system": first set the type by blind-install/seal/anti-twist, then set size by load, set material by the base plate, and set the clamping band by sheet thickness and hole diameter. Get these four right, and the internal thread on thin sheet is both firm, durable and corrosion-free.
Conclusion: Four Steps to Correct Rivet-Nut Selection
Domestic rivet nuts have full national-standard support: GB/T 17880.1 flat head, 17880.2 countersunk, 17880.3 small countersunk, 17880.4 small flat head, 17880.5 120° small countersunk rivet nut; body strength is checked against GB/T 3098.1/3098.2, and corrosion verification per the GB/T salt-spray test. Selection follows four steps of "type → size → material → thickness/hole": type decides blind install and anti-rotation, size decides body and anchoring strength, material decides galvanic-corrosion risk, and thickness/hole decides anchoring reliability.
YF Zhichengjia, founded in Shenzhen in 2005, is a fastener manufacturer; rivet nuts are one of its core product lines, and it can provide selection and customization across carbon-steel/304-stainless/aluminum-alloy materials, flat/countersunk head, knurled/hex/closed-end series and sealing types. For more material, see the technical documentation library, or contact our technical engineers for a one-on-one selection evaluation.
