How to Use a Rivet Nut Tool: Choosing M3–M8 Sizes and Installing Rivnuts
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A rivet nut (also called a rivnut or blind threaded insert) gives you a strong threaded hole in material that is too thin to tap, such as sheet metal, aluminium panels, tubing or plastic. You install it from one side, so it works where you cannot reach the back of the panel: car body work, trailer frames, roof racks, cabinets and DIY brackets.
How a rivet nut works
The rivet nut is a short tube with an internal thread and a flange on one end. You thread it onto a mandrel, push it into a drilled hole and pull the mandrel back. The thin section of the tube collapses behind the panel and forms a bulge that clamps the material. After you unscrew the mandrel, you are left with a permanent thread for a bolt.
Choosing the size: M3 to M8
- M3 and M4 – light brackets, trim, electronics enclosures and thin aluminium.
- M5 and M6 – the most common sizes for general automotive and DIY work, such as license plate mounts, panels and accessories.
- M8 – heavier brackets, racks and frame mounting where you need a larger bolt.
Always check the drill size listed for each rivet nut size. The hole must match the outside diameter of the rivet nut body. A hole that is too big lets the nut spin; a hole that is too small stops it from seating flush.
Step by step
- Mark and drill the hole at the recommended size. Deburr both sides so the flange sits flat.
- Thread the rivet nut onto the mandrel until the end of the mandrel is just flush with, or slightly past, the end of the nut.
- Insert it into the hole and keep the tool square to the panel.
- Set it by turning or squeezing the tool until you feel firm resistance. Do not keep forcing it after that point, or you can strip the thread.
- Unscrew the mandrel and test-fit your bolt.
Common problems
The nut spins in the hole: the hole is oversized or the nut was not fully set. Use a slightly smaller hole for the next one, or try a knurled or hex-body rivet nut.
The thread is damaged: the mandrel was not threaded in far enough, or too much force was used. Make sure the mandrel engages the full thread before setting.
What you need
Our rivet nut mandrels and nuts kit covers M3 to M8, so you can match the size to each job. For accurate holes, a step drill bit set is handy on thin sheet metal. Browse more in Utility Tools.
Always wear eye protection when drilling metal, and check the product page for exact sizes and what is included in each kit.