Walk into any power tool aisle and you’ll see drill bits in two main flavours: round shanks and hex shanks. They look different, they fit different tools, and using the wrong one in the wrong drill is a quick way to waste money or damage your tool.
This guide tells you which is which, what tools they fit, and when you actually need to care about the difference.
Hex Shank vs Round Shank — Quick Comparison
| Feature | Round Shank | Hex Shank (1/4″) |
|---|---|---|
| Shape | Cylindrical, smooth | Six-sided, flat faces |
| Standard Size | Various (2mm, 3mm, 4mm, etc.) | 1/4″ (6.35mm) — universal |
| Fits What Tools | Standard 3-jaw chucks (most drills) | Impact drivers, quick-change chucks, some modern drills |
| Slipping Under Load | Can slip if chuck jaws aren’t tight enough | Won’t slip—hex locks into collet securely |
| Bit Change Speed | Moderate (chuck key needed on older models) | Fast (one-handed, keyless) |
| Bit Size Range | Wide (1mm to 50mm+ available) | Limited (typically 2mm to 13mm diameter) |
| Best For | All drilling tasks, general use | Fastening, impact driving, production work |
| Price | Cheapest | Slightly more expensive |
Round Shank Drill Bits — The Standard
Round shank bits are the most common type by far. They have a smooth, cylindrical shaft that tapers to the business end (the cutting lips). They fit into a 3-jaw chuck—that’s the rotating collar on the front of a standard drill or drill press.
Why Round Shanks Dominate
- Universal: Nearly every corded drill, cordless drill, bench drill, and industrial drill has a 3-jaw chuck that accepts round shanks
- Size range: Available from 0.5mm (tiny jeweller’s work) up to 50mm+ diameter
- Cheap: Because they’re so common, round shank bits are the most affordable option
- Proven: Over a century of drill bit history—no surprises
The Slipping Problem
Round shank bits have one weakness: if your chuck jaws aren’t gripped tightly, the bit can slip under load. This is especially true with older drills that have worn chuck jaws or cordless drills running on low battery power.
Solution: tighten your chuck hard. Modern chuck keys have a spring-loaded mechanism to prevent over-tightening, but older manual chucks need firm hand pressure.
Round Shank Sizes
Round shanks come in metric and imperial sizes: 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 16mm, 20mm, and so on. Most home and trade drills have a max chuck capacity of 13mm (1/2 inch), though drill presses often go larger.
Buy round shank bit sets on Amazon.
Hex Shank (1/4″) Drill Bits — Fast Bit Changes
Hex shank bits (also called six-flute or six-sided shanks) have a six-sided shaft that fits into a quick-change collet. The industry standard is 1/4″ (6.35mm) across all brands and all tools.
Why Hex Shanks Caught On
- Won’t slip: The hex geometry locks securely into the collet. No tightening needed; just push and twist slightly to lock
- One-handed: Change bits without a chuck key, even while the drill is running (though don’t do that)
- Speed: Perfect for production work or jobs where you change bits constantly
- Impact-rated: Hex bits are designed to handle the vibration and shock of impact drivers
- Universal across brands: A 1/4″ hex bit from one manufacturer works in any 1/4″ quick-change chuck from any brand
The Size Limitation
The downside of hex shanks is that they’re typically only available up to about 13mm diameter. If you need to drill a 20mm hole or larger, you’ll need a round shank bit or a spade bit or hole saw.
Hex shank bits are most common for fastening work (pilot holes before screwing), general metal drilling, and impact driving.
Buy hex shank bit sets on Amazon.
Can You Use Hex Shank Bits in a Round-Shank Chuck?
Yes, you can—and it works fine.
A 1/4″ hex shank will fit into a standard 13mm 3-jaw chuck. The jaws grip the flat faces of the hex and hold it securely. It’s not the most elegant solution, but it works in a pinch.
However, there’s no advantage to doing this. You lose the benefit of quick bit changes, and you might as well just use a round shank bit instead. That said, if you’ve only got hex bits on hand and need to drill something, it’s perfectly safe.
Can You Use Round Shank Bits in an Impact Driver?
No. Do not do this.
Impact drivers have a 1/4″ quick-change hex collet. Round shank bits won’t fit. Even if you tried to force one in somehow, the impact shock of the driver would damage the bit and the chuck.
If you want to use your impact driver for drilling, use hex shank bits or a compatible hex adapter. For larger holes or precision work, use a standard drill with round shank bits instead.
Three-Flat Shanks — The Compromise
In recent years, some manufacturers have introduced three-flat shank bits as a middle ground. These have three flat faces cut into a roughly cylindrical shank, which prevents slipping in a standard chuck while still looking more like a traditional bit.
They’re less common than either round or hex, but they’re worth knowing about if you’re shopping around. They fit standard chucks but with better grip than smooth round shanks.
When to Use Each Type
Use Round Shank Bits If You Have:
- A standard corded or cordless drill with a 3-jaw chuck
- A drill press
- Jobs that need large-diameter holes (over 13mm)
- A mix of drilling tasks and limited budget
- Older, traditional drills
Use Hex Shank Bits If You Have:
- An impact driver (these exclusively use 1/4″ hex)
- A modern cordless drill with a quick-change chuck
- Production or fastening work where you change bits constantly
- A job that needs consistent, fast bit changes
- Emphasis on convenience over size range
Impact-Rated Hex Bits
Not all hex bits are created equal. Impact-rated hex bits are specially designed to handle the rapid percussion of an impact driver without breaking. They have a tougher core and sometimes special absorbing layers to dissipate shock.
If you’re using an impact driver for drilling or driving, buy impact-rated bits. Standard hex bits can break under the impact shock, especially in hard materials.
Buy impact-rated hex bit sets on Amazon.
Building Your Drill Bit Toolkit
Most professionals have both. Keep a set of round shank bits for your standard drill or drill press—they’re cheap and cover every size. Keep a set of hex shank bits for your impact driver and quick-change drill.
If you’re buying your first toolkit and only have budget for one, start with round shanks. They work in almost any drill and are the safest bet for general work.
For specialist work, consider HSS vs cobalt materials and brad-point vs twist-vs-spade designs once you’ve nailed down the shank type you need.
Watch: Video Guide
Frequently Asked Questions
Is 1/4″ hex the same across all brands?
Yes. The 1/4″ hex shank is an industry standard. A Makita hex bit fits a DeWalt quick-change chuck, which fits a Milwaukee impact driver, etc. Universal compatibility is one of the main advantages of hex shank standardisation.
What does the shank size mean?
The shank is the part that fits into the chuck. For round shanks, shank size directly relates to the bit diameter (a 5mm bit has roughly a 5mm shank). For hex shanks, shank size is always 1/4″ (6.35mm) regardless of the drill diameter.
Can I sharpen hex shank bits?
Yes, just like round shank bits. If the cutting lips wear down, you can hone them back on a grindstone or have them professionally sharpened. The hex shank itself doesn’t wear easily unless you’re using an incorrectly sized collet.
Why are hex bits more expensive?
They’re not dramatically more expensive, but hex bits are often impact-rated (tougher manufacturing), sold in smaller kits (higher per-bit cost), and target professional users willing to pay more for convenience. Round shank bits are sold in bulk to DIYers, which drives the price down.
Do I need impact-rated bits for an impact driver?
Technically, standard hex bits can work in an impact driver for light work. But for any serious use—fastening into hardened materials or continuous production work—impact-rated bits are essential. They won’t break as easily and last much longer.
What’s the largest hex shank bit available?
Most commonly, 13mm (1/2 inch) diameter is the largest you’ll find in 1/4″ hex shank. Speciality bits can go up to 16mm or occasionally larger, but they become rarer and more expensive. For larger holes, switch to spade bits, hole saws, or a standard drill with round shank bits.
