Rivet Nut Drill Bit Size Chart
This chart is a technical reference table used to match the correct drill bit size with a specific rivet nut (also known as a rivnut or blind nut). It plays a crucial role in ensuring that the rivet nut can be properly inserted and securely fastened into the pre-drilled hole without being too loose or too tight.
Metric Rivet Nut Drill Bit Size Chart
| Nut Size | Thread (Metric) | Body Diameter (mm) | Recommended Hole Size (mm) | Grip Range (mm) |
| M3 | M3 x 0.5 | 4.8 – 5.0 | 5.1 – 5.3 | 0.5 – 2.0 |
| M4 | M4 x 0.7 | 5.9 – 6.1 | 6.2 – 6.4 | 0.5 – 2.5 |
| M5 | M5 x 0.8 | 6.8 – 7.0 | 7.1 – 7.3 | 0.5 – 3.0 |
| M6 | M6 x 1.0 | 8.8 – 9.0 | 9.1 – 9.3 | 0.5 – 3.5 |
| M8 | M8 x 1.25 | 10.8 – 11.0 | 11.1 – 11.3 | 0.5 – 4.0 |
| M10 | M10 x 1.5 | 12.8 – 13.0 | 13.1 – 13.3 | 1.0 – 5.0 |
| M12 | M12 x 1.75 | 14.8 – 15.0 | 15.1 – 15.3 | 1.0 – 6.0 |
Inch Rivet Nut Drill Bit Size Chart
| Nut Size | Thread (Inch) | Body Diameter (inch) | Recommended Drill Size | Grip Range (inch) |
| #6-32 | 6-32 UNC | 0.255 – 0.260 | #F Drill (0.257”) | 0.020 – 0.080 |
| #8-32 | 8-32 UNC | 0.280 – 0.285 | #H Drill (0.266”) | 0.020 – 0.120 |
| #10-24 | 10-24 UNC | 0.312 – 0.318 | #I Drill (0.272”) | 0.020 – 0.120 |
| #10-32 | 10-32 UNF | 0.312 – 0.318 | #I Drill (0.272”) | 0.020 – 0.120 |
| 1/4”-20 | 1/4-20 UNC | 0.350 – 0.360 | 11/32” (0.344”) | 0.020 – 0.150 |
| 5/16”-18 | 5/16-18 UNC | 0.410 – 0.420 | 13/32” (0.406”) | 0.020 – 0.200 |
| 3/8”-16 | 3/8-16 UNC | 0.470 – 0.480 | 1/2” (0.500”) | 0.030 – 0.250 |
| 1/2”-13 | 1/2-13 UNC | 0.620 – 0.630 | 21/32” (0.656”) | 0.030 – 0.300 |
⚠️ Notes:
- The recommended hole diameter should be slightly larger than the rivet nut body, typically +0.1mm to +0.3mm, to allow easy insertion while preventing looseness.
- For hex or knurled rivet nuts, additional hole shaping is required, such as hex punching or anti-rotation slots.
- If using inch drill bits (e.g., #F, #I), consult a drill number-to-metric chart to ensure proper conversion and compatibility.
- It is highly recommended to measure hole size using gauges or calipers before installation to ensure compliance with the recommended range, improving success rate and reliability.
Why Is Choosing the Right Drill Bit Size Important?
Selecting the correct drill bit size is critical for the proper installation of rivet nuts, as it directly affects the strength, stability, and overall quality of the fastening. If the hole is too large or too small, it can lead to various issues that compromise the performance of the rivet nut.
Consequences of a Hole That Is Too Small:
- Rivet nut can’t be inserted: An undersized hole can prevent the rivet nut from being inserted smoothly. Forcing it in may damage the nut or deform the surface of the workpiece.
- Uneven deformation during setting: Excessive interference can lead to improper deformation of the rivet nut, resulting in reduced clamping force and poor locking performance.
- Risk of cracking: In hard materials or under high pulling force, the excessive stress can cause the rivet nut body to crack, reducing its service life.
Consequences of a Hole That Is Too Large:
- Rivet nut may spin or loosen: An oversized hole means poor contact between the nut and the hole wall, making it easier for the nut to rotate or fall out over time.
- Weak fastening: Without proper support, the rivet nut won’t clamp firmly, leading to a loose connection.
- Reduced pull-out strength: An overly large hole decreases the anchoring strength, which is especially problematic in applications involving vibration or tensile loads.
Summary and Recommendations:
- Always follow the recommended hole size: Each rivet nut size comes with a specific drill bit recommendation, which should be followed precisely.
- Allow proper clearance: It is generally advised to make the hole 0.1–0.3 mm larger than the rivet nut body diameter to allow easy insertion without sacrificing grip.
- Match hole shape for special nut types: Splined or hexagonal rivet nuts require anti-rotation holes (e.g., hex holes) instead of standard round holes.
Does Material Type Affect Drill Size Selection?
Yes, the type of material being drilled has a direct impact on drill size selection. Different materials possess unique physical properties such as hardness, elasticity, and thermal behavior, which can influence hole accuracy, edge quality, and the overall success of rivet nut installation. As a result, slight adjustments to the recommended drill size may be necessary based on the material.
a. Steel Sheet
- Material Properties: High hardness and stability; drilled holes are typically precise with minimal deformation.
- Drilling Suggestion: Standard recommended drill sizes are generally sufficient.
- Notes: Use high-speed steel (HSS) or carbide drill bits to minimize wear during drilling.
b. Aluminum Sheet
- Material Properties: Softer than steel; prone to thermal expansion during drilling, which may slightly enlarge the hole or deform edges.
- Drilling Suggestion: A drill bit slightly smaller (about 0.1mm less) than the standard size may compensate for thermal expansion.
- Notes: Drill at lower speeds and use lubricants to reduce burrs and heat buildup.
c. Plastic Sheet
- Material Properties: Very soft and flexible; drilling can cause stringing, melted edges, or shrinking around the hole.
- Drilling Suggestion: Use special drill bits designed for plastics, and allow for tighter hole tolerance control.
- Notes: Avoid high-speed drilling to prevent melting and hole distortion.
Summary:
- Although recommended drill sizes serve as a baseline, adjusting the bit based on material type can greatly improve installation quality.
- For critical or high-volume applications, always test on a sample before full-scale use.
- The softer the material, the more critical it is to maintain precise hole diameter and clean edge finishes to prevent rivet nut rotation or loosening.
Can All Rivet Nuts Use Round Holes?
Not all rivet nuts are suitable for round holes. Different rivet nut types have specific requirements for hole shapes, which are essential to ensure secure fastening and prevent loosening or rotation. Below is a detailed explanation of common rivet nut types and their corresponding hole shape requirements:
- Hole Requirement: Standard round hole.
- Application: General-purpose use; easy to install and suitable for most materials.
- Anti-Rotation Capability: Relies on clamping force and surface friction. However, in softer materials like plastic or aluminum, the anti-rotation effect is weaker.
- Hole Requirement: Standard round hole.
- Special Design: Features longitudinal ridges or splines on the outer surface.
- Advantages:
- Enhances grip against the hole wall;
- Improves anti-rotation performance in soft or coated materials;
- Less likely to rotate after installation compared to plain body nuts.
- Hole Requirement: Requires a properly sized hexagonal hole or a stamped hex hole.
- Main Advantage: Provides excellent anti-rotation performance, ideal for applications with vibrations or high torque loads.
- Note: Hex holes require precise machining, making them more suitable for mass production environments.
Summary:
- If anti-rotation requirements are minimal and the base material is hard, plain or splined rivet nuts with round holes are acceptable.
- For applications needing strong resistance to rotation or high-strength fastening, hex body rivet nuts with hexagonal holes are recommended.
- Ensuring the hole shape matches the rivet nut type is key to achieving firm installation and long-term reliability.
What Drill Bits Are Commonly Used?
When installing rivet nuts, selecting the correct drill bit size to precisely match the nut body diameter is essential to ensure a secure and reliable installation. Common drill bits fall into two main systems: Metric and Inch (Numbered/Lettered). Below are common types and their typical uses:
Metric Drill Bits
- Common sizes include:
- 6.0mm, 6.3mm, 6.9mm, 7.0mm, 7.3mm, 8.5mm, 9.1mm, 10.2mm, 12.1mm, etc.
- Applications:
- Suitable for most domestic and international standard metric-thread rivet nuts (e.g., M4, M5, M6, M8, M10).
- Advantages:
- High precision and intuitive units;
- Compatible with European and Asian threading standards;
- Widely supported by various industrial standards.
Inch Drill Bits
- Mainly three types:
- Numbered (e.g., #11, #7, #3)
- Lettered (e.g., F drill, H drill)
- Fractional (e.g., 1/4″, 5/16″, 3/8″)
- Common examples:
- #11 Drill (approx. 5.0mm diameter): often used for #10-24, M5 nuts;
- F Drill (approx. 6.51mm diameter): suitable for 1/4″-20 inch rivet nuts;
- 17/64″ Drill (approx. 6.75mm diameter): can be used for M6 nuts.
- Applications:
- Used mainly in North America or industries using inch-thread systems;
- For SAE threads or custom inch-thread fasteners.
Selection Tips:
- For metric rivet nuts, prioritize metric drill bits to avoid conversion errors;
- For inch rivet nuts (such as 1/4″-20), consult the rivet nut drill size chart to select the corresponding inch drill bit;
- If inch drill bits are unavailable, close-sized metric drill bits can be used with caution regarding tolerance;
- It is recommended to verify the drill bit diameter with a caliper before use to ensure it matches the recommended hole size.
What Tools Are Recommended for Drilling and Installation?
Choosing the right tools during the drilling and installation process of rivet nuts is crucial for ensuring quality and efficiency. Below are common and recommended tool types along with their functions:
1. Electric Drill
- Purpose: Used for drilling holes to prepare for rivet nut installation.
- Requirements: It is recommended to use a drill with adjustable speed and torque control to avoid over-drilling or damaging the material.
- Note: The hole size must meet the recommended dimensions to ensure the rivet nut fits smoothly without looseness.
2. Caliper
- Purpose: Used for precise measurement of the drilled hole diameter and the rivet nut body size.
- Importance: Ensures the hole diameter matches the rivet nut diameter to prevent installation failure caused by holes that are too large or too small.
3. Torque Control Tools
- Purpose: Controls the torque applied during installation to ensure the rivet nut is properly tightened.
- Advantages: Prevents overtightening that could damage the nut or undertightening that compromises joint strength.
- Application: Especially suitable for industrial mass production or applications requiring high joint strength.
4. Electric or Pneumatic Rivet Nut Tools
- Purpose: Specifically designed for fast and efficient rivet nut installation.
- Features: Labor-saving and high-speed installation, ideal for large-scale production.
- Advantages: Some advanced models come with adjustable torque settings for more precise and reliable installation.
- Limitations: Requires power or air supply, suitable for fixed work environments.
FAQs
1. If the drill hole is too large, what should I do?
If the hole is larger than the recommended size, the rivet nut may spin or fall out during installation or under load. Here are possible solutions:
- Use a larger-size rivet nut that fits the oversized hole.
- Switch to a rivet nut with anti-rotation features, such as a hex-body nut (if compatible with the hole shape).
- Apply adhesive (like epoxy) to improve holding strength, though this is not ideal for structural applications.
- Use a knurled or splined rivet nut that grips better in slightly oversized holes.
2. Can I use a metric drill bit for an inch-size rivet nut?
Yes, but with caution. You can use a metric drill bit that closely matches the recommended imperial size. For example:
- A #11 drill bit is approximately 7.0 mm.
- A 6.9 mm bit may work for a 17/64″ hole requirement.
Tips:
- Always check the manufacturer’s recommended hole size.
- Use a caliper to confirm the actual drill bit diameter.
- Perform a test fit before batch installation.
3. Are grip ranges flexible or fixed?
Grip ranges are fixed and specified for each rivet nut type and size. Installing a rivet nut outside of its rated grip range can lead to:
- Improper deformation during setting.
- Reduced pull-out or spin-out resistance.
- Failure under load or vibration.
Always check the grip range and choose a rivet nut that matches the thickness of the material being joined. For example:
- If your sheet is 1.5 mm thick, select a rivet nut with a grip range of 1.0–2.0 mm.
4. Can I reuse a rivet nut after removal?
Generally, rivet nuts are designed for one-time installation. Once they are deformed and expanded to grip the base material, they can’t return to their original shape. Reuse is not recommended because:
- The threads or body may be damaged during removal.
- Holding strength is significantly reduced if reused.
- Structural or safety-critical applications require new rivet nuts for reliable performance.
If frequent disassembly is needed, consider using threaded inserts or riveted studs instead.
5. What’s the difference between countersunk, flat head, and reduced head rivet nuts?
These head styles affect the appearance, installation method, and space requirement:
- Flat Head (Large Flange):
- Offers strong bearing surface.
- Ideal for soft or thin materials.
- Common in general applications.
- Countersunk Head:
- Sits flush with the surface after installation.
- Requires pre-drilled countersink.
- Best for applications where a smooth finish is needed.
- Reduced Head (Small Flange):
- Takes up less space on the surface.
- Suitable for tight or recessed mounting areas.
- May offer lower pull-through resistance.
