Chisel

• 1. Introduction

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  A chisel is a hand tool defined by one small detail: a wedge-shaped cutting edge on the end of its blade. That wedge is the whole idea. Force it into wood, stone, or metal, and the material gives way. The force can come from a hand pushing, a mallet, or a hammer. In industrial settings it can come from a hydraulic ram or a falling weight, a kind of trip hammer that drives the blade home. From that single shape grows a sprawling family of tools, each shaped for a different material and a different job. How does one wedge become a slick large enough for shipbuilding and an engraving tool tapped with the lightest of hammers? Why does a cutting edge meant for cold steel look so different from one meant for soft pine? And what is a gouge, the curved cousin that turns a flat blade into something that scoops?

• 2. The Woodworker's Many Blades

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  Roughing out a pattern in wood begins with a large chisel and works down to smaller tools to finish the detail. That progression, big tool first, fine tool last, defines how woodcarvers approach a shape. The firmer chisel carries a thick rectangular cross section, which makes it strong enough for tougher and heavier work. The bevel edge chisel does the opposite job, slipping into acute angles thanks to its bevelled edges. For deeper cuts there is the mortise chisel, a thick rigid blade with a straight cutting edge and deep, slightly tapered sides for making mortises and similar joints; registered and sash mortice chisels are common types.

  A paring chisel solves the problem of reach. Its long blade is ideal for cleaning grooves and getting into tight spaces. The skew chisel takes a different approach, with a 60 degree cutting angle for trimming and finishing across the grain on a wood lathe. The dovetail chisel exists for a single joint, distinguished by the thickness of its body and the angle of its edges, both shaped to ease access into the joint. A butt chisel stays short, with beveled sides and a straight edge for creating joints, while carving chisels handle intricate designs with many cutting edge forms, including gouge, skew, parting, straight, paring, and V-groove.

  The corner chisel resembles a punch and carries an L-shaped cutting edge, made to clean out square holes, mortises, and corners with 90 degree angles. A flooring chisel cuts and lifts flooring materials for removal and repair, suited to tongue-and-groove flooring. The framing chisel pairs with a mallet and runs longer than a butt chisel, with a slightly flexible blade. Stranger still is the drawer lock chisel, an all-metal tool with two angled blades for tight spaces, such as cutting out the space to fit a desk drawer lock. The largest of all is the slick, used in timber frame construction and wooden shipbuilding.

• 3. Cutting On The Lathe

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  Woodturners need leverage, so their gouges and chisels carry longer handles. The wood spins on a lathe, and the tool fights a constant downward force from the turning piece. A longer handle gives the turner the leverage to counteract that tendency. The angle and method of sharpening also differ from ordinary woodworking tools, a quiet sign that the spinning workpiece changes the rules of how an edge must be ground.

• 4. Steel Against Steel

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  A cold chisel is made of tempered steel and cuts cold metals, meaning no heating torches or forges are involved. It removes waste metal when a very smooth finish is not required, or when a hacksaw, file, bench shears, or power tool cannot easily do the work. Its cutting edge sits at a less acute angle than a woodworking chisel, trading sharpness for strength at the edge. These tools span a wide range, from fine engraving tools tapped with very light hammers to massive ones driven with sledgehammers. They are forged to shape, then hardened and tempered to a blue colour at the cutting edge. The head is chamfered to slow the mushroom shape that hammering creates, and left soft so it does not splinter through brittle fracture under hammer blows.

  The flat chisel is the most widely known type, used to cut bars and rods, reduce surfaces, and cut sheet metal too thick or difficult for tin snips. The cross cut chisel handles grooves and slots, its blade narrowing behind the cutting edge to provide clearance. A round nose chisel cuts the semi-circular grooves that form oil ways in bearings. The diamond point chisel cleans out corners and difficult places, and is also useful for pulling over centre punch marks placed wrongly for drilling. Most cold chisels are steel, but a few are made from beryllium copper for situations that require non-sparking tools. In Repoussé and chasing, cold chisels do much of the work of fabricating bronze and aluminium sculptures.

  A hot chisel cuts metal that has been heated in a forge until it softens. The hotcut hardy is one type, set in an anvil hardy hole with its cutting edge facing up. The hot workpiece is placed over the chisel and struck with a hammer, which drives the piece into the blade so it can be snapped off with a pair of tongs. When the piece being cut is particularly large, the hotcut hardy is often paired with a top fuller type of hotcut.

• 5. Stone, Brick, And Mortar

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  Stone chisels carve or cut stone, bricks, and concrete slabs. To cut rather than carve a brick, a brick bolster is used; its wide flat blade is tapped along the cut line to make a groove, then struck hard in the centre to crack the stone. Sculptors reach for a spoon chisel, which is bent and carries the bevel on both sides. Because stone resists, these chisels are often hit with club hammers, a heavier type of hammer that adds force to every blow.

  Masonry chisels are heavy, with a relatively dull head that wedges and breaks rather than cuts. They often serve as demolition tools, mounted on a hammer drill, a jackhammer, or hammered manually with a hammer of three pounds or more. Their connections are usually SDS, SDS-MAX, or 1-1/8 inch Hex. The family includes moil or point chisels, flat chisels, asphalt cutters, carbide bushing tools, the clay spade, flexible chisels, and the tamper. A plugging chisel has a tapered edge for cleaning hardened mortar from joints, held in one hand and struck with a hammer. The direction of the taper in the blade decides whether the chisel cuts deep or runs shallow along the joint.

• 6. Punching Through Leather

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  In leather work, a chisel punches holes rather than cutting away material. It carries between one and seven tines, possibly more, placed carefully along the line where holes are wanted. The worker strikes the top with a hammer until the tines pierce the leather, then withdraws them. Through the resulting holes the leather worker stitches the piece together, a job where the chisel prepares the path rather than finishing the work itself.

• 7. The Curved Cousin

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  A gouge is a chisel whose blade is curved or angled in cross-section rather than flat. The modern version is hafted inline, so blade and handle share the same long axis. When the bevel sits on the outer surface of the curve, it is an outcannel gouge; otherwise it is an incannel gouge. Gouges with angled rather than curved blades are often called V-gouges or vee-parting tools. Their geometry follows a semi-standardized numbering system that varies by manufacturer and country of origin.

  The sweep number expresses the part of a circle defined by the curve of the blade. It usually runs from #1, meaning flat, up to #9, a semi-circle, with specialized gouges at higher numbers like the U-shaped #11 and a v-tool or parting tool that may sit even higher, such as #41. A second number gives the distance from one edge of the blade to the other, the chord of the circle section the edge defines. Together the two numbers describe the cutting edge, written as something like a #7-20mm. Some manufacturers supply charts that show their sweeps graphically.

  Blade variations push the gouge into places a straight blade cannot reach. A crank-neck gouge offsets the blade from the handle by a small distance to allow working flat to a surface. A spoon-bent gouge curves along its length to work in a hollow that a straight blade cannot enter. A fishtail gouge stays very narrow for most of its length and broadens near the working edge, fitting into tight spaces. The cutting shape of a gouge can also be held in an adze, roughly the shape of a modern-day mattock. A violin luthier uses gouges to carve the violin, a cabinetmaker runs flutes or pares curves with them, and an artist may cut bits from a sheet of linoleum in a linocut. Gouges were found in a number of historic Bronze Age hoards in Great Britain, proof that this curved edge has been shaping material for thousands of years.