BASIC CHISEL TECHNIQUE

Whatever chisel work you're planning, the first step is to secure the workpiece. For light work, such as paring, you can just clamp the workpiece in your bench vise. But if you're doing heavier work (especially rigorous work like chopping mortises), clamp the workpiece to the top of the bench. For the best support, try to position it directly over (or as close as possible to) the legs of the workbench. This helps dampen vibration and prevents the workpiece from bowing under heavy blows.

Support blockFor chisel work where you're paring the full width of the workpiece, or through the work-piece, you should always insert a support block under it. A support block not only protects your workbench from certain damage, but also helps prevent tear-out by solidly supporting the wood fibers where the chisel exits the work.

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Slicing cutAlthough I've always considered a slicing cut to be one of the more basic chisel techniques, I rarely see it being used. This specialized form of the blade grip should be in everyone's bag of tricks. I use two forms of this cut. With one, I grip the blade almost like a pencil and use it vertically to lightly pare away wood. With the other form, I grip the blade with one hand and use the other to form a fulcrum. This way, I can pivot the chisel into the workpiece, such as when slicing a dowel flush with a surface. Either way, it's a great grip.

TRIMMING TENONS

A common paring task for a chisel is trimming or cleaning tenons for a mortise-and-tenon, a slip joint, or a stub-tenon-and-groove joint. There are a couple of critical areas of the tenon that usually need attention: the cheeks and the shoulders.

CheeksThe first thing I do when fitting a mortise-and-tenon joint is to check the fit of the tenon in the mortise. Since it's always better to have a tenon that's too big (if it's too small, you'll need to recut it), the tenon will often require a little paring to fit snugly. I use a wide chisel for this and an underhand grip to lightly pare away the excess. Start at one end and use the lip created by the chisel to reference the next cut. Take light cuts and check the fit often.

ShoulderOnce the tenon fits into the mortise, all that's left is to make sure the joint fits snugly together with no gaps. Even when you're careful cutting a tenon, it's easy to end up with a "stepped" shoulder. To clean up the shoulders, start by taking light, horizontal paring strokes to clean out the intersection of the cheek and shoulder. A long time ago I learned the value of "undercutting" the shoulders. That is, instead of making a 90-degree cut, I just start inside the shoulder (around 1/16") and tilt the chisel up slightly. This undercuts the shoulder and virtually eliminates any fitting problems.

CLEANING OUT MORTISES

The other half of a mortise-and-tenon joint, the mortise, often requires some "tweaking" after it has been cut. If I've cut the mortises by hand, I usually only need to tweak the tenons for a good fit. If you use a machine, you may need to do a little or a lot of work. If the mortises are router-cut, they'll likely only need the corners squared. If you drilled them out, you've got considerable work to do.

SidesTo clean up the sides of a mortise, choose a sharp chisel that's fairly wide. Take care to keep the chisel vertical (a guide block clamped to the workpiece helps), and take light cuts. Skewing the chisel also produces a cleaner shearing cut.

EndsMortise ends often require paring, either to size the mortise correctly or to square up corners. Although a lot of folks advise using a chisel that's the same width as the mortise for this, I've had better luck with one that's slightly narrower. This way the chisel doesn't get jammed between the sides, and you don't have to rock it to get it out. Rocking like that can enlarge the mortise,

creating a sloppy fit.

BottomThe bottom of a mortise is a difficult area to clean up, since access is limited by the sides and ends. The best way I've found to do this is to use a chisel with the bevel up and take light, scooping cuts. Avoid the temptation of using the top edge of the mortise end as a fulcrum point for the chisel: You'll only crush this edge and end up with a weaker joint.

TRIMMING GROOVES

In addition to cleaning up mortises and tenons, I routinely use a chisel to fine-tune grooves, rabbets, dadoes, and other joints.

Paring sidesOne of the more common paring tasks is removing just a bit of material from the side of a groove or other joint. Whenever possible, I use the blade grip for this and take a slicing cut. This offers a couple of advantages over the more conventional vertical paring stroke. First, skewing the blade creates a cleaner shearing cut. Also, it makes it easy to slide the flat back of the chisel along the side of the groove or dado as a steady starting point. This way you start with a very light cut and ease into the waste.

Ends of the grooveWhether a groove is cut by hand or by machine, there's often a tendency for the final few inches of the groove to be the incorrect depth. This can be caused by letting up on the workpiece as it passes over a spinning bit or blade, or by easing pressure near the end of a cut made by hand. To correct the depth, I use an underhand grip and pare away the waste with a series of light cuts.

Cleaning up the bottomCleaning up the bottom of a groove is fairly straightforward. Here again, flip the chisel so the bevel is down, and run it along the bottom. Inverting the bevel like this prevents it from catching and digging into the groove.