Chisels

Wood Chisel - hand tool with a wedge shaped cutting edge at the end of a metal blade, used for cutting or shaping wood.

Modern chisels have blades made of tool steel, and handles made from hardwood or synthetic materials. The blade is traditionally connected to the handle by either a tang or a socket.
A tang is a tapering square section at the end of the blade, that is forced into a round hole bored into the end of the handle. To prevent wooden handles splitting, a metal band (the 'ferrule') is attached around the end.
Socket chisels have a tapered socket forged on the end of the blade, into which the close fitting tapered end of the handle is inserted.
More recently there seems to be a move towards handles where the blade carries right through a synthetic handle, ending in a striking cap.

There are many types of wood chisel, but learning when and how to use the following four will allow you to achieve most anything:

• Bevel edged
  The bevels on the sides of the blade, allow the cutting edge to work into tight spots. Smaller chisel's  blades, which are not usually thick to begin with, are less strong as a result of the bevels, and so should not be used for heavy levering.
• Skew
  The cutting edge is prepared at an angle other than ninety degrees to the sides. Together with the bevel forming the cutting edge, this makes them 'handed'. Where the bevel edged chisel can't get, the skew probably can. In my woodwork, the obvious example is cleaning into the far corners of the pin board for a half- or full-blind dovetail joint. Both left and right handed skews are valuable when making these joints.
• Mortise
  Much thicker than the other chisels, and without bevels. They are made to be struck with force, and can be used to lever out waste. The deep, parallel sides, help to keep the chisel square in the cavity (the 'mortise') that they are designed to cut..
• Gouge
  Unlike the previous chisels, which all have a flat face, gouges have a cross section that forms part of a circle. They are used where rounded grooves or beads, or circular work of some description is required.

(In addition there are chisels specially made for carving wood, which require a whole section to themselves.)

Let's see some examples of chisels:

This is a budget price bevel edged chisel, with a synthetic handle and metal striking cap. Made from carbon steel, the blade takes a very sharp edge, but does dull more quickly than modern alloy tool steels.

High quality bevel edge socket chisel, with hickory handle. A2 steel holds it's edge well. This chisel can be safley tapped with a light hammer for chopping dovetail joints, etc.

A mortise chisel is much thicker, and has parallel sides. Mortise chisels are all designed to be struck quite heavily, and those with tangs will have ferrules.

Skew chisel, with the cutting edge ground at an angle other than ninety degrees to the side. This angle is not defined, simply chosen by the user to suit the majority of the work they use it for. Notice the lack of a ferrule, which indicates that this chisel must not be struck, but rather used to pare.

Carpenter's Gouge, with cutting edge at ninety degrees to the sides, but formed from a section of a hollow cylinder.
This gouge has a tang, and you can clearly see the ferrule which will prevent the handle from splitting.

And what I use when I chop with them:

7oz / 200g Hammer. I use this with all my bevel edge chisels for light chopping. The face is clean, and polished with 400grit wet/dry paper, which leaves a surface that won't mar the chisel handles.
I use a 10oz / 300g version for most of my mortise work.

Conventional Carpenter's Mallet. I no longer use this, as it feels very clumsy in comparison to a light metal hammer.

 In Use

Chisels are used either by pushing (known as 'paring'), hitting (known as 'chopping'). Special paring chisels exist, which have longer handles, and sometimes longer blades, but all chisels can be used to pare. A useful style of paring is slicing, which is where the cutting edge is pushed laterally across the point to be cut, with only slight forward pressure. Slicing reduces the effective cutting angle of the chisel, and can be used very effectively on softer wood, that would otherwise be crushed.As mentioned before, not all chisels can be struck, and therefore chopping is restricted to those that can.

The flat back of a chisel is like the sole of a plane, and it should be used to guide the cutting edge when paring or chopping a flat surface. In some cases this is impossible due to physical restrictions, and here it is acceptable to reference off the bevel.

By marking out chisel work with a knife, the chisel edge can be placed in the knife line to start it's work. This is vastly preferential to trying to align the edge with a pencil line.

Preperation and Maintenance

Honing paste on MDF

Chisel backs should be prepared perfectly flat, with the exception of gouges, which should be prepared with perfectly cylindrical backs. Flattening the back of a chisel is done by lapping on flat sandpaper and/or flat stones, until an even scratch pattern is observed over the whole surface. After which, the back should ideally be polished to a mirror finish. I achieve this by lapping on finer and finer abrasives or stones, and then with honing compound on a flat piece of MDF. Once flattened, the back shouldn't need any further work in the future.

Combination waterstone

Chisels are supplied with a general purpose bevel already ground on them. Should you specialise in either softwood or hardwood, then you may want to lower or raise the bevel angle respectively. Lower angles will work softwood better, whereas higher angles will survive working hardwood longer. Changing the bevel angle can be done on a grinder or on a flat abbrasive, producing either a hollow or flat bevel. I recommend a honing guide for all bevel work on flat abbrasives (sandpapers or stones) as the results are accurate and repeatable, and the process easy to pick up.

Fine India Stone and Honing oil

Honing to a super sharp edge will be a regular task, but one that only takes a few moments. It simply entails polishing a slightly higher bevel at the extreme tip if the cutting edge, and removing the wire edge that this produces. You can hone freehand by resting the bevel flat on a very fine abbrasive, lifting the back, or 'heel' by a fraction, and then working over the surface a little with the blade at the same angle. As soon as you can feel a slight wire edge (roughness felt when lightly stroking a finger off the cutting edge from the back of the blade), flip the chisel over, lay it flat on the abbrasive and pull back in the direction of the handle. If you've produced a mirror finish on the back, then you should remove the wire edge on the MDF board that you used, by pulling the edge back over the area of residual honing paste. The wire edge can sometimes bend over to the bevel side rather than rub off, so just check for that and repeat if necessary. The honed edge should easily slice through paper, or the hairs on the back of your hand.