By the Seat of My Chair

On Sunday, I got started on the seat for the Windsor Chair. I selected a 24″-wide poplar plank, 2″ thick. I needed every bit of the width, because there were some cracks on one side that I was just barely able to avoid and still get a 17″-wide seat blank. Unfortunately, this means that the grain won’t be centered, but at least I can avoid a glue-up.

After sawing out the blank with the jigsaw, I took it to the bench to be flattened. I started out with my jack plane with a cambered iron, working across the grain to take out the cup. The poplar planes easily across the grain.

Then I true it up with a short jointer (Stanley No. 6) working along the grain. Poplar is much tougher to plane with the grain than across.

Once one side is flat and true, I use a marking gauge to mark a consistent depth of 1-13/16″ thickness all around the blank.

Now, I just have to plane down to the gauge line, and I’ll have a true and consistently-thick seat blank. There are lots of complicated mortises to mark out and drill, so starting with a trued-up seat helps with the accuracy.

I start by using my pattern to establish the mortise locations. Each hole gets a nail, which will provide an unambiguous starting point for the auger bits.

Here’s where it gets…tricky. I have to mark out the sightlines for each and every mortise in the seat. The sightline is basically just the direction that each piece that joins the seat is angled. I can’t tell you how many erasers I chewed up trying to get these things right. Four legs, two posts, and seven spindles will all be mortised into this seat, and all of them have unique sightlines that must be precisely laid out. I brought the blank into the kitchen and enjoyed a cold brew while I puzzled it out. No use rushing this part.

Finally, it was time to start drilling. I used a 5/8″ auger bit for the legs. The bevel gauge must be set up perfectly parallel to the sightline. Every few turns, I stopped to make sure I was drilling at the proper angle.

You can see here that I’m a bit off. I need to raise the brace just a bit to get to the proper angle. Once you’re halfway through, the angle had better be right, because there’s not much you can do to correct it at that point. Any slight imperfections can be adjusted when I ream the holes.

Each pair of mortises requires a different angle. I used this angle gauge to set my bevel gauge, and the bevel gauge to align the brace and bit.

The legs and the posts get through-mortises, but the spindles only go 1″ deep. I used my burnisher with a bit of tape wrapped around it as a depth gauge. I aim for 1″ on the shallow side; since the holes are angled, the backside will be a bit deeper.

The work actually goes pretty quickly. Most people don’t realize how efficient a sharp auger bit is at boring through wood. Most of the time is spent setting the gauge and checking your progress. Soon, all of the mortises were drilled. Now the seat is ready to carve.