Choosing the correct hole size is one of the most important parts of installing a rivet nut. Get it right and the insert sets firmly, holds torque, and stays put. Get it wrong and you end up with a spinning insert, a pulled-out fastener, or a set that looks fine until load is applied.
The hole must be large enough for the rivet nut body to slip in cleanly, but not so large that the insert has room to rotate or pull through. Even a few thousandths of an inch matters.
Important: Always confirm the final hole size with the manufacturer’s datasheet for the exact rivet nut you are using. Hole size can vary by thread size, body style, material, grip range, and manufacturer.
https://rivetnutguide.com/rivet-nut-size-calculator/Quick Rivet Nut Hole Size Chart
The tables below are designed to get you to the right number fast. If you know your thread size, you can find a common hole diameter and the closest standard drill bit in seconds. These are widely used reference sizes, not universal specifications. Your specific rivet nut brand, body style, and material may call for something slightly different, so treat these as a starting point rather than a final answer.
When in doubt, drill a test hole in scrap material first. A snug fit with no play is what you’re after before committing to your actual workpiece.
Metric Rivet Nut Hole Size Chart
| Thread Size | Common Hole Size Range | Closest Drill Size | Common Use |
|---|---|---|---|
| M3 | 4.9–5.0 mm | 5.0 mm | Light-duty panels, electronics, brackets |
| M4 | 5.9–6.0 mm | 6.0 mm | Enclosures, small brackets, light sheet metal |
| M5 | 6.9–7.1 mm | 7.0 mm | General sheet metal, equipment panels |
| M6 | 8.9–9.1 mm | 9.0 mm | Automotive, machinery, medium-duty mounts |
| M8 | 10.9–11.1 mm | 11.0 mm | Heavier brackets, frames, structural panels |
| M10 | 12.9–13.1 mm | 13.0 mm | Heavy-duty mounting, thick panels |
| M12 | 15.9–16.1 mm | 16.0 mm | Large assemblies, heavy-duty applications |
These values are common starting points. Some knurled, hex, closed-end, or large-flange rivet nuts may require different holes.
Imperial / SAE Rivet Nut Hole Size Chart
For SAE and imperial thread sizes, hole tolerances follow the same logic as metric, the body needs to slide in without play, but the fit should be snug enough that the insert can’t spin during or after setting. Fractional drill sizes don’t always land exactly on the ideal diameter, so the closest available size is listed alongside the decimal equivalent to help you verify you’re in the right range.
If you’re working with a letter or number drill index rather than fractional bits, cross-reference the decimal equivalent column against your drill chart to find the closest match.
| Thread Size | Common Hole Size Range | Closest Fractional Drill Size | Decimal Equivalent |
|---|---|---|---|
| #6-32 | 0.193–0.196 in | 13/64 in | 0.2031 in |
| #8-32 | 0.213–0.218 in | 7/32 in | 0.2188 in |
| #10-24 | 0.250–0.265 in | 17/64 in | 0.2656 in |
| 1/4-20 | 0.375–0.390 in | 25/64 in | 0.3906 in |
| 5/16-18 | 0.500–0.515 in | 33/64 in | 0.5156 in |
| 3/8-16 | 0.625–0.640 in | 41/64 in | 0.6406 in |
Fractional drill sizes may be slightly larger than the minimum body diameter. Always check the rivet nut manufacturer’s recommended hole diameter before drilling production parts.
What Is Rivet Nut Hole Size?
Rivet nut hole size refers to the diameter of the drilled or punched hole that accepts the rivet nut body before installation. It is not the thread size, it is the opening in the panel that the unset insert slides into.
The hole needs to match the outside body diameter of the rivet nut as closely as possible. During installation, the rivet nut body expands or collapses behind the panel to create a mechanical lock, and that process depends heavily on how well the insert fits the hole. Too loose and the insert has room to shift; too tight and it won’t go in cleanly. Beyond fit, hole size directly affects spin resistance, clamp strength, alignment, and pull-out performance, all of which determine whether the fastener holds up under real-world load. A correctly sized hole lets the rivet nut seat flush against the panel surface and set evenly, which is what gives the installation its holding strength.
Why Hole Size Matters
If the Hole Is Too Small
An undersized hole causes problems before the rivet nut even sets. The insert may not fit into the panel at all, or it may require force that scrapes or deforms the rivet nut body on the way in. If the insert doesn’t slide in squarely, the installation tool can’t set it evenly, leaving the rivet nut cocked at an angle or only partially collapsed. In coated or painted panels, forcing an oversized insert through a tight hole can chip or crack the finish around the opening. In worst cases, the insert never seats fully flush, which compromises both appearance and holding strength.
If the Hole Is Too Large
An oversized hole is often the more dangerous condition because the installation may look correct while the fastener is already compromised. With too much clearance, the rivet nut can spin freely in the hole during bolt installation, a frustrating problem that usually means the insert needs to be drilled out and replaced. Beyond spinning, a loose fit means the flange may not clamp tightly against the panel surface, reducing the clamping force the joint relies on. Under load, an oversized hole gives the insert room to shift, which can lead to pull-out failure when the bolt is tightened. If you’ve run into a situation where a rivet nut spins after setting, an oversized hole is one of the first things to check.
Metric Rivet Nut Drill Sizes
M3 Rivet Nut Hole Size
M3 rivet nuts are most common in light-duty applications where weight and space are at a premium, small enclosures, electronics housings, thin aluminum panels, and lightweight brackets. The typical hole size falls in the 4.9–5.0 mm range, with a 5.0 mm drill bit being the standard choice. Because the insert body is small, there is very little margin for error. A hole that is even slightly oversized relative to the body diameter can leave the insert with enough play to spin or pull out, so accurate drilling matters more here than at larger sizes. A drill press or center punch to prevent walking is worth the extra setup time.
M4 Rivet Nut Hole Size
M4 is a step up from M3 and shows up regularly in light sheet metal work, electronics assemblies, access covers, and small mounting brackets. The common hole size is 5.9–6.0 mm, and a standard 6.0 mm drill bit covers most applications. It’s a versatile size that handles a wide range of panel thicknesses and materials, and it’s popular enough that most rivet nut tool sets are sized to accommodate it without any adapter. If you work frequently with M4 inserts across different body styles and materials, a dedicated reference covering grip range, torque limits, and body options is worth having on hand.
M5 Rivet Nut Hole Size
M5 is the workhorse of the metric rivet nut range. It lands in a practical middle ground, strong enough for real structural use, small enough to fit panels where an M6 would feel oversized. You’ll find it used across general sheet metal fabrication, equipment panels, HVAC enclosures, and anywhere M4 doesn’t provide enough thread engagement but M6 would require a larger cutout than the design allows. The standard hole size is 6.9–7.1 mm, with a 7.0 mm drill covering most installations cleanly.
M6 Rivet Nut Hole Size
M6 is one of the most widely used rivet nut sizes across industries. It appears in automotive bodywork and trim, industrial equipment panels, server racks, machinery guards, and medium-duty mounting applications where a reliable threaded anchor is needed in thin material. The common hole size is 8.9–9.1 mm, drilled with a 9.0 mm bit. Because M6 is so broadly used, it’s also where body style choices, round smooth, round knurled, hex, make the most practical difference in spin resistance and pull-out strength. For a deeper look at hole sizing, torque values, and installation tips for this size, see our M6 Rivet Nut Hole Size and Torque Guide.
M8 Rivet Nut Hole Size
M8 rivet nuts move into higher load territory and are common in heavier brackets, structural panels, frames, and applications where the bolted joint will see real tension or vibration. The standard hole size is 10.9–11.1 mm, with an 11.0 mm drill being the typical choice. At this size, the choice of body style becomes especially important. A smooth round body in a slightly worn or oversized hole can spin under the torque required to tighten an M8 bolt, situations like this are where a knurled or hex body earns its place, biting into the parent material to resist rotation. Panel thickness also becomes a more critical variable at M8, since the insert needs adequate material behind the panel to set and clamp properly.
M10 and M12 Rivet Nut Hole Sizes
M10 and M12 rivet nuts are heavy-duty fasteners intended for substantial structural loads, thick panels, and applications where a welded nut or cage nut isn’t practical. M10 typically requires a 13.0 mm hole and M12 a 16.0 mm hole, openings large enough that the parent material needs to be strong enough not to deform or crack around the insert during or after setting. Thin or weak sheet metal is generally not suitable for these sizes without reinforcement. Installation tool requirements also increase significantly, most hand-operated rivet nut tools are not designed for M10 and M12, and attempting to set these sizes with an undersized tool can result in a partially set insert, a stripped mandrel, or tool damage. A pneumatic, hydraulic, or heavy-duty cordless tool is the right choice for production use at these sizes.
Imperial Rivet Nut Drill Sizes
#6-32 and #8-32 Rivet Nut Hole Sizes
The #6-32 and #8-32 are the smallest imperial rivet nut sizes in common use and are well suited to light-duty work, thin sheet metal enclosures, electronic equipment housings, access panels, and anywhere a small machine screw thread needs to be anchored in material too thin to tap reliably. The #6-32 typically calls for a hole in the 0.193–0.196 in range, while the #8-32 steps up to 0.213–0.218 in. As with small metric sizes, the margin for error is narrow. An oversized hole at these dimensions doesn’t take much, a worn drill bit or a wandering entry point can be enough to leave the insert loose. Use a center punch, keep your drill bit sharp, and check the hole diameter before installing.
#10-24 Rivet Nut Hole Size
The #10-24 is a practical small-to-medium fastener size that appears frequently in brackets, equipment panels, access covers, and general fabrication where a #8 feels underbuilt but a 1/4-20 would be unnecessarily large. The common hole range is 0.250–0.265 in, with 17/64 in being the closest fractional drill size at 0.2656 in. It’s a forgiving size to work with — the insert body is large enough to set consistently with standard tooling, and the thread provides solid holding strength for most light and medium load applications.
1/4-20 Rivet Nut Hole Size
The 1/4-20 is one of the most common inch-size rivet nuts across a wide range of industries. You’ll find it in automotive fabrication, trailer builds, general equipment manufacturing, and anywhere a reliable, frequently assembled and disassembled threaded connection is needed in sheet material. The standard hole size falls in the 0.375–0.390 in range, with a 25/64 in drill bit at 0.3906 in being the typical choice. Because 1/4-20 hardware is so widely used, rivet nuts in this size are available in more body styles and materials than almost any other imperial size, giving you good options for matching the insert to the specific demands of the application.
5/16-18 and 3/8-16 Rivet Nut Hole Sizes
The 5/16-18 and 3/8-16 are heavier-duty inch sizes intended for applications with real structural or mechanical load requirements. The 5/16-18 uses a hole in the 0.500–0.515 in range, and the 3/8-16 steps up to 0.625–0.640 in. At these sizes, material thickness becomes a more critical factor, the parent panel needs to be substantial enough to support the insert under load, and the grip range of the rivet nut must be matched carefully to the actual material stack thickness. Installation force requirements also increase, and hand tools may struggle to set these inserts consistently. Proper tooling, correct grip range selection, and appropriate parent material are all more important here than they are at smaller sizes.
Fractional Drill Size vs Exact Hole Diameter
Fractional drill bits are convenient, but they don’t always land exactly on the recommended hole diameter for a given rivet nut. The closest fractional size is often slightly larger than the ideal, and while that gap is usually small, it can matter in practice, particularly in thin material or soft metals like aluminum where the insert has less surrounding material to grip.
For metric rivet nuts, metric drill bits will almost always give you a more accurate hole than fractional equivalents. A 9.0 mm bit cuts a 9.0 mm hole; the nearest fractional option may be a few thousandths larger. That small difference is often acceptable in steel, but in soft aluminum or thin sheet it can be enough to allow movement. When hole accuracy is critical, reaming to the final diameter after drilling is the most reliable approach, producing a cleaner, rounder, more consistent opening than a drill bit alone.
Punched holes behave differently from drilled ones and should be treated separately. The punching process can work-harden the material around the hole edge and leave a slightly different profile than a drilled hole, which affects how the rivet nut body seats and sets. In either case, deburring the hole before installation is always worth doing, a clean edge helps the insert flange seat flush and prevents the burr from interfering with the set.
For example, a rivet nut may call for a hole close to 9.0 mm, but the closest fractional drill size may be slightly larger. That small difference can matter, especially in thin material or soft aluminum.
Rivet Nut Body Style Can Change the Hole Size
Thread size alone doesn’t determine the hole you need. Two rivet nuts with the same thread can have meaningfully different body diameters, body shapes, and hole requirements depending on their design. Always check the specification sheet for the specific insert you’re using, not just the thread size.
Round Body Rivet Nuts
Round body rivet nuts are the most common type and the easiest to install. They accept a standard round drilled hole and work with most rivet nut tools without any special preparation. The tradeoff is spin resistance, a round body in a hole that is even slightly oversized, or in soft material that deforms during setting, can rotate when a bolt is driven in. In most applications this isn’t an issue, but it becomes relevant in soft aluminum, worn holes, or situations where the insert is being set close to the edge of the material.
Knurled Body Rivet Nuts
Knurled body rivet nuts have a serrated or diamond-pattern exterior that bites into the parent material during installation. This mechanical grip significantly improves spin resistance compared to a smooth round body, making them a better choice for soft materials, high-torque applications, or anywhere the bolt will be installed and removed repeatedly. The knurling means the hole tolerance is important, the fit needs to be snug enough for the knurls to actually engage the material rather than just sliding in freely.
Hex Body Rivet Nuts
Hex body rivet nuts require a hex-shaped hole rather than a round one, which means additional tooling for hole preparation, typically a hex punch. In return, they offer the strongest anti-rotation performance of any rivet nut body style, since the flat sides of the hex engage mechanically with the panel regardless of material hardness. They are the right choice for high-torque applications where a round or knurled body cannot be trusted to stay put, and they’re commonly used in automotive and heavy equipment assembly for exactly that reason.
Closed-End Rivet Nuts
Closed-end rivet nuts have a sealed cap on the blind end, blocking the passage through the insert entirely. This makes them useful wherever water, dust, chemicals, or debris intrusion through the fastener hole would be a problem, marine applications, outdoor equipment, and painted or finished panels where a through-hole would compromise the surface. The hole size required for a closed-end rivet nut may differ slightly from an open-end version of the same thread size due to differences in body wall thickness, so check the datasheet rather than assuming the specs are interchangeable.
Countersunk / Flush Rivet Nuts
Countersunk rivet nuts are designed to sit flush with or below the panel surface after installation, leaving no raised flange. This requires not just a drilled hole but a countersunk recess to accept the angled flange hole preparation is a two-step process. They’re used when a flat surface is needed for aesthetic reasons, for clearance, or where a protruding flange would interfere with an mating part. For a full breakdown of insert types, body styles, and when to use each, see our Types of Rivet Nuts guide.
Grip Range and Material Thickness
Hole size is only one part of selecting the right rivet nut. Once you have the correct hole diameter, grip range becomes the next critical variable. Grip range refers to the range of material thickness a specific rivet nut is designed to clamp, and it’s just as easy to get wrong as hole size.
If the material is thinner than the minimum grip range, the rivet nut body will over-collapse before the flange pulls tight against the panel, resulting in a weak, sloppy installation that may feel set but won’t hold under load. If the material is thicker than the maximum grip range, the body won’t collapse far enough to lock behind the panel, and the insert will never set correctly regardless of how much force the tool applies. Material stack-up adds another layer of complexity, if you’re fastening through two panels, a gasket, a coating, or a washer, all of those layers count toward the total thickness the rivet nut needs to span. Paint and surface coatings add thickness too, and a significant burr around a drilled hole can hold the flange slightly off the surface, effectively changing the grip geometry.
How to Measure Before Drilling
Taking a few minutes to work through these steps before drilling saves time, material, and fasteners.
- Measure the material thickness using calipers, not estimation. Account for any coatings, gaskets, or additional layers in the stack.
- Choose the thread size based on the bolt size your application requires and the load it will carry.
- Choose the body style — round smooth, knurled, or hex, based on material hardness, torque requirements, and spin resistance needs.
- Check the manufacturer’s hole size specification for the exact rivet nut you are installing, not just a general chart. Body diameters vary between brands and body styles.
- Select the nearest drill bit to the specified hole diameter, erring toward the tighter end of the tolerance range rather than the loose end.
- Drill a test hole in scrap material of the same thickness and type as your workpiece.
- Deburr the hole on both sides to ensure a clean, flat edge that the flange can seat against properly.
- Install one sample rivet nut using the same tool and setting depth you plan to use in production.
- Test bolt fit, spin resistance, and pull-out strength on the sample before committing to the actual workpiece.
Common Rivet Nut Hole Size Mistakes
Using the Bolt Size as the Hole Size
This is one of the most frequent errors, especially for anyone new to rivet nuts. An M6 bolt does not mean drilling a 6 mm hole. The hole must accommodate the outside body diameter of the M6 rivet nut, which is typically around 9.0 mm, not 6 mm. Drilling to the thread size rather than the body diameter will result in a hole that is far too small for the insert to enter, and attempting to force it through will damage both the rivet nut and the panel.
Ignoring Manufacturer Specs
General hole size charts are useful reference points, but they are not substitutes for the manufacturer’s datasheet. Different brands can use slightly different body diameters for the same thread size, and body style variations, closed-end, large flange, thin-wall, and can shift the required hole diameter further still. When you switch rivet nut suppliers or try a new product line, always verify the specified hole size before drilling.
Drilling Too Large “Just to Make It Fit”
When a rivet nut feels like it’s not going in easily, the instinct is sometimes to open the hole up slightly. This is one of the most reliable ways to end up with a spinning rivet nut. Even a modest increase in hole diameter can be enough to eliminate the grip the insert body needs to resist rotation, particularly in soft materials. If the insert won’t enter the hole cleanly, check whether the hole is correctly sized and deburred before reaching for a larger drill bit.
Not Deburring the Hole
A burr around the hole edge, on either side of the panel, prevents the rivet nut flange from seating flat against the material surface. When the flange can’t seat fully, the clamping force is reduced, the insert may sit at a slight angle, and the finished installation looks and performs poorly. Deburring takes seconds and is always worth doing.
Using the Wrong Body Style
A smooth round body rivet nut is the right tool for many applications, but not all of them. In soft materials like thin aluminum, or in applications where the bolt will be tightened to significant torque or removed and reinstalled frequently, a smooth round body may not provide enough spin resistance to stay put. Choosing a knurled or hex body in these situations isn’t overengineering, it’s selecting the right fastener for the actual conditions.
How to Prevent Rivet Nuts from Spinning
Spinning is the most common rivet nut failure mode and almost always has an identifiable cause. Preventing it comes down to making the right choices before installation rather than trying to correct it after.
Use the correct hole size, tight enough that the insert body has no lateral play before it’s set. Match the grip range to the actual material thickness so the insert collapses properly and locks behind the panel with full clamping force. Choose a knurled or hex body when working with soft materials, high-torque fasteners, or frequently serviced connections where a smooth body can’t be trusted to hold. Avoid over-drilling, even incrementally, since extra clearance consistently leads to spin problems. Set the rivet nut squarely so the collapse is even and the flange seats flat all the way around. Apply the correct installation force for the insert size, undersetting leaves the body only partially collapsed and reduces grip. Finally, test a sample installation before moving to production, checking bolt fit, flange seating, and resistance to rotation under hand torque before committing to the full run.
Rivet Nut Hole Size FAQ
What size hole do I drill for a rivet nut?
It depends on the thread size, body diameter, body style, and manufacturer. The tables in this guide are reliable starting points for the most common sizes, but the final answer always comes from the product datasheet for the specific rivet nut you are installing. Body diameters vary enough between manufacturers and body styles that a general chart alone shouldn’t be the last word before you drill production parts.
Is rivet nut hole size the same as bolt size?
No. The hole size is based on the outside diameter of the rivet nut body, not the bolt thread size. An M6 rivet nut, for example, typically requires a hole close to 9.0 mm, not 6 mm. Confusing thread size with hole size is one of the most common mistakes when working with rivet nuts for the first time.
What happens if the hole is too big?
An oversized hole gives the rivet nut body room to move, which usually means the insert will spin when a bolt is driven in. Beyond spinning, a loose fit can cause the insert to set poorly, sit at an angle, or pull out under load. A hole that looks fine during installation can still be a problem once the joint is put under real stress.
What happens if the hole is too small?
The rivet nut may not enter the hole at all, or it may scrape and deform on the way in. If it does make it through, it may not seat squarely, leaving the flange partially raised and the insert set at an angle. Neither outcome produces a reliable installation.
Can I use a fractional drill bit for metric rivet nuts?
Sometimes, but metric drill bits are generally more accurate for metric rivet nut applications. A fractional bit that is close to the recommended diameter is often slightly oversized, which can matter in soft materials or tight tolerances. Always compare the actual drill diameter to the manufacturer’s recommended hole size before committing to a bit.
Do knurled rivet nuts need a different hole size?
They may. Knurled rivet nuts are designed to grip the hole wall and resist rotation, but that grip depends on the hole being the right size for the knurling to actually engage the material. A hole that is too large defeats the purpose of the knurled body entirely. Check the manufacturer’s specification for the knurled version specifically, since it may differ from the smooth round version of the same thread size.
Do hex rivet nuts use a round hole?
No. Hex rivet nuts require a hex-shaped hole, which means additional tooling, typically a hex punch, for hole preparation. The flat sides of the hex body engage mechanically with the panel to prevent rotation, which is why they offer stronger anti-spin performance than any round body style. A round hole will not provide the mechanical engagement a hex body relies on.
What is the most common rivet nut size?
M5, M6, 1/4-20, and #10-24 are among the most frequently used sizes across a wide range of industries, but there is no single universal answer. The right size depends on the load the joint needs to carry, the thickness and material of the panel, the bolt size your hardware requires, and the available space for the insert body.
Final Thoughts
Hole size is one of the most consequential decisions in a rivet nut installation, and it’s also one of the easiest to get wrong. The charts in this guide give you a solid reference for the most common metric and imperial sizes, but they are a starting point, not a substitute for the manufacturer’s datasheet for your specific insert.
Getting it right means looking at the full picture: hole diameter, grip range, body style, material thickness, and installation tooling all work together. A correctly sized hole paired with the wrong grip range or the wrong body style for the material can still produce a failed installation. Drill a test hole, install a sample, and verify fit and spin resistance before moving to production. That extra step costs minutes and saves the time and frustration of drilling out a spinning insert from a finished part.
Need help estimating a size? Try our Rivet Nut Size Calculator or read our M6 Rivet Nut Hole Size Guide for a detailed example.