Recent from talks
Nothing was collected or created yet.
Rivet nut
View on Wikipedia


A rivet nut, also known as a blind rivet nut, or rivnut,[1] is a one-piece internally threaded and counterbored tubular rivet that can be anchored entirely from one side. It is a kind of threaded insert. There are two types: one is designed to form a bulge on the back side of the panel as a screw is tightened in its threads. The other is similarly drawn in using a screw, but is drawn into the sleeve instead of creating a bulge.[2][3]
History
[edit]The first rivet nut was created by BF Goodrich in the 1930s, and sold under the trademark RIVNUT®. It was first used to mount rubber de-icing boots to aircraft wings.[4]
Usage
[edit]In the field of aviation, rivet nuts are often used to attach various items, such as static dischargers and inspection access covers, to the surface of an aircraft.[citation needed] Rivet nuts are an ideal replacement for weld nuts because they will not distort base materials, eliminate weld splatter, toxic fumes, and other by-products of the welding process, and can be installed in many different kinds of material including steel, plastic, composites, and fiberglass. [5]
See also
[edit]References
[edit]Notes
[edit]Bibliography
[edit]- RIVNUT® The Original Blind Rivet Nut (PDF), Böllhoff Inc., 2010, retrieved 2018-09-25
- McMaster-Carr catalog (114th ed.), McMaster-Carr.
- Smith, Carroll (1990), Carroll Smith's Nuts, Bolts, Fasteners, and Plumbing Handbook, MotorBooks/MBI Publishing Company, ISBN 0-87938-406-9.
Rivet nut
View on GrokipediaOverview
Definition and Function
A rivet nut, also known as a blind rivet nut or nutsert, is a one-piece, internally threaded, tubular fastener designed to be inserted into a pre-drilled hole in a workpiece and anchored entirely from one side without access to the opposite side.[4] It features a hollow body with internal threading and a counterbored head, allowing it to function as a blind insert that deforms to secure itself in place.[1] The primary function of a rivet nut is to create a strong, reusable threaded hole in materials that are too thin, soft, or brittle for traditional tapping or nut installation, enabling secure attachment of bolts or screws where conventional methods would cause distortion or failure.[5] This makes it particularly valuable for applications requiring reliable fastening in limited-access scenarios, such as joining panels or components without backing support.[6] Key characteristics include its blind installation process, which relies on deformation—typically the formation of a bulging or closing head on the inaccessible side—to grip the material and provide high pull-out strength.[7] Rivet nuts are versatile for use with a range of materials, including metals, plastics, composites, and fiberglass, accommodating diverse industries like automotive, aerospace, and appliances.[4] Originally developed in the 1930s, the rivet nut was branded as "RIVNUT®" by BF Goodrich for its initial applications in aircraft assembly.[4]Basic Operation
The basic operation of a rivet nut involves inserting the fastener into a pre-drilled hole in the workpiece and then deforming it using a specialized tool that applies axial pull force via a threaded mandrel. This deformation secures the rivet nut in place, creating a strong threaded anchor point accessible from one side.[8] Rivet nuts employ two primary deformation mechanisms to achieve fixation. In the first, compression forms a bulge at the blind end of the rivet nut, where the tubular body collapses inward and expands outward against the far side of the workpiece, creating a mechanical interlock.[1] The second mechanism involves drawing the sleeve portion of the rivet nut into a countersunk or swaged shape at the accessible end, which clamps the material tightly and distributes compressive forces across the hole's perimeter.[1] These processes rely on the plasticity of common materials such as aluminum or steel, allowing controlled deformation without cracking.[8] Once installed, load distribution occurs as the internal threads of the rivet nut engage with a mating bolt, transferring both torque and axial forces through the deformed body to the workpiece. The bulged or swaged sections act as anchors, converting rotational and pulling loads into radial and axial compression against the surrounding material.[8] This engagement ensures even stress distribution, with the deformed geometry enhancing resistance to shear and tension. The physics of securing relies on radial and axial expansion of the rivet nut, which generates high frictional forces and a mechanical interlock to prevent pull-out or rotation under load. The bulge or swage creates a wedging effect that embeds the fastener into the workpiece, while the threaded interface provides precise torque transmission without slippage.[1] This dual-action mechanism achieves pull-out strengths typically exceeding 2.4 kN and torque-to-turn values up to 15 Nm for standard sizes, depending on material thickness and type.[8] Installation torque guidelines vary by rivet nut size and material but follow general ranges to ensure proper deformation without over-stressing the fastener. For example, M6 rivet nuts are typically set at 10-15 Nm, with aluminum bodies requiring around 9.5-12 Nm and steel bodies up to 15 Nm to achieve optimal clamping.[8][9] Exceeding these values risks thread damage or incomplete setting, while under-torquing may result in insufficient grip.[8]History
Invention
The rivet nut, commonly known under the trademark Rivnut®, was invented in 1936 by the B.F. Goodrich Company to provide a reliable blind fastening solution for aviation applications. It addressed the critical need for securing components to thin materials like aluminum sheets without requiring access to both sides of the workpiece.[4][10] The primary purpose of this invention was to attach rubber de-icing boots to the leading edges of aircraft wings, where traditional methods such as welding or soldering proved impractical due to limited access and the risk of damaging delicate structures. The design allowed installation from one side only, forming a strong threaded anchor that could withstand vibrational stresses in flight. This innovation was particularly vital for military aircraft during World War II, enabling efficient assembly in constrained environments.[4][11] The foundational patent for the rivet nut is U.S. Patent No. 2,149,199, titled "Tubular rivet," filed on August 13, 1936, by inventor Harry E. Waner and assigned to the B.F. Goodrich Company. Granted on February 28, 1939, the patent describes a one-piece tubular device with internal threads, a flanged head, and a deformable body that expands radially upon axial compression to create a secondary flange, thereby locking securely into the parent material. This mechanism overcame prior limitations in blind fasteners by providing high torque resistance and reusability for threaded connections.[12]Development and Adoption
Following the initial invention for aviation applications in 1936, rivet nut technology expanded significantly in the post-World War II period as demand grew for reliable blind fasteners in diverse manufacturing sectors. B.F. Goodrich, the original developer, licensed the RIVNUT® trademarked design to the AVK Corporation, enabling the first commercialization and scaling of production beyond military uses.[11] This licensing facilitated mass production in the 1950s, with AVK focusing on efficient manufacturing processes to meet rising industrial needs. Key milestones included widespread adoption in the automotive industry, where rivet nuts were employed for assembling body panels and attaching thin metal skins to frames, offering advantages in accessibility and strength over traditional nuts and bolts.[11] By the 1970s, standardization efforts advanced through organizations like the International Organization for Standardization (ISO) and the American Society of Mechanical Engineers (ASME). These standards ensured interoperability and quality consistency, accelerating integration into global supply chains. In the 1980s, modern developments introduced high-strength variants optimized for composite materials, addressing challenges in lightweight construction for aerospace and automotive applications. The global market experienced robust growth thereafter, with annual production surpassing millions of units by the 2000s to support expanding uses in electronics, appliances, and construction.[13] Influential companies have driven ongoing innovations, including Bollhoff, which acquired the RIVNUT® business in 2000 and expanded U.S. manufacturing; Stanley Engineered Fastening, known for Avdel-brand rivet nuts and pneumatic installation tools; and PEM (PennEngineering), a leader in engineered fasteners that complement rivet nut applications with high-performance variants.[14][15][16]Design and Components
Structure
A rivet nut consists of three primary components: the head, body, and tail. The head, which can be countersunk for flush mounting or flat/large flange for broader bearing surfaces, provides the installation interface and load distribution. The body is a tubular section containing internal threads for mating with bolts or screws, often featuring variations like round, hexagonal, or splined profiles. The tail, located at the opposite end, is the deformable portion that expands during setting to secure the fastener.[8][10][17] Standard dimensions for rivet nuts accommodate a range of applications, with thread sizes typically spanning M4 to M12 for metric standards or equivalent imperial sizes such as #8 to 1/2-13 UNC. Body lengths generally vary from 6 mm to 25 mm, depending on the required grip and material thickness. The grip range, which indicates the parent material thickness the fastener can secure, is commonly 0.5 mm to 6 mm, though specialized variants extend to 0.25 mm to 12.7 mm.[8][10][17] Engineering features enhance the rivet nut's performance and installation reliability. A counterbore or countersunk head allows for flush integration into the parent material, minimizing protrusions. Exterior knurling, splines, or hexagonal body shapes provide anti-rotation resistance by gripping the surrounding material. Internal threads adhere to established standards, such as ISO metric pitches or UNC/Unified coarse threads, ensuring compatibility with standard fasteners.[8][10][17] In cross-section, the pre-installation rivet nut appears as a straight, cylindrical tube with a threaded interior, uniform diameter from head to tail, and minimal deformation. Post-setting, the tail deforms outward to form a bulbous or multi-lobed bulge that clamps against the reverse side of the material, while the body may partially collapse to create a tight seal, transforming the overall shape into a secured, expanded profile.[8][10][17]Materials
Rivet nuts are primarily manufactured from steel, aluminum, and brass, each selected for specific performance characteristics. Low-carbon steel, such as grades 1008 or 1010, is commonly used for general-purpose applications due to its balance of strength and formability, while stainless steel variants provide enhanced corrosion resistance in harsh environments.[18] Aluminum, often in alloys such as 5056 (5000-series) or 6061 (6000-series), offers lightweight construction ideal for weight-sensitive uses, and brass, a copper-zinc alloy, is employed where electrical conductivity and tarnish resistance are required.[18][19][20][21] Key material properties include tensile strength, hardness, and compatibility with parent materials. Steel rivet nuts can achieve tensile strengths up to 800 MPa in Grade 5 variants, providing robust load-bearing capacity, with hardness typically in the 25-34 HRC range for durability.[19][22] Aluminum exhibits lower tensile strength but superior strength-to-weight ratio and inherent corrosion resistance, while brass offers moderate strength with high electrical conductivity. Compatibility considerations, such as using aluminum rivet nuts in aircraft assemblies to prevent galvanic corrosion with similar workpieces, ensure long-term integrity.[18][23] Coatings and finishes enhance performance against environmental degradation. Zinc plating on steel provides corrosion protection, with yellow or clear variants offering 50-100 hours to red rust and zinc-nickel exceeding 1,000 hours under ASTM B117 testing; passivation is applied to stainless steel for improved surface resistance. Polymer coatings, such as PVC or Raintite, are used on steel for added vibration damping and moisture barrier properties.[18][19][24] Material selection is guided by environmental factors, including temperature extremes from -55°C to 200°C for aluminum 6061-T6 and -55°C to 800°C for stainless steel 316L, as well as exposure to chemicals or humidity that demand high corrosion resistance. Stainless steel excels in chemical-laden settings due to its passivation layer, while aluminum suits non-corrosive, lightweight needs, and brass is chosen for conductive or decorative applications in mild conditions.[25][18][26]Types and Variants
Standard Rivet Nuts
Standard rivet nuts consist of a cylindrical body with uniform internal threads, providing a reliable blind fastening solution for attaching components to sheet metal or plastic where only one-sided access is available. The design features a counterbored tubular structure that deforms during installation to create a strong mechanical interlock with the parent material, accommodating standard bolt sizes for subsequent assembly. These fasteners are typically available in materials such as aluminum, steel, and stainless steel to suit various environmental and load conditions.[27] Common specifications include unified thread sizes from #6-32 to 3/8-16 UNC and metric threads from M5 to M10, with grip ranges varying by material thickness, often from 0.5 mm to 6 mm for standard applications. Load ratings for these rivet nuts generally provide shear strengths of 500-2000 N and pull-out (tensile) strengths of 1000-5000 N in typical steel configurations, ensuring sufficient performance for non-critical loads without requiring specialized tooling. For instance, a #10-32 steel rivet nut can achieve approximately 3330 N shear and 4830 N pull-out strength, depending on grip length and parent material.[27] Aerospace-grade versions adhere to standards such as NASM 1312-13 for double shear testing and NAS 1329/1330 for dimensional and material requirements, while general industrial types typically comply with quality systems like ISO 9001 and IATF 16949 for automotive applications.[27][28][29][30] These rivet nuts are particularly suited for low-to-medium torque applications, such as panel mounting in automotive assemblies, electronic enclosures, and furniture construction, where their round body design allows for straightforward installation in round holes and provides balanced load distribution without the need for high-precision alignment.[8]Specialized Types
Specialized types of rivet nuts are engineered variations designed to address specific challenges such as rotation resistance, environmental sealing, high structural loads, and installation in thin or composite materials. These adaptations modify the body shape, sealing mechanisms, or deformation patterns to enhance performance in demanding applications, while maintaining the core blind installation principle.[31][32] Hexagonal rivet nuts feature a multi-lobe, six-sided body that embeds into the parent material to prevent spin-out, particularly in soft or low-density substrates like aluminum or plastics. This design provides superior torque-to-turn resistance compared to standard round bodies, making them ideal for high-vibration environments. For instance, the High Strength Hexsert® from Stanley Engineered Fastening offers clamp forces equivalent to weld nuts, with thread proof loads matching tapped holes in soft metals. Similarly, Bollhoff's HEXNUT® installs into a pre-punched hexagonal hole for enhanced rotational stability.[33][34][35] Sealed or splash-proof rivet nuts incorporate O-rings, closed ends, or integrated seals to achieve watertight or IP-rated protection against moisture, oils, and contaminants, which is essential for automotive, marine, and outdoor applications. These variants prevent fluid ingress through the fastener, safeguarding underlying components from corrosion. Sherex's watertight rivet nuts, for example, provide robust sealing against water and viscous fluids in harsh environments. Bollhoff's RIVKLE® Seal Ring uses a captive O-ring for reliable waterproofing, while PEM's Deform-Nut® IP68 series features a plastic seal and closed barrel for full environmental protection in thin panels.[36][37][38] Heavy-duty rivet nuts are constructed with thicker walls and reinforced structures to withstand extreme pull-out and shear forces in structural assemblies, such as truck frames or heavy machinery. These variants prioritize load-bearing capacity, often achieving tensile strengths far exceeding standard types. Sherex's large-size full hex rivet nuts, for instance, demonstrate pull-out strengths over 30,000 pounds in testing, suitable for high-stress fastening. McMaster-Carr's heavy-duty hex models include large head flanges and thick collapse chambers for added strength in demanding scenarios.[39][35][40] Splined rivet nuts employ a ribbed or grooved body to improve grip and torque resistance in thin sheet materials, enabling secure installation in panels as low as 0.5 mm thick without hardness limitations. This design distributes stress evenly, reducing the risk of material deformation during torquing. Northern Precision's flat head splined body rivet nuts are available in steel and stainless steel for such thin applications. Rivets Online's ribbed K-series features a splined structure that enhances twist resistance over non-splined inserts in low-profile setups.[41][42] Peel-type rivet nuts facilitate rapid deformation for quick installation in composite materials, where the mandrel peels away segments of the body to create a broad bearing surface without cracking brittle substrates. This variant supports multi-material joining, including plastics and fiber-reinforced polymers. Bollhoff's RIVKLE® SFC series is specifically developed for such composites, offering peel-type deformation for reliable anchoring. Stanley Engineered Fastening's catalog includes peel-type options compatible with thin composites for vibration-resistant threads.[43][8]Installation Methods
Tools and Equipment
Manual rivet nut setters are essential for low-volume or field installations, featuring ergonomic designs with collet chucks that securely grip the rivet nut during setting. These hand tools typically accommodate thread sizes from M3 to M8, allowing users to install standard rivet nuts in materials up to several millimeters thick without requiring external power sources.[44][45] Power tools enhance efficiency for higher-volume production, including pneumatic setters that operate at 90-100 PSI to deliver consistent pulling force via compressed air.[46][47] Hydraulic and battery-powered variants provide precise torque control, with hydro-pneumatic models combining air drive and hydraulic amplification for reliable performance in demanding applications.[48][49] Accessories play a critical role in tool versatility, such as interchangeable nosepieces tailored to specific thread sizes like M5 to M12, ensuring proper alignment and fit during installation. Mandrels facilitate the pulling action to deform the rivet nut, while advanced models incorporate spin-out detection mechanisms to prevent incomplete settings and alert operators to errors.[50][51] Key specifications for these tools include stroke lengths of 5-10 mm to accommodate various material thicknesses, and pulling force outputs reaching up to 20 kN for robust deformation without damaging the fastener. Compatibility with established systems, such as those from Astro Pneumatic or Bollhoff, ensures seamless integration and adherence to industry standards for reliable rivet nut installation.[6][44][52]Step-by-Step Process
The installation of a rivet nut begins with proper preparation of the workpiece to ensure secure fastening. Drill a hole in the parent material to match the specified diameter for the rivet nut size, typically with a slight oversize for clearance, such as 0.01 mm larger than the nominal diameter for an M6 rivet nut (e.g., 9.01 mm hole for a 9.0 mm nominal).[8] Deburr the edges of the hole to remove any sharp burrs or debris that could interfere with insertion or setting.[10] The core installation procedure involves the following sequential steps using a dedicated rivet nut installation tool:- Thread the tool's mandrel into the internal threads of the rivet nut until secure.[8]
- Insert the rivet nut into the prepared hole from the access side of the workpiece, ensuring it sits flush against the surface.[53]
- Apply a controlled pull force using the tool to deform the tail of the rivet nut, expanding its body radially behind the material while the tool counters the head to form a clench.[10]
- Release the tool by reversing the mandrel and inspect the installation for a flush fit of the head against the surface and intact internal threads.[53]
