Part 3 – Butterfly Joinery – Prepping the Legs
After I mostly finished the table top (more on that later), I needed to start thinking about the under structure for our heart pine farmhouse table. The legs and aprons would have to be super sturdy in order to support the top, which is easily a hundred pounds of lumber. For this purpose, I selected the heaviest beam from the lumber that Uncle Bob and Aunt Gail gave to us in December. This 12-foot-long 4×6 beam was a monster, and was quite awkward to carry into the crawl space for cutting.
I used a hand saw to cut the beam into four 29-inch-long legs. Combined with the width of the table top, this will set our eating surface 30.25 inches off of the ground, which is a pretty standard height. The tables I looked at online ranged from 29-31 inches tall, so I shot for somewhere in the middle. As you can see in the photo above, I used a corner edge to keep the saw cutting at a 90 degree angle so that the cuts were straight. Even so, the legs were ever so slightly wonky, so I had to go back over the tops and bottoms with a belt sander to level them out. Using hand tools opens the door to greater inaccuracies for an amateur like me, but I really enjoy using them.
After I had cut the legs, I sanded them down using a combination of belt sander and random orbit sander with grits ranging from 32 to 220. This is the same technique I used when sanding the legs to our 7-foot-tall shelf.
During the sanding process, a long crack in one of the legs became more pronounced and noticeable. Since this beam was cut from almost the very center of the tree, one corner of the beam shows a quarter circle of rings that are very small. This center section of tree had started to separate from the rest of the beam, and the crack ran almost halfway down this particular leg. In order to repair this crack and stop it from spreading, I used two techniques: wood glue and butterfly joinery.
The wood glueing is pretty self-explanatory I think. Squeeze some glue into the crack and clamp the crap out of it with as many clamps as you’ve got. Check. The butterfly joinery part is a little more fun and intricate. It involves cutting a butterfly shaped piece of hardwood and inserting into a butterfly shaped hole across the crack you’re repairing. In order to cut the butterflies, I used a template I picked up from Highland Woodworking supply in the Virginia Highlands (that’s a neighborhood in Atlanta). As you can see in the photo above, I’ve got everything clamped down firmly so that the router’s inlay bit won’t move things around as it cuts.
The inlay bit does a great job of cutting out perfect little butterflies from the 1/4″ heart pine I had Don Shomaker cut for me in his shop. Note the direction of the wood grain in the butterfly. It’s important that the grain runs across the crack you’re repairing. If the wood grain runs in the same direction as the crack, the forces pulling the crack apart can easily break your butterfly apart.
The inlay bit I used to cut the butterflies is also perfectly capable of cutting out the butterfly shaped holes in the legs, but I wanted to do this by hand. My final product wasn’t perfect, but I’m doing this woodworking stuff as much for relaxation and skill building as I am for the finished product. Hand tools give a certain level of pure satisfaction. You can see in the photo above that I cut a light groove in the leg’s surface around the pre-cut butterfly. I then used a very sharp chisel to remove the waste wood.
You can see the crack running straight through the center of the butterfly shaped hole in the leg. The idea is that the crack won’t be able to spread outwards because of the shape of the butterfly. It’s really a very simple, yet ingenious concept.
After the hole was cut, I added some glue to all sides of the butterfly and a little into the hole and hammered it in with a rubber mallet. It’s not a perfect fit, but it’s not too bad for my first one cut by hand. I actually cut two more for the same leg and each one was a little better than the last.
Above, you can see the butterfly after sanding. Below, you can see all three of the butterflies in the leg. Thanks for reading. -Robby