Hand Chopping Mortises

It's not that hard to hand chop mortises. My first efforts were pretty crude, but by now, I can chop a reasonably precise mortise without destroying a lot of wood. There are several ways to approach the task. Any way you approach it, you need to first mark the mortise. I suggest a mortising gauge which has two marking pins or wheels. This will definitely save you a lot of inaccuracies in marking the sides. I have been measuring the top and bottom mark, but anytime you measure, you stand a chance of introducing error. If possible, use the same marking gauge for laying out the top of your mortise that you used for laying out the corresponding dimension of your tenon.

The next step is to get the wood out. Here's where the choices come in. One approach is to drill out as much as possible and then clean up with a chisel. I've done this in the picture below. Note the use of squares to help keep the drill vertical. Also, the bench pup from Lee Valley helps keep the workpiece steady on the workbench. This method is relatively easy, but I find it hard to keep the drill holes exactly in line and I find the chisel slips around as I try to clean out the wood, resulting in a not-so-precise mortise. This method also gives me a chance to use my Buck Rogers brace, so that's one point in it's favor.


The next approach is to take a mortise chisel and lay it in the scribe marks and start whaling away. Start in the middle and work toward one end, then turn the chisel around and work to the other end. You will find that you are able to drive deeper and deeper, the further from your initial cut, because you are creating more room to push the excess fibers into as you drive them out of the way. Thus, the bottom of your mortise has a distinct hump in the middle which must be cleaned out. Also, I have severely damaged the wood using this technique. The wood can shear along the grain and blow out the top of the piece if you are working with small parts. My opinion is that this technique is best used for rough construction.

Lastly, here is my preferred method. Drill one hole near the middle of the mortise, registered against one mortise cheek mark, and keep this mark as the reference mark throughout. Then, take the mortise chisel and carefully chop toward one end. The hole allows the fibers to easily move out of the way. Turn the chisel around and chop to the other end. Keep the chisel square to the scribe marks and registered against the reference mark. A little paring and cleaning of the bottom and the mortise is done.

My next article will discuss paring and bottoming the mortise to the required depth.