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Best Drill Bits for Drilling Out Locks: Choose for the Lock, Not Just the Price
For authorized removal of a lock you own or are permitted to service, a cobalt-alloy HSS bit is the best general-purpose choice for drilling through a hard steel pin; use a sharp, short, high-speed-steel (HSS) bit for softer brass or aluminum, and a carbide-tipped masonry bit only when the lock’s construction calls for it. The right size and controlled speed matter as much as the material: an oversized or overheated bit can damage the door, cylinder housing, or nearby hardware before it removes the lock.
Quick comparison by material and situation
Lock cylinders vary. Pins may be brass or steel, while the plug and housing can include harder alloys or hardened inserts. A drill bit’s coating alone does not make it suitable for every part. Check the lock manufacturer’s service information where available, and stop if you encounter unexpected resistance; a locksmith can often remove a lock with less collateral damage.
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| Bit type | Common sizes to consider | Best suited to | Trade-off | Buying guidance |
|---|---|---|---|---|
| HSS, standard point | 1/8 in (3.2 mm), 3/16 in (4.8 mm), 1/4 in (6.4 mm) | Brass, aluminum, and other relatively soft components | Inexpensive, but edge life falls quickly on hard steel | Choose a sharp, accurately ground bit for occasional work |
| Cobalt-alloy HSS, often M35 | 1/8 in (3.2 mm), 3/16 in (4.8 mm), 1/4 in (6.4 mm) | Harder steel components and repeated maintenance work | Costs more; still dulls if overheated or forced | Look for a clearly stated cobalt grade, not just a gold-colored finish |
| Carbide-tipped bit | Sizes depend on the lock and bit style; verify the shank and tip dimensions | Specific hard materials when the bit maker rates it for the application | Brittle tip can chip from wobble, side loading, or impact | Use only with a stable setup and a compatible drill; avoid treating it as a universal upgrade |
| Black-oxide HSS | 1/8 in (3.2 mm), 3/16 in (4.8 mm), 1/4 in (6.4 mm) | General drilling in softer metals and routine shop use | Surface treatment is not a substitute for a harder cutting alloy | A sensible budget option when the lock does not contain hardened steel |
These are common pilot-bit sizes, not a universal lock-removal recipe. The appropriate diameter depends on the cylinder design and the intended service procedure. Do not assume that a larger bit is faster or safer.
Which bit should you buy?
- One lock, uncertain construction: Start with a quality cobalt-alloy HSS bit set that includes small increments, rather than a single large bit. It gives you options without forcing a jump to an oversized cutter.
- Known brass or aluminum components: Sharp standard HSS is usually adequate and more economical. A split-point tip can help it start accurately on a prepared, flat surface.
- Frequent locksmith or facilities work: Choose cobalt-alloy HSS bits in replaceable sizes and keep spares. Paying more for a bit that holds its edge can be worthwhile when it prevents repeated interruptions.
- Hardened or unfamiliar lock: Don’t buy carbide solely because the lock is difficult. Confirm the lock’s construction and the bit’s intended material rating; if the procedure is unclear, ask a locksmith.
- Limited access near a door or trim: Favor a short, rigid bit and a drill with good low-speed control. A long bit can flex or wander, increasing the chance of marking surrounding hardware.
Tip design, speed, and heat
Point geometry affects control
A standard 118-degree point is common and works well for many general-purpose bits, but it can skate on a smooth curved surface. A 135-degree split point is more self-centering on suitable materials and often needs less pressure to begin cutting. Neither geometry compensates for a dull edge or an unstable drill. Avoid a bit that is visibly chipped, bent, or blunt.
Use controlled speed rather than maximum speed
Metal drilling generates heat at the cutting edges. Excessive speed, heavy pressure, or a bit that rubs instead of cutting can quickly soften the cutting edge and shorten its life. Use the bit manufacturer’s speed guidance for the material and diameter. In general, larger bits and harder materials call for lower speed. Keep the drill square to the work, use steady moderate pressure, and let the flutes clear chips. If the bit squeals, smokes, or stops producing chips, pause and reassess instead of pressing harder.
A cutting lubricant rated for metalworking can reduce friction on appropriate steel work. Apply it sparingly and follow the lock and bit makers’ guidance; keep liquids away from electrical components and finishes that could be stained. Never cool a hot bit abruptly with water: thermal shock can damage a bit, and hot chips can cause injury.
Protect the door and nearby hardware
Before starting, confirm authorization, identify the lock type, and check for a documented non-destructive removal method. Protect nearby paint, trim, glass, and escutcheons with a rigid shield or masking material that will not interfere with the drill. Keep the drill’s body and chuck clear of the door surface, and avoid letting a long bit contact the cylinder surround. Wear eye protection; metal chips are sharp. Remove loose jewelry and secure hair and clothing.
Clamp or otherwise stabilize the work only where doing so will not damage the door or lock. Keep the bit aligned, and stop if the lock begins to shift or the drill binds. Don’t use an impact driver for precision metal drilling: repeated impacts can break brittle tips, reduce control, and damage the lock or door. If the cylinder is part of a fire-rated, security, or access-control assembly, use a qualified technician and preserve any required hardware.
A practical bit-selection and care routine
- Identify the assembly. Find the lock model or service instructions if possible. Determine whether the relevant material is soft metal, steel, or a hardened insert.
- Match the bit to the material. Use HSS for softer components and cobalt-alloy HSS for harder steel when the bit maker supports that use. Treat carbide as a specialist choice, not a default.
- Check the fit and condition. Confirm that the shank fits the drill securely and that the bit is straight and sharp. A loose chuck or damaged tip invites wandering.
- Set up for control. Protect the surrounding finish, use a stable stance, and select a low, controllable speed. Follow the manufacturer’s procedure and stop if the result differs from what it describes.
- Clean and inspect afterward. Let the bit cool naturally, brush chips from its flutes, and wipe away lubricant. Store it dry in a case so cutting edges do not rub against other bits.
In regular use, the cutting edge usually wears first; heat discoloration, rounded edges, and difficulty producing clean chips are signs to retire or professionally sharpen the bit. Don’t keep drilling with a dull bit in the hope that more pressure will restore its cut. That common mistake creates more heat, damages the work, and may turn a replaceable consumable into a broken bit.
Bottom line
For most authorized lock-service work, a small set of sharp cobalt-alloy HSS bits offers the most useful balance of durability and versatility, while ordinary HSS is a budget-conscious pick for known soft-metal components. Choose the shortest practical bit, use a size specified by the lock’s service procedure, and manage heat with controlled speed and pauses. If the lock’s materials or removal method are uncertain—or the surrounding door hardware is valuable—a locksmith is often the safer and less costly choice.