Wood chisels are hand tools designed to trim wood and clear away the waste material from mortises and joints. They roots go all the way back to the late Stone Age, when crude rock and then flint was used for general purpose chiseling and cutting. Later, wooden handles were added.
Today’s chisel features a thin, beveled edge blade of alloy steel fixed to a smoothly curved handle made of hard plastic or boxwood. There are many kinds of wood chisels, including the firmer chisel, paring chisel, and mortise chisels.
To use a wood chisel for removing wood material in thin layers (paring), grasp the handle in one hand and use the thumb and forefinger of your other hand to hold the blade. Rest the hand holding the blade against the workbench or your work piece in order the guide and steady the blade. In this way, you are able to more accurately control the speed the chisel is driven as well as better align the cutting edge.
Mark off the waste area with a pencil on the work piece. Begin paring within the area to be removed, working toward the edge of your cutting area; if your beginning cut is made exactly on the edge of the removal area, then it is possible to go over the mark due to the bevel edge of the chisel, which you obviously do not want.
More Force Please
If you need to apply extra force to your paring stroke, then use your shoulder muscles. Most jobs only require hand pressure, but for extra hard woods, a mallet can be used to drive the chisel for maximum power. A Firmer chisel, which has a stout, rectangular shaped blade, is the type to use with a mallet. Only wood or soft-faced mallets should be used on chisels with wooden handles, plastic handle chisels can be driven with steel mallets or hammers.
Firmer chisels have blades around 4 inches long; the blade is beveled only at the cutting end. This chisel is best for general purpose woodworking use. There is also a variation called the beveled edge firmer chisel, or butt chisel, which has a blade with bevels on the top surface of the two sides. It is suitable only for lighter, more precision woodworking, as the all-around bevel makes the blade less rigid, and should not be driven with a mallet.
Former chisels usually come in blade widths of from 1/8 inch to ¾ inch, and special purpose ones can have blades up to 2 inches wide. A selection of chisels of ¼ inch, ½ and ¾ inch wide should be enough for most home workshop uses.
Another type of wood chisel is the paring chisel, which, is similar to the firmer, but has a longer blade, about 7 inches. It is used for cleaning out long grooves in wood. Common applications would be the grooves in wood shelf supports or stair stringers.
How to Use Mortise Chisels
The mortise chisel, also known as a joiner’s chisel, comes with a thick square shaped blade for clearing waste out; wide side edges help keep the chisel blade square in the mortise cut. The handle has a wide and slightly curved end and is designed to be hit with a mallet. Shock-absorbent leather collars are often fitted at the joint between the wooden handle and the blade.
A specialized variant called a lock mortise chisel is available with a longer blade, curved at the tip. Designed for cutting deep, blind recessed holes, the curved tip can be used as a lever to remove waste.
To use a mortise chisel, the width of the mortise is marked out with a mortise gauge that is set to the desired mortise width.
- Select a chisel with a blade width equal to one third of the size of the mortise’s width or leg, whichever is the smaller.
Now hold the chisel vertical in the middle of the marked off mortise with the blade’s non-bevel side facing towards you.
Hit the chisel handle end with a mallet to cut across the wood grain.
Gradually work back towards one end of the mortise, and stop about 1/8 inch from the marked line.
Start at the center of the mortise again, working your way to the other end this time
Repeat the process of cleaning out the mortise until the required depth is achieved.
Lastly, chop away the remaining 1/8 inch from each end of the mortise. Any excess wood on the sidewalls of the mortise should be cleaned away with the widest chisel available.
For a through mortise, clean away half the depth from one side of the work piece, then turn it over and clean the remaining half away, using the above steps.
Other Chisel Types
There are other types of more specialized chisel for particular jobs. The ripping chisel, used to split boards along the grain, looks somewhat like a crowbar, but with a wider and sharper chisel end.
The floor board chisel is an all-steel tool with a spatula shaped blade and octagonal handle. It is used to pry up tongue and groove floor boards to get access to electrical and other systems. A glazier’s chisel is used to remove old putty from window frames.
To keep your chisels in the best shape, always keep them sharpened. Blunt cutting edges will produce sloppy cuts, and more force will be required to drive them. Not only do you lose control of your cut, you also could injure yourself.
Storing your chisels vertically in a rack will prevent the cutting edges from becoming dulled or chipped by other tools. A light oiling every once in awhile will help prevent rusting on chisels that are infrequently used.