Description
Pre-Bulbed Rivet Nut Sizes, Grip Ranges & Specifications
The charts below list standard inch and metric pre-bulbed rivet nut sizes, part numbers, grip ranges, mounting hole sizes and dimensional specifications. Select the required thread size and material thickness to request a production quote.
THREAD SIZE(UNC) |
PART NO. |
Grip Range |
Hole Size |
Head Dia. / H |
Head Height / t |
Body Dia. / D |
Length / L |
| UNC 10-32 | TOPSN1032 | 0.020-0.175 | 0.312-0.317 | 0.5 | 0.038 | 0.31 | 0.8 |
| UNC 10-32 | TOPSN1032-L | 0.175-0.320 | 0.312-0.317 | 0.5 | 0.038 | 0.31 | 0.94 |
| UNC 1/4-20 | TOPSN420 | 0.020-0.280 | 0.386-0.391 | 0.625 | 0.058 | 0.384 | 1.03 |
| UNC 1/4-20 | TOPSN420-L | 0.280-0.500 | 0.386-0.391 | 0.625 | 0.058 | 0.384 | 1.26 |
| UNC 5/16-18 | TOPSN518 | 0.020-0.280 | 0.496-0.504 | 0.75 | 0.062 | 0.482 | 1.18 |
| UNC 5/16-18 | TOPSN518-L | 0.280-0.500 | 0.496-0.504 | 0.75 | 0.062 | 0.482 | 1.41 |
THREAD SIZE(Metric) |
PART NO. |
Grip Range |
Hole Size |
Head Dia. / H |
Head Height / t |
Body Dia. / D |
Length / L |
| M6PH1.0 | TOPSN6 | 0.50-7.10 | 9.80-9.93 | 15.9 | 1.5 | 9.76 | 26.2 |
| M6PH1.0 | TOPSN6-L | 7.10-12.70 | 9.80-9.93 | 15.9 | 1.5 | 9.76 | 32 |
| M8PH1.25 | TOPSN8 | 0.50-7.10 | 12.6-12.8 | 19 | 1.57 | 12.25 | 30 |
| M8PH1.25 | TOPSN8-L | 7.10-12.70 | 12.6-12.8 | 19 | 1.57 | 12.25 | 35.8 |
What Is a Pre-Bulbed Plus Nut?
A pre-bulbed plus nut is a type of blind rivet nut with a slotted body that expands into four load-bearing legs during installation. These legs form a wide footprint behind the parent material, helping distribute the load over a larger surface area.
The pre-formed bulb reduces the force required to set the fastener, making it suitable for thin sheet metal, plastics, fiberglass, composites and other materials that may be damaged by higher installation forces.
Also searched as pre-bulbed rivet nuts, cross nuts, slotted body rivet nuts, plus body inserts and blind threaded inserts, these fasteners create a strong, reusable internal thread when only one side of the application is accessible.
Available Thread Sizes
Standard sizes shown in the specification charts include:
Inch Thread Sizes
- #10-32 Pre-Bulbed Rivet Nut
- 1/4-20 UNC Pre-Bulbed Rivet Nut
- 5/16-18 UNC Pre-Bulbed Rivet Nut
Metric Thread Sizes
- M6 × 1.0 Pre-Bulbed Rivet Nut
- M8 × 1.25 Pre-Bulbed Rivet Nut
Each thread size is available in different grip ranges for varying material thicknesses. Additional inch and metric sizes may be manufactured for production requirements.
Refer to the specification charts above for exact mounting hole sizes, head diameters, body diameters and overall lengths.
Materials & Finishes
Pre-bulbed plus nuts are available in steel, with stainless steel, aluminum and brass available as custom options.
Available finishes may include:
- CR3 white zinc
- Yellow zinc
- Black zinc
- Zinc-nickel
- Nickel plating
- Application-specific finishes
Material and finish availability depends on thread size, performance requirements and production quantity.
Benefits of Pre-Bulbed Rivet Nuts
- Wide grip range accommodates varying material thicknesses
- Four expanding legs distribute the load over a broad backside area
- Strong resistance to pull-out in thin or soft materials
- Lower installation force than many standard rivet nuts
- Blind installation requires access from only one side
- Creates a strong, reusable internal thread
- Suitable for materials that cannot be tapped or welded
- Helps reduce the number of fastener sizes required in production
Pre-Bulbed Rivet Nut Installation
Pre-bulbed rivet nuts can be installed using compatible torque-controlled hand tools, pneumatic tools or production installation equipment.
The fastener is inserted into a properly sized mounting hole. As the mandrel pulls or applies controlled torque, the slotted body expands into four legs behind the material and clamps the fastener securely against the panel.
For reliable installation:
- Use the specified mounting hole size.
- Confirm that the material thickness is within the listed grip range.
- Use the correct mandrel and nosepiece.
- Keep the fastener perpendicular to the mounting surface.
- Set the installation stroke or torque for the selected part.
- Test the installation in the actual application material before production.
Do not assume that an oversized or irregular hole is acceptable. Correct hole size remains important for alignment and installation performance.
Typical Applications
Pre-bulbed plus nuts are commonly specified for industrial assemblies requiring blind installation, a wide grip range or additional backside load distribution.
Typical applications include:
- Automotive components
- Commercial trucks and trailers
- Transportation equipment
- Thin sheet metal assemblies
- Plastic and fiberglass components
- HVAC equipment
- Electrical cabinets and enclosures
- Appliances
- Agricultural equipment
- Machinery and industrial assemblies
- Panels with varying material thicknesses
Factory-Direct Supply & Custom Production
Imperial Rivets & Fasteners supplies factory-direct pre-bulbed rivet nuts and slotted body threaded inserts for OEMs, manufacturers, distributors and industrial assembly operations.
Standard inch and metric sizes are available in multiple grip ranges. We can also support production requirements involving custom thread sizes, materials, finishes and dimensional specifications.
Select a standard part from the specification chart above and add it to your RFQ. For custom requirements, provide the thread size, material thickness, mounting hole size, material, finish and estimated annual quantity.
Questions or Custom Requirements?
Contact our sales team at sales@imperialrivet.com or (630) 964-0208.
