How do I use a chisel properly?

A chisel is the most precise cutting tool most people own and the one most often used badly, because it arrives blunt and nobody sharpens it. Everything else about technique is secondary to that.

Safety

Step by step

1. Sharpen it before first use.New chisels are ground, not sharpened. Work through a coarse and then a fine stone, then strop. It should shave hair from your forearm. This is not an optional refinement — it is the difference between the tool working and not.
2. Flatten the back as well.A chisel cuts on the meeting of two surfaces. The back must be dead flat for the first few centimetres, done once when the chisel is new and never again. Sharpening the bevel against an unflattened back achieves nothing.
3. Clamp the work.Always. A chisel that slips off a piece being held by hand goes into the hand holding it. This is the most common serious injury with the tool.
4. Understand bevel up and bevel down.Bevel down levers waste out and cuts a curve — used for chopping out the bulk. Bevel up, flat against the surface, pares flat — used for the finish. Choosing the wrong one is why holes come out dished or torn.
5. Score the line first.Knife the boundary of the cut rather than pencilling it. The knife line severs the fibres so the chisel cannot tear beyond it, and it gives the chisel a physical wall to register against.
6. Work from the waste side.Chop and pare from within the waste towards the line, never from outside it. The last cut lands in the knife line, which is why the line is knifed rather than drawn.
7. Take thin cuts.A millimetre or two at a time. A chisel driven deep splits along the grain and takes more than you intended, and the split does not stop at the line.
8. Read the grain direction.Cut with the grain rising away from the edge, not diving into it. Cutting against the grain tears out chunks below the surface. If it starts tearing, work from the other direction.
9. Use a mallet for chopping, hands for paring.Chopping out waste is mallet work. Paring to a line is done with hand pressure and body weight only, which gives the control that a mallet cannot.
10. Pare with two hands and your body.One hand guiding the blade close to the edge, the other pushing from the handle, with your shoulder behind it. Controlled pressure rather than a shove.
11. Keep it sharp as you work.A few passes on a strop every ten minutes rather than a full sharpening session at the end. The moment it stops slicing cleanly, stop and strop.
12. Protect the edge.Blade guards, or a rack. A chisel rolling loose in a drawer against other steel is a chisel that will need regrinding.
13. Never use it as a screwdriver or a lever.It chips the edge and can snap the blade. Chisels are for cutting, and a chipped edge takes a long time to grind out.

Tips

• A honing guide costs very little and makes sharpening repeatable rather than a skill to acquire. It is the single best purchase for anyone new to chisels.
• Sharpen before you think you need to. Fifteen seconds on a strop is faster than the five extra minutes a blunt chisel adds to a cut.
• A cheap chisel sharpened properly outperforms an expensive one that is not.

Common mistakes

• Using a chisel as it came from the shop — New chisels are ground rather than sharpened. The tool cannot do its job until the back is flat and the bevel is honed, and forcing a blunt one is how it slips.
• Chopping deep in one go — The wedge action splits along the grain and the split runs past your line. Thin repeated cuts remove the same material with control.

If it doesn't work

Questions people ask