Weld Nuts
What Are Weld Nuts?
Weld nuts are specialty nuts designed to be permanently welded to a base material, creating strong, captive threads where tapping is impractical or too thin. Common styles include projection (hex) weld nuts, retainer (floating cage) weld nuts, and round-base spot weld T-nuts, each optimized for a specific welding process and alignment need.
Benefits of Weld Nuts
- Permanently captive threads on thin or hard-to-tap sections.
- High strength & repeatability for production assemblies.
- Faster assembly vs. loose nuts and back-side tools.
- Precise location with pilots, projections, or floating cages for misalignment forgiveness.
Common Applications for Weld Nuts
- Automotive body, chassis, and seat structures
- Appliances, enclosures, HVAC & sheet-metal fabrications
- Industrial equipment, racking, and fixtures
- Aerospace & transportation interiors (non-critical)
Types of Weld Nuts
Projection (Hex) Weld Nuts
Feature multiple raised projections and optional pilots. Projections localize heat for fast, consistent fusion during projection welding, while the pilot helps with positioning and threads protection. Ideal for high-torque joints and high-volume production.
Retainer (Floating Cage) Weld Nuts
A nut held in a welded cage “floats” slightly, allowing fastener engagement even when mating holes are misaligned. Great for blind assemblies and when stack-up tolerances are difficult to control.
Round-Base Spot Weld T-Nuts
A circular base with a centered threaded barrel (T-shape) designed for spot welding and through-the-hole applications. The round flange spreads load and resists pull-through while keeping a low profile.
Materials & Finishes
- Low Carbon Steel: Most common for reliable welding; may be supplied plain or with light protective films that are weld-friendly.
- Stainless Steel (e.g., 304/18-8): For corrosion resistance; requires appropriate welding setup and practices.
How Weld Nuts Are Installed
- Projection Welding: Current and pressure collapse the nut’s projections to create the weld; ideal for hex projection nuts and thicker sheet.
- Spot Welding: Electrodes clamp and weld through the nut’s base flange; commonly used with round-base T-nuts.
Good practice: Clean, consistent faying surfaces; correct electrode geometry; proper squeeze, weld time, and current; and fixturing that supports accurate location.
How to Choose the Right Weld Nut
- Base metal & thickness: Match nut style and weld process to your sheet thickness and material.
- Alignment needs: Use pilots or floating cage nuts for misalignment tolerance.
- Load & torque: Projection hex nuts handle higher torque; round-base T-nuts spread load on thin sheet.
- Thread size & protection: Pick thread (UNC/UNF or metric) and plan for post-weld finishing/coatings if required.
Weld Nuts FAQ
To add durable, captive threads to sheet metal or structures that are too thin or impractical to tap, enabling fast, repeatable assembly from one side.
Projection welding uses raised points on the nut that concentrate heat for a rapid, consistent weld—common with hex projection nuts. Spot welding uses flat electrodes to weld the nut’s flange (e.g., round-base T-nuts) directly to the sheet.
Retainer (floating cage) weld nuts. The nut can float inside its cage to accommodate off-center or tolerance-stacked holes.
Yes. Stainless weld nuts are available, but welding parameters and technique must suit stainless to ensure a sound weld and corrosion resistance.
Use nuts with pilots where available, proper fixturing, and keep spatter away from the threads. Clean surfaces and correct parameters help prevent contamination.
Common UNC/UNF and metric sizes (e.g., #10, 1/4-20, 5/16-18, M5, M6, M8, etc.). Select to match your mating fasteners and load requirements.
Yes, often, especially on carbon steel. After welding, assemblies may be plated or painted. Ensure the the chosen finish is compatible with the application.