Cold Chisels: The UK Guide to Cutting Metal and Masonry by Hand
What a cold chisel is, how it differs from a bolster and plugging chisel, why you must pair it with a club hammer, and what to buy from £3 upwards.
You're halfway through tiling a utility room and one stubborn ridge of old adhesive refuses to scrape off. A cold chisel and two taps of a club hammer would pop it off in under a minute. Instead you reach for a wood chisel because it's what's in the drawer. The edge folds over on the first strike, you've ruined a fifteen-pound tool, and the adhesive is still there. Cold chisels cost less than a pint and every tool kit should have one. But most homeowners buy the wrong chisel for the job, pair it with the wrong hammer, and ignore the one maintenance step that stops it becoming a hazard.
What a cold chisel actually is
A cold chisel is a hardened steel bar with a narrow bevelled blade at one end and a flat striking face at the other. "Cold" means it's used on unheated metal, as opposed to a blacksmith's chisel used on glowing-hot steel at the forge. The blade is typically 6mm to 25mm wide, the shank is hexagonal or octagonal to stop it rolling off surfaces, and the whole tool is drop-forged from carbon steel or chrome vanadium alloy. The cutting tip is hardened and tempered so it can bite into mild steel, bolts, nails, mortar, tile adhesive, and masonry without folding over. The body is deliberately left slightly softer so it absorbs hammer blows without shattering.
That differential hardness is the whole point of the tool. A wood chisel has a razor-thin bevel of 15 to 30 degrees, brilliant for paring softwood but fragile. A cold chisel has a blunter 60 to 70 degree bevel, which is what lets it survive repeated hammer strikes onto masonry and steel. Use a wood chisel on a nail and you'll fold the edge on the first hit. Use a cold chisel on a dovetail joint and you'll crush the timber.
On a kitchen extension, the cold chisel earns its keep in half a dozen small jobs that would be miserable without it. Trimming a protruding holding-down bolt flush so the sole plate sits flat. Cutting a rusted fixing out of a brick when you can't unscrew it. Popping off individual broken tiles before re-tiling. Scraping hardened tile adhesive off a substrate before plastering. Cutting through a rebar offcut that's sticking up from a strip foundation. Small, specific, repeated tasks where a power tool would be overkill.
The three-way confusion (and why it matters)
Beginners mix up three chisels that look superficially similar in the shop but do different jobs. Buying the wrong one means the tool either doesn't work or blunts itself within minutes. Here's the distinction in one table.
| Tool | Blade width | Hardness | Use it for | Do not use it for |
|---|---|---|---|---|
| Cold chisel | 6-25mm narrow | Fully hardened cutting edge | Cutting mild steel, bolts, nails, rebar; chopping tile adhesive; trimming small masonry fixings; detail work in mortar | Splitting full bricks cleanly (too narrow for a single-pass fracture) |
| Bolster chisel | 57-114mm wide | Softer steel, not fully hardened | Splitting bricks and blocks; chasing cable routes in plaster and masonry; removing large floor tiles | Any metal cutting. A bolster will blunt on the first strike against a rebar or nail. |
| Plugging chisel | 6-10mm narrow with fluted groove | Hardened cutting tip | Raking old mortar out of brick joints during repointing. The groove lets debris escape. | General metal cutting or brick splitting. It is a specialist mortar tool. |
The practical rule: narrow and fully hardened means cold chisel, narrow and fluted means plugging chisel, wide and softer means bolster. If the tool has a 75mm or 100mm blade, it will not cut steel. If the tool has a 13mm blade, it will not split a brick cleanly. Most builders' merchants sell "chisel and bolster sets" that bundle one of each, which is the right purchase if you only want to shop once.
On a repointing job around the junction of a new extension and an existing house wall, a plugging chisel will give you cleaner joints than a cold chisel because its narrow fluted profile tracks the mortar bed without chipping the surrounding brick arrises. Several UK forum threads on period brickwork repointing make the same point: experienced DIYers reach for the plugging chisel first. The cold chisel comes out for the trickier spots and for cutting any embedded metal wall ties or nails you find in old mortar.
Sizes and what each one is for
Cold chisels are sold by overall length and blade width. The sizes you're likely to see on UK shelves cluster around four useful ranges.
| Length | Blade width | What it's for |
|---|---|---|
| 150mm (6") | 6-13mm | Detail work in tight spots, light mortar chopping, cutting small nails or tacks flush. The chisel for finesse jobs. |
| 200mm (8") | 13-19mm | General mortar raking and chopping, clearing tile adhesive, cutting small fixings. A comfortable all-round size. |
| 250-300mm (10-12") | 19-25mm | The single most useful size. Cuts rebar, trims bolts, chops out stubborn tile, works mortar joints. Buy this first. |
| 350-457mm (14-18") | 25mm | Heavy work. Cutting bigger rebar, breaking concrete edges during demolition, working deep into joints. Overkill for a typical extension. |
For an extension build, buy the 250mm or 300mm with a 19-25mm blade. It's the size that does 90% of the jobs and fits comfortably in one hand while you strike it with the other. A second 150mm chisel is worth adding if you expect to work in tight corners or pick at detail, but it's a nice-to-have rather than essential.
How to use a cold chisel properly
Hitting a chisel with a hammer looks obvious. It isn't. The difference between a clean chop and a shattered mess is technique, and the difference between a healthy hand and a broken finger is the hammer you choose.
The striking partner: always a club hammer or ball peen
The correct tool to strike a cold chisel is a club hammer (also called a lump hammer, typically 1kg to 2kg) for masonry work, or a ball peen hammer (engineer's hammer) for metal cutting. Both have striking faces that are heat-treated to match the hardness of a chisel's striking head. The impact is clean, the energy transfers straight down the shaft into the cutting edge, and neither tool damages the other.
Never strike a cold chisel with a claw hammer. This is not a convention or a style preference, it is a real safety hazard. A claw hammer's head is heat-treated for a different purpose: driving nails into timber. The face is harder and more brittle than a club hammer's striking face, and striking hardened steel with a brittle face can chip the hammer itself. Those chipped fragments fly at high velocity. The narrow face of a claw hammer also concentrates force unevenly, which accelerates mushrooming of the chisel head. Two separate hazards from one mistake.
Match the hammer weight to the chisel. A 150mm chisel needs a 1kg (2lb) club. A 250-300mm chisel pairs well with a 1.1kg (2.5lb) club, which is the standard size you'll see in every UK merchant. For heavy rebar cutting with a 300mm+ chisel, step up to 1.4kg (3lb). Too heavy a hammer on a small chisel means you overpower the cut and lose accuracy. Too light a hammer on a big chisel means fifty strikes instead of ten.
Technique
Immobilise the workpiece
A chisel only cuts what can't move. Clamp the workpiece in a vice for metal cutting. For masonry or floor work, make sure the material is supported on a solid surface (not a springy one) and can't rock or skip. If you're cutting a bolt or nail, hold the chisel as vertically as possible so the strike drives straight down.
Grip the chisel loosely
Hold the chisel between thumb and first two fingers, wrapped around the shank below the overstrike guard. Your grip should be firm enough to control the angle but loose enough that if the hammer glances off-centre and hits the chisel instead of the strike face, the chisel moves rather than driving the shock straight into your hand bones. Experienced bricklayers let the chisel fly out of their hand rather than grip tightly through a mis-hit.
Set the cutting angle
For cutting mild steel (bolts, nails, rebar), hold the blade at 60 to 70 degrees to the work. For shaving metal off a surface, drop to 45 degrees. For raking mortar from a joint, 30 to 45 degrees. For popping off a broken tile, slide the blade beneath the tile edge at 30 to 45 degrees and strike lightly. The angle matters: too steep and the blade digs in and stops, too shallow and it skates across the surface.
Strike from the elbow, not the shoulder
Keep the hammer swing short and controlled, from the elbow. Look at the chisel head, not the work. Swing through the head, not at it. A firm, confident strike with a 2.5lb club will chop 6mm rebar in two or three blows. Timid taps just work-harden the steel and make the cut harder.
Oil the blade for metal work
For cutting sheet metal or steel rod, a smear of light machine oil on the cutting edge reduces friction, keeps the edge cooler, and gives a cleaner cut. A cold chisel used dry on repeated metal cuts will heat up at the tip. Heat is what softens hardened steel and kills the edge. Oil is a two-second step that adds years to the chisel's working life.
For tile removal, grout removal before re-tiling, or breaking off hardened adhesive, the angle is shallow (30 to 45 degrees) and the strike is light. You are trying to break the adhesive bond, not shatter the substrate underneath. Several short taps produce a cleaner result than one heavy blow, which often cracks the plaster or concrete you are working onto.
The mushroomed head: the one maintenance step everyone skips
This is the single most important thing to know about owning a cold chisel. Every time you strike the head, the metal spreads slightly outward. Over dozens or hundreds of strikes, the top of the chisel develops a flared rim, a lip of work-hardened steel that overhangs the original shank diameter. This is called "mushrooming." The flared edges are brittle. Under impact, fragments snap off and fly at speeds that embed them in skin and, if unlucky, in eyes. HSE guidance on struck tools makes this explicit: do not allow chisel heads to spread to a mushroom shape, grind off the sides regularly.
Forum users on UK DIY boards and stone-carving sites have first-hand accounts of metal shards driven into fingers from mushroomed chisels, including one account of a fragment leaving a permanent mark. This is not a theoretical risk. It is why every cold chisel guide written by someone who has actually worn the consequence treats mushrooming as the maintenance step, not sharpening.
Dressing a mushroomed head
This takes under a minute and prevents the worst injury a cold chisel can cause.
Put on safety goggles, not just glasses
Safety goggles that seal around the eye are safer than open-sided safety spectacles for this job. Grinding produces its own metal fragments.
Use a bench grinder or angle grinder with a grinding disc
A bench grinder is the proper tool. An angle grinder with a metal grinding disc works if that's what you have. Do not use a cutting disc, it can shatter under side load.
Grind the top flat, with 45-degree chamfered sides
Hold the chisel at about 45 degrees to the face of the wheel. Grind the mushroomed metal off, rotating the chisel and moving it across the wheel face so you don't gouge a groove in the wheel. Work down until the top is flat and square to the shaft, with the sides chamfered at roughly 45 degrees.
Cool in water every 10 to 15 seconds
This is the step that matters most. If the steel turns straw-yellow or blue during grinding, it has overheated and lost its temper. A de-tempered striking end will soften and mushroom faster than before, and the hardness gradient down the shaft is destroyed. Dip the chisel in a tub of cold water between short bursts of grinding. If you see blue discolouration, stop, cool it fully, and grind more gently on the next pass.
Add a 45-degree bevel to the striking face
Finish with a light chamfer all the way round the top edge. This small bevel delays the formation of the next mushroom because there's no sharp corner for metal to spread from. You still need to inspect the head regularly, but the interval between grindings gets longer.
Check the striking head before every session of chisel work. If you can see the metal flaring out beyond the shaft diameter, or any hairline cracks forming at the rim, dress the head before you strike it again. A thirty-second job at the grinder prevents a trip to A&E.
Mandatory PPE
Four items, every time you pick up a chisel. Not optional, not situational.
Safety glasses or goggles to EN 166 impact rating. Cold chisel work throws three separate projectile hazards: masonry chips, metal shards from the work material, and potential fragments from a mushroomed head. Any one of them can blind you. Look for the "F" marking on the lens, which certifies impact resistance at EN 166 grade speeds. Decent impact-rated safety glasses cost around £3 from any builders' merchant. Goggles that seal around the eye socket (around £6) are safer when working overhead or in dusty conditions.
Work gloves. A missed hammer strike hits the hand holding the chisel. Gloves won't stop a serious blow but they absorb glancing ones and protect against sharp brick edges, rust flakes, and the chisel's own shaft. Rigger gloves or general-purpose builders' gloves around £4 are enough.
Long sleeves. Metal fragments that don't hit your eyes or hands hit your forearms. A long-sleeved work shirt or overall reduces the number of small cuts you carry away from a chiselling session. This matters more than it sounds when you're working overhead or at shoulder height and debris falls on you.
FFP3 dust mask for sustained masonry work. Chiselling mortar or tile adhesive releases respirable crystalline silica. COSHH Regulations 2002 apply to any sustained exposure. A session of a few minutes is usually fine with good ventilation, but anything longer in an enclosed space needs an FFP3 mask.
What to buy
Cold chisels are cheap tools. Even the best guarded chisel from a reputable UK brand costs less than lunch. The trap is buying an unbranded budget chisel where the heat treatment is uncertain: those chisels mushroom faster, lose their edge sooner, and are the ones most likely to shed fragments. Stay with the recognisable names.
| Tier | Price | Brands and models | Buy if... |
|---|---|---|---|
| Budget single (unguarded) | £3-8 | Faithfull FAI612 150x13mm from £2.58, Wickes own-brand 60CRV from £5.50, Roughneck 308RH 152x16mm £5.99 at Screwfix, Magnusson chrome vanadium 200mm £5.99 | You need a single chisel for occasional use. Unguarded chisels work fine if you have steady aim; they are lighter and easier to position in tight spots. |
| Mid-range single (guarded) | £10-17 | Magnusson guarded 300x30mm £10.99 at Screwfix, Wickes guarded 304x31mm £10.50, Sealey CC32G 250x19mm £11.07, Draper Expert 99170 250x19mm £14.76, Roughneck guarded 56313 305x25mm £16.99 at Screwfix | You want an overstrike guard for your hand and a lifetime or 25-year warranty. Roughneck and Draper Expert are the UK trade defaults. |
| 3-piece set | £9-22 | Stanley 6135K 3/8" 1/2" 5/8" £9.49 at Screwfix, Roughneck 863KF 200-250-300mm set £21.28 | You want multiple sizes for varied work. The Stanley set is the outright bargain; the Roughneck set gives you larger sizes and a canvas tool roll. |
| Chisel and bolster combo set | £26-32 | Wickes guarded 3-piece (brick chisel + point chisel + 1½" cold chisel) £26, Magnusson 5429V guarded set £26.99, Roughneck chisel and bolster 4-piece £31.99 at Toolstation | You don't own a bolster yet either. Better value than buying the two tools separately, and the guards make them safer for beginners. |
For a single-purchase recommendation covering an extension build: the Roughneck 56313 guarded cold chisel (305mm x 25mm, £17 at Screwfix) is the default. Drop-forged carbon steel, 25-year guarantee, comfort-grip overstrike guard, rated 4.7 stars across 28 reviews. It's the size that handles everything you'll realistically face on a kitchen extension and the guard means a missed strike bounces off rubber rather than knuckle.
If budget is the priority, the Magnusson 7510V chrome vanadium 350mm x 25mm at £8 (Screwfix) does the same job without the guard and with a lifetime guarantee. For a complete starter kit, the Roughneck 4-piece chisel and bolster set at £32 (Toolstation) gives you a cold chisel, bolster, electrician's chisel, and point chisel in one purchase and saves around ten pounds over buying them individually.
For a buy-British alternative, Footprint Tools in Sheffield manufacture cold chisels from single-piece forged carbon steel with a domed head designed to resist mushrooming. Priced from around £12 at Tooled-Up. Heritage tool, lifetime durability, but no practical advantage over a Roughneck for a homeowner project.
Guarded chisels cost £4 – £8 more than the unguarded equivalent but you will miss at least once during a project, and the guard is the difference between laughing it off and nursing a bruised knuckle for a week. For a first cold chisel, buy guarded. Once you know what you're doing, the choice is yours.
When to use something else
A cold chisel is the right tool for small, specific cutting and chopping jobs. For larger work, the economics change fast.
For splitting more than one or two bricks, reach for a bolster chisel. The wider blade spans the full brick face and produces a cleaner single-strike break. A cold chisel will split bricks, but only with scoring on all four faces first, and the narrower blade tends to produce angled breaks.
For more than a metre of mortar joint raking, a plugging chisel does the job better, or a diamond blade on an angle grinder does it several times faster (but kicks out silica dust that fills a garden). Hand chiselling is the right choice for period brickwork where power tools risk cosmetic damage; the grinder is the right choice for modern brick where speed matters and the joints will be repointed flush.
For cutting through concrete slabs or breaking floor sections, a cold chisel works for scoring small areas but you'll hate your life after ten minutes. An SDS drill with a chisel bit (from around £25-£45 per day from a hire shop) clears the same volume in a tenth of the time.
For cutting rebar longer than 10mm diameter, bolt croppers or a reciprocating saw with a metal-cutting blade are cleaner and faster. A cold chisel handles 6-10mm rebar fine. Beyond that, you're overworking the tool.
Where you'll need this
Cold chisels come out at several stages of any extension or renovation project:
- Foundations and footings - trimming protruding holding-down bolts and rebar offcuts flush before blockwork sits on them
- Walls and blockwork - cutting small fixings out of existing brickwork at the junction with the new build, chopping out mortar at tie-in points
- First-fix plumbing - clipping short sections of nail or fixing protruding into pipe runs
- Kitchen installation - removing broken tiles from existing walls before re-tiling, scraping off stubborn old tile adhesive
- Snagging checklist - cutting flush any protruding fixings or fastenings picked up during final walk-round
These jobs appear across every extension or renovation project, not just kitchen extensions. A cold chisel in the toolkit pays for itself the first time you need to cut a bolt flush or pop off a broken tile without a trip to the hire shop.
Common mistakes
Using a claw hammer. Already covered, but worth repeating. The claw hammer is the wrong tool mechanically, not just conventionally. Club hammer or ball peen.
Using a wood chisel on masonry or metal. The fine bevel folds on the first strike and the tool is ruined. A £15 wood chisel destroyed trying to do a £4 cold chisel's job.
Ignoring the mushroomed head until something flies off. The injury story repeats across forums because the check is easy to skip. Inspect before every session, dress the head before the rim flares.
Buying a bolster for metal work. Bolsters are softer steel and will blunt on the first strike against a nail or rebar. Narrow and hardened for metal, wide and softer for bricks.
Striking without eye protection. Safety glasses cost less than £5. Eye surgery doesn't. Metal fragments from a chisel head travel faster than you can blink.
Overheating the blade when sharpening. If you touch the cutting edge up on a grinder, cool it constantly in water. Blue steel is dead steel. The hardness gradient is what makes the tool work, and you cannot restore it without re-tempering in a forge.