Choosing the right rivet nut hole size is one of the most important parts of a clean installation. If the hole is too small, the rivet nut may not seat correctly. If the hole is too large, the insert may spin, pull out, or fail to clamp the material properly.
This chart gives common starting points for rivet nut hole sizes, but you should always verify the exact part you are using. Rivet nuts vary by thread size, body style, flange type, knurling, grip range, and manufacturer.
Quick Rivet Nut Hole Size Chart
| Thread Size | Common Hole Size | Notes |
|---|---|---|
| M3 | Usually around 5 mm | Verify by part style |
| M4 | Usually around 6 mm | Common for small panels |
| M5 | Usually around 7 mm | Often used in light sheet metal |
| M6 | Usually around 9 mm | Common automotive and fabrication size |
| M8 | Usually around 11 mm | Some body styles require larger holes |
| M10 | Usually around 13 mm | Check grip range carefully |
| 8-32 | Varies by insert | Check supplier chart |
| 10-24 | Varies by insert | Common in light-duty installs |
| 10-32 | Varies by insert | Common in U.S. hardware |
| 1/4-20 | Varies by insert | Popular imperial alternative to M6 |
| 5/16-18 | Varies by insert | Similar use range to M8 |
| 3/8-16 | Varies by insert | Heavier-duty applications |
Important: Hole Size Depends on the Rivet Nut Style
A rivet nut is not sized only by its thread. Two M8 rivet nuts can require different hole sizes if one is round body and the other is hex body, half-hex, knurled, closed-end, or large-flange.
Common variables include:
- Round body vs hex body
- Smooth body vs knurled body
- Open-end vs closed-end
- Flat head vs countersunk head
- Standard flange vs large flange
- Steel, stainless steel, or aluminum
- Grip range and material thickness
Because of this, the chart should be used as a starting point, not a replacement for the manufacturer’s datasheet.
Metric Rivet Nut Hole Sizes
M4 Rivet Nut Hole Size
Many M4 rivet nuts use a hole around 6 mm, but the exact size depends on the insert body. M4 is common for small brackets, access panels, light sheet metal, electronics enclosures, and small fabricated parts.
M5 Rivet Nut Hole Size
Many M5 rivet nuts use a hole around 7 mm. Some suppliers list slightly different values, such as 7.0 mm or 7.1 mm, depending on the rivet nut design. M5 is a useful size for light-to-medium sheet metal, small brackets, panels, and interior mounting points.
M6 Rivet Nut Hole Size
Many standard M6 rivet nuts use a hole around 9 mm. This is one of the most common sizes for automotive, van builds, brackets, racks, equipment panels, and general fabrication.
M8 Rivet Nut Hole Size
Many M8 rivet nuts use a hole around 11 mm, but some M8 body styles require larger holes. This is especially important when comparing round body, hex body, and large-flange inserts. Always check the exact part before drilling.
M10 Rivet Nut Hole Size
Many M10 rivet nuts use a hole around 13 mm, but this can vary. Since M10 inserts are often used for heavier loads, it is especially important to match the hole size, grip range, and parent material thickness.
Imperial Rivet Nut Hole Sizes
Imperial rivet nuts are common in the United States and are often used in automotive work, off-road builds, equipment repair, trailers, brackets, and general fabrication.
Common imperial sizes include:
- 8-32
- 10-24
- 10-32
- 1/4-20
- 5/16-18
- 3/8-16
Imperial rivet nut hole sizes should be checked against the supplier’s drill chart. Do not assume that the closest metric size uses the same hole.
Why Rivet Nut Hole Size Charts Disagree
Rivet nut charts often disagree because they are not always describing the same part.
For example, one chart may show a standard round-body steel insert. Another may show a full-hex insert. Another may show a large-flange or closed-end version. Even if the thread size is the same, the outside body diameter can be different.
This is why you may see different recommended holes for the same thread size.
The safest approach is:
- Identify the exact thread size.
- Identify the exact rivet nut body style.
- Check the grip range.
- Check the manufacturer’s hole size.
- Test the insert in scrap material before drilling the final panel.
What Happens If the Hole Is Too Small?
If the hole is too small, the rivet nut may not insert cleanly. You may damage the knurling, scrape the coating, deform the panel, or force the insert into the hole at an angle.
A tight fit can be good, but the insert still needs to seat flat against the panel.
What Happens If the Hole Is Too Large?
If the hole is too large, the rivet nut may not grip the panel properly. Common symptoms include:
- The rivet nut spins during installation
- The bolt spins the insert later
- The insert pulls out under load
- The flange does not sit square
- The installed thread feels loose or weak
An oversized hole is one of the most common causes of failed rivet nut installations.
Grip Range Matters Too
Hole size is only one part of the installation. Grip range is just as important.
Grip range is the material thickness range that the rivet nut is designed to collapse against. If the material is too thin or too thick for the insert, the rivet nut may not set correctly even if the hole size is right.
Before installing, check:
- Hole size
- Material thickness
- Grip range
- Rivet nut material
- Tool stroke or setting force
- Bolt size and thread pitch
Best Practice: Test Before Final Installation
Before drilling the final part, test the rivet nut in scrap material with the same thickness. Drill the recommended hole size, set the rivet nut, and check whether it seats flat, collapses properly, and resists spinning.
This is especially important for automotive panels, thin sheet metal, aluminum, stainless steel, painted parts, and expensive finished panels.
Related Guides
- M5 Rivet Nut Hole Size Guide
- M6 Rivet Nut Hole Size Guide
- M8 Rivet Nut Hole Size Guide
- Rivet Nut Grip Range Explained
- Why Rivet Nuts Spin and How to Fix Them
- Rivet Nut Hole Too Big: What to Do
FAQ
What size hole do I drill for a rivet nut?
It depends on the rivet nut thread size, body style, and manufacturer. Many metric rivet nuts follow common hole sizes such as around 7 mm for M5, 9 mm for M6, and 11 mm for M8, but you should always verify the exact part.
Should a rivet nut fit tight in the hole?
The rivet nut should fit cleanly without excessive force. It should not rattle loosely in the hole, but it also should not need to be hammered in unless the manufacturer specifically allows that fit.
Can I use a step drill for rivet nuts?
Yes, a step drill can work well if it produces a clean, round hole at the correct size. Be careful not to oversize the hole.
Why does my rivet nut spin?
A rivet nut can spin because the hole is too large, the grip range is wrong, the material is too thin, the insert was under-set, or the wrong body style was used for the application.
Do steel and aluminum rivet nuts use the same hole size?
Sometimes they do, but not always. Hole size depends more on the exact insert design than the material alone. Always check the supplier’s dimensions.