WOOD CHISELS

A set of chisels will help your carpentry progress beyond the most basic. But you need to know some facts about choosing and using them.

There are half a dozen common types of woodworking chisel and the main thing that affects your choice is the design of the chisel’s blade. With all of them the actual cutting edge is at the end of the blade, but the blade profile varies. If strong and thick it will take a lot of bashing; if it is more delicate with sloping sides it is designed to reach into awkward corners. For some jobs you may find a chisel with an extra long blade handy and. For cutting curves, it’s best to use one with a curved cross section (called a gouge).

The handle material is also important. Traditionally, handles are made from wood. But although comfortable to hold. Wood is likely to split or mushroom out at the end if hit with a hammer, so a wooden mallet must be used instead. If the chisel is likely to be subjected to very heavy blows — when chopping out a housing or a mortise, for example — then a wooden handle must also be fairly chunky, or else have the end strengthened with a metal band. There are no such problems with plastic handles. You can hit these as hard as you like with a hammer or a mallet without fear of damaging them.

Having got the right chisel, look after it: don’t use it for opening paint cans and so on, and take care when working on old, used timber not to run into any nails or screws and nick the cutting edge. You should also make sure you sharpen it correctly. If you don’t, over the years the angle forming the cutting edge can become misshapen so that accurate work will almost be impossible to do — and a blunt chisel is useless.

CHISEL SAFETY

Chisels can be dangerous unless you follow a few safety rules. When working, never allow your hands or any other part of your body to get in front of the cutting edge, just in case you slip. When you have finished with the chisel, put it away. Don’t leave it lying about where it might cause an accident. To be doubly safe, fit it with a plastic blade guard — often supplied with the chisel when you buy.

Sharpening chisels

A new chisel isn’t ready for use. Although the end is angled at between 20° and 25’ (called the grinding bevel) to give what seems to be a cutting edge, this won’t cut for long — if at all. So, to provide a more durable edge, the very tip of the chisel has to be honed down to an angle between 30 and 35’.

To do this, you will need an oil stone — a rectangular block of abrasive material, normally carborundum. A combination oil stone is best. One face is a fine abrasive for normal sharpening; the other is coarser and is for drastically reshaping the grinding bevel if and when it gets damaged.

Before you begin sharpening, liberally cover the surface of the stone with oil which will carry away the metal removed from the chisel, preventing it from becoming embedded in the stone. A thin mineral oil is best.

You now simply hold the chisel bevel down, checking that it is at the correct angle, and work it back and forth over as much of the stone’s surface as possible — merely running it up and down will wear a groove in the stone’s surface. A useful additional tool is a honing guide – a sort of small trolley into which you lock the chisel to keep it at the correct angle on the stone.

After a while, run your finger down the chisel’s flat side and over the edge. If you feel a slight burr or ridge of metal the chisel is ready for the next stage. Place it flat side down on the stone and gently stroke away the burr. :.’.;;;;;

Mortise chisels

Specially designed to take the battering they get when cutting a mortise, these have a thick, almost square-sectioned blade, and either a very chunky handle (the sash mortise chisel) or one bound with a metal ring (the ‘registered’ pattern). Traditionally, a leather ‘shock absorber’ is included between the handle and the blade.

Bevel-edged chisels

These get their name from the blade’s sloping (bevelled) sides, and can cope with most jobs. They are particularly good at getting into corners and undercutting, but aren’t strong enough for very heavy chopping or levering. The most commonly available sizes — chisels are sized by blade width — are between 6mm (’/tin) and 38mm (1 Vain), in 3mm (Vain) steps.

Firmer chisels

A rectangular-sectioned blade makes the firmer chisel stronger and capable of quite heavy chopping-out operations. Unfortunately, it also makes it too unmanageable for cutting fiddly joints. Sizes are as for bevel-edged chisels.

Firmer bevel chisels offer the best of both worlds — they look like bevel-edge chisels but have thicker blades and are as strong as firmer chisels.

Paring chisels

Available in both firmer and bevel-edged patterns, these have a very long blade for cutting long housings and slots.

Gouges

Gouges are really just specialist chisels — the blade has a reshaped section. There are two types: scribing gouges have the bevel forming the cutting edge on the inside of the ‘C and are for cutting shallow grooves and the like; firmer gouges have the bevel on the outside and are for trimming curves.

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