Paring chisels have long blades of either firmer or bevel edged type. The long blade is so designed for reaching into awkward corners and for paring out long housings such as those used in bookcase and staircase construction. Because they have long blades, paring chisels should never be struck with a mallet or used with a lever action. This can cause the brittle metal to snap and may be dangerous.
Bevel edged and firmer chisels are available in a wide range of widths from lmm to 38mm. Initially, a set of 6mm, 12mm and 25mm chisels should be adequate for most requirements. Mortise chisels do not come in such a range of sizes and it is unlikely that anything other than 6mm, 8mm and 12mm mortises will ever be required. Buy paring chisels only when the need for a particular one arises.
Always select chisels that have smooth handles and make sure that the handles feel comfortable in your hand. Modern chisels usually have handles made of shockproof, splinter-proof plastic. Traditionally, chisel handles were made of boxwood or beech and although these are still obtainable, they are an expensive alternative to plastic. If you prefer wood, some chisels have handles made of beech which is much cheaper than boxwood but not as tough.
Always check that the blade is secure in the handle and that the blade and handle are in line. If the blade is wrongly aligned, the chisel will be incapable of producing good work. Check also that the blade is flat across its face—if it is not, it will be impossible to sharpen correctly.
Chisels are often supplied with plastic guards which fit over the end of the blade. If the chisels you choose do not come supplied with guards, it is well worth buying a set. Always replace the guard when you have finished using a chisel in order to protect the cutting edge, and to prevent accidents.
When working with a chisel, always keep both hands safely behind the cutting edge. Except for vertical paring, when the work is secured by your hand, hold the work firmly in a vice or cramp it to the work bench.
Trying to force a chisel leads to lack of control and a possible accident, so always use two or three thin cuts rather than one thick one.
Horizontal paring is a technique used when constructing joints—such as housing joints for supporting the ends of shelves and halving joints used in framework. These consist of slots across the grain of the wood and are normally made with a bevel edged chisel which is able to get into the corners of the joints.
When making such a joint, define the area of the slot by marking out / width lines on top of the wood, and width and depth lines on both sides. Make a saw cut, slightly to the waste side of each width line and cut down to the depth line. If the joint is particularly wide, extra saw cuts can be made in the waste to make chisel-ling-out easier.
Hold the wood securely in the vice so that it will not move as you work and make sure that it is horizontal. Hold the chisel in both hands, safely behind the cutting edge, with the elbow resting comfortably on the bench. This gives extra control over the chisel’s movement.
Start by chiselling out the waste adjacent to the sawn lines, making angled cuts to half way across the wood. Push the chisel firmly, holding it at a slight angle, keeping your arm horizontal and level with the work. When the cuts are half way across the joint, reverse the wood in the vice and complete the angled cuts from the other side.
Now turn the chisel over so that the bevel is facing downwards and remove the bulk of the remaining waste by slapping the handle of the chisel with the palm of your hand. Because the bevel side is facing down, the chisel blade works its way up to the surface and no levering action is needed to clear the waste. Again chisel only half way across the joint, then turn the wood around and work from the other side with the bevel side of the chisel facing upwards once more. If you chisel right across the joint, the wood will break and splinter out on the other side.
When most of the waste has been removed, work the chisel across the joint, keeping it absolutely fiat across the bottom, to shave off the last fibres of wood. Finally, hold the chisel vertically in one hand and work the blade into the corners to clean them out and sever any remaining fibres.
Vertical paring is necessary when you wish to round off a corner or to make a curve in a piece of wood.
Hold the wood on a bench hook, to protect the surface of the work bench, and support the other end, if necessary, with a timber offcut of the same height as the hook. Hold the chisel upright in both hands with the thumb of the upper hand over the top of the handle to give control and downward force. The lower hand ‘steadies the work and also grips the blade of the chisel between the index finger and the knuckles of the other fingers. Keep your head over the work as you pare away the wood.
Mark the required curve on the wood and cut off the corner, to an angle of about 45°, with a tenon saw. Holding the chisel as described, pare off the corners left by the saw cut. Keep paring off the corners, taking off thin slivers of wood not more than 1mm thick. If you take off thicker cuts than this, the extra effort involved may cause you to lose control of the chisel.
Work as closely in to the curve line as possible, then finish off by smoothing with a file.
Cutting a mortise
A mortise is a rectangular slot cut into a piece of wood into which a tongue—called a tenon—from another piece of wood is fixed. The mortise and tenon make a strong joint which is used to form T-shapes in frames. The mortise should always be made with a mortise chisel—the width of the chisel’s blade determines the width of the mortise.
To mark out a mortise accurately you need a mortise gauge. Using a chisel of the exact width of the planned mortise, set the gauge to the chisel blade and mark out the width lines on the wood. With a try square as a guide, draw the two setting-out lines which determine the length of the mortise.
When cutting a mortise, the wood should be held securely on a solid part of the bench rather than cramped in the vice: as the chisel is struck with a mallet, it would dislodge the wood from a vice. Use a G cramp (C clamp) to hold the wood in position and protect the top with a timber offcut. Make sure that the tail of the cramp is beneath the work or injury may result. Drive the chisel into the wood with a mallet—never use a hammer to hit a chisel as this may damage the handle, making the chisel uncomfortable and unsafe to use.
Start by driving the chisel into the mortise to dislodge a deep wedge of waste. Use three separate strokes of the chisel to remove the wedge, making it equal on both sides. Keep your body behind, and in line with, the work. Work, with a series of small chops, from the centre towards one of the setting out lines keeping the chisel in the same vertical plane at all times.
Stop at the line, turn the chisel round and approach the other setting out line with a further series of chops.
Clear out the waste and dislodge another wedge in the centre to the depth of the finished mortise. A band of tape wrapped around the chisel blade to the required depth makes a good depth indicator. Chop up to both setting out lines, again to the required depth.
If you are cutting a mortise to go right through the wood, chop to half way from one side then turn the wood over and work from the other side. Never chisel all the way through to the other side or the wood will split.
No matter how correct your technique or how expensive your chisels, you cannot produce good work with a blunt chisel. You should always check that cutting edges are sharp before use and hone them if necessary.
Chisels are sharpened on oilstones which are made in three grades of grit—coarse, medium and fine—and come in two sizes—150mm x 25mm x 25mm and 200mm x 50mm x 25mm. Coarse grade stones remove large particles of steel and are therefore needed only when a cutting edge is chipped or badly damaged. Medium stones are used for normal sharpening of the blade and for dealing with small nicks in the cutting edge. Fine stones hone the blade to a sharp edge. For sharpening on oilstones, you also need oil—not to act as a lubricant, but to carry away particles of metal before they become embedded in the stone.
Chisels have two angles to their cutting edge: the ground angle of 25° and the honed angle of 30°. The ground angle is formed on a powered grindstone and only occasionally needs regrinding.
To hone a chisel, apply a liberal amount of oil to the stone and hold the blade at an angle of about 30° against the stone. Keep the blade square to the stone and rub it in a figure of eight motion to distribute wear evenly over the stone. When a burr—known as wire edge—begins to form on the flat side of the blade, turn the chisel over, Rub the flat side across the stone to remove the wire edge, keeping the blade perfectly flat upon the stone. If you raise the chisel handle, however slightly, the flat side of the blade becomes bevelled and the chisel cannot be sharpened to a fine edge.
When the wire edge has been removed, return to the bevelled side of the blade. Rub each side of the blade in turn, using less and less pressure, until a razor sharp edge is produced.