To pare well, the chisel needs to have a flat face and a sharp edge. See the story at right on flattening for more about this. You can generally tell when your edge isn’t cutting the way it should when paring end grain. If the grain starts to collapse and bend over from the chisel pushing through, the chisel needs sharpening. I won’t go into a long diatribe on sharpening here, but suffice it to say that if your chisels are coming up dull, you either need to increase the frequency or quality of your sharpening.
At some time you’ll have to do some chopping with a bench chisel. A half-blind dovetail joint is a good example of how to use chopping to remove wood. Other uses for chopping are defining a hinge mortise, low relief carving and through-dovetails.
When chopping, you can use the same force you would use when mortising, just not as often. Bevel-edged bench chisels shouldn’t be used for mortising. They aren’t designed for this purpose. Mortise chisels have a steeper cutting angle ground on them: 30° compared to 25° for bench chisels. Their blades are thicker with square flat sides to stand up to a pounding. Bench chisels are thinner and beveled on the sides to get into tight spaces.
Most bench chisel chopping consists of light tapping of the chisel to define a cut line or remove a small amount of waste. Chopping is the most vigorous use that a bench chisel should see. Upon reading our reviews of 20 different bench chisels, only about half stood up to repeated medium/heavy chopping. If you plan on heavy use for your chisels, consult our review to get an idea of what to look for in a bench chisel.
Before beginning, make sure your work has a direct connection with the ground. That is, place the work directly over the leg of a bench or table. This imparts all the force of the blow directly into the cut and not into flexing your bench’s top.
I’m sure that back in the days when all mortising was done with manual labor, there were large muscular blokes all hammering and chopping away. This is certainly the woodworking equivalent of heavyweight boxing. The chisel and the wood both take an incredible pounding.
Mortising has one purpose: to make a square flat-sided hole in a piece of wood to receive a tenon. To that end, mortising chisels are the beefiest chisels you can buy. They have a steep grind (30°) and high flat sides to take a beating and guide the chisel while mortising. A bench chisel, with its thin profile, is likely to wander in your cut, ruining your mortise. Not to mention that if you hit a bench chisel as hard as you hit a mortising chisel, especially the small sizes like ?” and 3/8″, they might actually fracture. Also, repeated pounding of a bench chisel will either roll or collapse the cutting edge.
If you own only one mortising chisel, I recommend a 3/8″ tool. Tenons are typically half the thickness of your stock, and most stock is ?” thick. Make sure the mortising chisel you buy has a long handle because you’re going to hit it pretty hard. If the handle is too short, it’s your hand that will take the abuse.
Mortising has three parts. One, light tapping. This defines where the mortise will go and begins the mortise. Two, heavy pounding, which is what most of us think about when we talk about mortising. Three, paring. This is the only time you should use a bench chisel while mortising: to pare the sides of a mortise after chopping. PW
Jim Stuard is a former associate editor of Popular Woodworking.