You bought a new set of drill bits, loaded one into your impact driver, and… it won’t fit. Or you grabbed a hex-shank bit for your drill press, and it wobbles like it’s about to launch across the shop. Sound familiar?
The problem isn’t your bits or your tools. It’s that different tools use different chuck and collet systems, and nobody bothers explaining which is which. This guide fixes that. By the end, you’ll know exactly which bits fit which tools, when adapters work, and when they’ll get you hurt.
Keyless Chuck: The One You Know
If you own a cordless drill, you own a keyless chuck. It’s the most common chuck type in consumer and professional power tools.
How It Works
Three self-centering jaws tighten around the bit shank when you twist the chuck sleeve. Spring tension holds the jaws in place. No key, no wrench — just grip and twist.
- Single-sleeve: One hand operation. Hold the trigger, twist the chuck with one hand. Most cordless drills use this design because the motor holds the spindle.
- Dual-sleeve: Two rings — hold the back ring stationary and twist the front ring. More common on corded drills where the spindle spins freely.
Capacity: 3/8″ vs 1/2″
The chuck capacity tells you the maximum shank diameter it accepts:
- 3/8″ (10mm) chuck: Found on compact drills, 12V tools, and lighter-duty models. Handles most standard drill bits up to 3/8″ shank diameter. Fine for 90% of homeowner work.
- 1/2″ (13mm) chuck: Standard on full-size 18V/20V drills and hammer drills. Accepts larger shanks, including spade bits and some Forstner bits. Required for serious drilling in wood and masonry.
Key point: Both sizes accept round-shank bits. This is the most versatile chuck type — it grips round, hex, and tri-flat shanks equally well.
Which Tools Use It
- Cordless drills and drill/drivers
- Hammer drills (cordless and corded)
- Drill presses
- Some corded drills
See our top picks: Best Cordless Drills 2026
Keyed Chuck: The Old Guard
Before keyless chucks existed, every drill had one of these. You’ll still find them, and some pros prefer them for good reason.
How It Works
Same three-jaw design as keyless, but a toothed gear key engages teeth on the chuck body. You insert the key, turn it, and the jaws clamp with significantly more force than hand-tightening allows.
Why They Still Exist
- Superior grip: The mechanical advantage of the key means the chuck locks down tighter. Bits are less likely to slip under high torque.
- Drill presses and bench tools: Many drill presses still ship with keyed chucks. The extra grip matters when you’re pushing a Forstner bit through hardwood at controlled speed.
- Heavy drilling: Some industrial drills and hammer drills use keyed chucks because the forces involved would loosen a keyless chuck.
The downside: You lose the key. Everyone loses the key. That’s why manufacturers switched to keyless for handheld tools.
1/4″ Hex Quick-Release: The Impact Driver Standard
This is the one that causes the most confusion, because it looks like it should be compatible with drill chucks. It isn’t — at least not in both directions.
How It Works
A spring-loaded collet grabs the hex-shaped flat surfaces of the bit shank. Pull the sleeve forward, drop the bit in, release — it locks with a click. Pull the sleeve again to release.
- Accepts: Only 1/4″ hex-shank bits and accessories
- Does NOT accept: Round-shank drill bits, larger hex shanks, or SDS bits
- One-handed bit changes: The whole point of this system. On a jobsite, you’re swapping bits constantly. Speed matters.
Why Impact Drivers Use Hex
Impact drivers deliver torque in rapid rotational hammer blows. A three-jaw chuck would loosen under that pulsing force. The hex collet system grips the flat surfaces positively — the bit physically cannot spin inside the holder. This is a mechanical necessity, not just convenience.
Which Tools Use It
- Impact drivers (all of them)
- Some drywall screw guns
- Quick-change drill attachments
- Many multi-bit screwdrivers
Important: You CAN put a 1/4″ hex-shank bit into a drill chuck — the chuck jaws will grip the hex shape just fine. But you CANNOT put a round-shank drill bit into a hex collet. This is a one-way compatibility.
For more on impact drivers: Best Impact Drivers 2026
SDS-Plus: Built for Hammering
If you’ve ever tried to drill into concrete with a regular drill and a masonry bit, you know it’s slow, frustrating, and murder on the tool. SDS-Plus exists because concrete demands a completely different approach.
How It Works
SDS stands for Steck, Dreh, Sitz (German: insert, twist, seated) — though Bosch, who invented it, also calls it the Slotted Drive System. The shank has two sets of grooves:
- Two open grooves that guide the bit into the chuck and allow it to slide back and forth (this is crucial for the hammering action)
- Two closed grooves that lock ball bearings in place to prevent the bit from falling out
The bit can move about 1cm in and out of the chuck while locked in. This sliding motion is what allows the tool’s internal piston to hammer the bit into the material independently of the rotation. It’s a fundamentally different mechanism from a hammer drill, which just vibrates.
SDS-Plus Specs
- Shank diameter: 10mm
- Typical bit sizes: 4mm to 30mm diameter
- Used in: Rotary hammers (the compact ones you can hold with one or two hands)
- Impact energy: 1.5 to 5+ joules depending on tool size
The Bosch GSB18V (check price on Amazon) is an example of a modern hammer drill with a standard chuck — it vibrates, but doesn’t have true SDS hammering. For concrete work beyond occasional anchor holes, you want a dedicated SDS-Plus rotary hammer.
Cannot Use Regular Bits
SDS chucks only accept SDS-shank bits. You cannot put a round-shank masonry bit into an SDS chuck. However, you can get SDS-to-keyless chuck adapters (more on that below).
SDS-Max: When SDS-Plus Isn’t Enough
SDS-Max is the bigger, heavier version of SDS-Plus, designed for serious demolition and large-diameter concrete drilling.
How It Differs from SDS-Plus
| Spec | SDS-Plus | SDS-Max |
|---|---|---|
| Shank diameter | 10mm | 18mm |
| Number of grooves | 4 (2 open + 2 closed) | 5 (3 open + 2 closed) |
| Typical bit sizes | 4-30mm | 12-52mm |
| Impact energy | 1.5-5 joules | 5-20+ joules |
| Tool weight | 3-8 lbs | 10-25 lbs |
| Typical use | Anchors, small holes in concrete | Core drilling, chiseling, demolition |
Who needs SDS-Max? If you’re installing drop-in anchors, running conduit through concrete walls, or doing demolition work. Most homeowners and general contractors are fine with SDS-Plus.
SDS-Plus and SDS-Max are NOT interchangeable. The shanks are completely different sizes. There are no adapters — you need the right bits for the right tool.
Router Collets: Precision Grip for High RPM
Routers spin at 10,000-30,000 RPM. At those speeds, even a tiny amount of wobble (runout) creates visible imperfections in your cut. That’s why routers use collets instead of chucks.
How Collets Work
A collet is a thin-walled metal sleeve that compresses evenly around the bit shank when a nut is tightened. Unlike a three-jaw chuck that contacts the bit at three points, a collet grips the entire circumference. This gives better concentricity (less wobble) and more secure grip at high speeds.
1/4″ vs 1/2″ Router Collets
- 1/4″ collet: Standard on trim routers and compact routers. Accepts 1/4″ shank router bits only. Good for edge profiles, small roundovers, and light template work.
- 1/2″ collet: Standard on full-size routers. Accepts 1/2″ shank bits, which are stiffer, vibrate less, and can handle deeper cuts. Many 1/2″ routers include a 1/4″ collet adapter.
Never use a sleeve adapter to put a 1/4″ bit in a 1/2″ collet. Cheap adapters introduce runout, and at router speeds, that means poor cuts at best and a thrown bit at worst. Use the correct collet size for your bit shank.
For more on router bit selection: Router Bits for Beginners Guide
The Compatibility Matrix
This is the table to bookmark. It tells you what fits where.
| Chuck/Collet Type | Accepts Round Shank | Accepts 1/4″ Hex | Accepts SDS | Tools That Use It |
|---|---|---|---|---|
| Keyless Chuck (3/8″) | Up to 3/8″ | Yes | No | Compact drills, 12V drills |
| Keyless Chuck (1/2″) | Up to 1/2″ | Yes | No | Full-size drills, hammer drills |
| Keyed Chuck | Up to rated size | Yes | No | Drill presses, some corded drills |
| 1/4″ Hex Collet | No | Yes (1/4″ only) | No | Impact drivers, screw guns |
| SDS-Plus | No | No | SDS-Plus only | Compact rotary hammers |
| SDS-Max | No | No | SDS-Max only | Heavy rotary hammers, demo hammers |
| Router Collet (1/4″) | 1/4″ only | No | No | Trim/compact routers |
| Router Collet (1/2″) | 1/2″ only | No | No | Full-size routers |
The golden rule: A keyless drill chuck is the most versatile — it accepts both round and hex shank bits. Every other system is more restrictive but optimized for its specific job.
Adapters: When They Work and When They’re Dangerous
Adapters exist for most chuck/collet conversions. Some are perfectly fine. Others are asking for trouble.
Safe and Useful Adapters
- SDS-Plus to keyless chuck: Snaps into your rotary hammer and gives you a drill chuck on the end. Works well for light drilling in wood or metal when you don’t want to grab a second tool. Not for hammering — the adapter can’t handle the percussion forces.
- 1/4″ hex to 3/8″ or 1/2″ socket: Lets your impact driver use socket wrench attachments. Common and useful for automotive and assembly work.
- 1/4″ hex shank drill bits: Not adapters exactly, but drill bits manufactured with hex shanks so they fit impact drivers directly. These work great for occasional drilling. Available in most common sizes.
Use With Caution
- Keyless chuck on impact driver (hex-to-chuck adapter): Technically works, but the impact mechanism will loosen the chuck over time. Fine for quick light drilling; don’t rely on it for heavy use.
- Collet reducers (1/2″ to 1/4″ for routers): Quality varies enormously. A precision-machined reducer from the router manufacturer is usually fine. A $5 no-name sleeve from the bargain bin introduces dangerous runout at 25,000 RPM.
Never Use
- SDS-Plus bits in a regular chuck: Even if you could jam one in, the grooves prevent proper gripping. The bit will slip, wobble, and potentially fly out.
- Round-shank bits in an impact driver (using a chuck adapter) for heavy work: The three-jaw grip will loosen under impact forces. The bit will spin in the chuck, scoring the shank and potentially launching the bit.
- Anything above the adapter’s rated RPM or torque: Every adapter introduces a weak point. Exceeding its limits turns it into a failure point, and at power tool speeds, failure means projectiles.
Quick Reference: “My Bit Won’t Fit” Troubleshooting
Before you blame the bit or the tool, check this list:
- Hex bit won’t go into impact driver: Check if it’s 1/4″ hex. Some specialty bits use different hex sizes (5/16″, etc.). Also check that the collet sleeve is pulled forward fully.
- Drill bit wobbles in chuck: The chuck may be worn, or you’re using a bit with a shank diameter much smaller than the chuck capacity. Use the right size range.
- SDS bit won’t lock in: Make sure you’re pushing it in straight and twisting slightly. The ball bearings need to engage the grooves. If it still won’t click, clean the chuck — concrete dust jams the mechanism.
- Router bit shank feels loose: You might have a 1/4″ bit in a 1/2″ collet or vice versa. Measure the shank. Never assume.
- Bit slips under load: Your chuck needs tightening (or replacement if it’s worn). For keyed chucks, use the key in all three tightening holes, not just one.
Start with the right bits for your tools: Best Drill Bit Sets 2026
FAQ
Can I use regular drill bits in an impact driver?
Only if the drill bits have a 1/4″ hex shank. Round-shank bits won’t fit in an impact driver’s collet. You can buy hex-shank drill bit sets specifically designed for impact drivers, and they work well for occasional drilling. For heavy drilling, use a drill with a proper chuck.
What’s better for a drill press: keyed or keyless chuck?
Keyed chucks grip tighter and are better for large bits, Forstner bits, and heavy feed pressure. Many drill press users prefer keyed chucks because bit slipping in a drill press is both wasteful and dangerous. If your press came with keyless, it’s fine for most work, but consider upgrading to keyed if you’re doing a lot of hardwood boring.
Why do impact drivers only use hex bits?
The hammering mechanism delivers torque in sharp rotational pulses. A three-jaw chuck would gradually loosen under these forces and eventually release the bit. The hex collet locks onto the flat surfaces mechanically — the bit literally cannot rotate inside the holder regardless of the impact forces.
Can I use SDS-Plus bits in an SDS-Max tool?
No. The shank diameters are completely different (10mm vs 18mm), and the groove patterns don’t match. There are no reliable adapters for this conversion. You need the correct bit type for your tool.
Do I need both a drill and an impact driver?
For most people, yes. They’re designed for different jobs. A drill with a keyless chuck handles drilling holes (round-shank bits, Forstner bits, hole saws). An impact driver with a hex collet handles driving fasteners quickly and with less wrist fatigue. A combo kit with both tools is the best value entry point.
Why do router bits come in 1/4″ and 1/2″ shank?
The 1/2″ shank is stiffer, which reduces vibration and deflection during cuts. This produces cleaner results, especially on large profile bits or deep cuts. The 1/4″ shank is lighter and fits compact routers. When a bit is available in both sizes, always choose 1/2″ if your router accepts it.
How do I know when my chuck is worn out?
Three signs: bits slip under moderate load even when the chuck is tightened fully, bits wobble visibly when spinning (excessive runout), or the chuck won’t tighten at all and feels “crunchy.” Chucks are replaceable on most drills — it’s a standard maintenance item, not a reason to buy a new tool.
What about spline-shank systems?
Spline shanks were an alternative to SDS-Max used primarily by Bosch and some other manufacturers for mid-size rotary hammers. They’re largely obsolete now, replaced by SDS-Max across the industry. If you inherit a spline-shank tool, bits are still available but the selection is shrinking. For new purchases, stick with SDS-Plus or SDS-Max.
