One day in the 1990s, a few of us at Popular Woodworking Magazine were talking to Troy Sexton – one of our contributors – about table saw blades. We asked Troy what blades he liked.
“Thin kerf,” he said. “Always thin kerf.”
One of the other editors scoffed a bit. “Why would you need a thin-kerf blade on your 5hp table saw?”
Troy said: “They save wood. The difference between a 1/8”-wide blade and a 3/32” blade makes all the difference at times.”
I couldn’t agree more. Today I was roughing out the parts for two new chairs from some precious material: bog oak that is between 2,000 and 4,000 years old. I would never buy this material for myself. It’s too rare and unpredictable. But local furniture maker Andy Brownell had some chair-sized scraps from a dining table commission. He generously let me pick through the scraps for pieces that had dead-straight grain and few splits.
I’ve worked with bog oak before. So I was skeptical that I could make a chair from it. But I also trust Andy’s judgment when it comes to wood. So I gathered up enough material to make a chair and headed home.
I started cutting into the oak on Friday and was absolutely amazed. The bog oak I had used years before was lightweight and brash (brittle). That oak was filled with tension, so pieces warped like crazy. And some chisel handles I turned from it broke in short order.
This stuff from Andy is different. It is heavy, stable and incredibly strong. I made some 3/4” x 3/4” sticks and hit them with a sledgehammer (the “sledgehammer test” in “The Stick Chair Book”). The sticks just bounced, as I would expect from straight oak that was cut last year.
Why the difference between this bog oak and the brittle stuff from a decade ago? I can’t say exactly. I am sure that one difference is in how quickly the two oaks grew. The bog oak from 10 years ago was very slow-growth stuff. So there were tons of pores. This new bog oak grew incredibly fast. Some of the growth rings were 1/4” to 3/8” apart. Fast-growing oak is much stronger than slow-growing oak.
The difference might also have been how the material was dried, handled and processed. I have no idea how the bog oak from a decade ago had been dried. But the new stuff came from M. Bohlke Lumber north of Cincinnati. Bohlke specializes in cutting and drying incredible and difficult woods. The Bohlke facility is nothing short of astonishing.
In any case, because of a thin-kerf table saw blade and lots of planning, I was able to squeeze parts for two chairs from the lumber I’d hoped to get one from. I did this by carefully resawing the curved parts from lumber that was 2-1/8” thick in the rough. Even with modern oak from a reputable kiln, resawing can be tricky. Tension in the wood can make the boards warp immediately when sawn through their thickness. And if the wood isn’t completely dry, the boards can curl later on.
This stuff was as stable as resawing MDF.
Even though everything has been going well so far, I know that trouble lies ahead. All this bog oak is from one tree, which is great. But there is an amazing amount of color variance along the widths of the boards. The wood goes from a charcoal-amber to an almost pitch black. Juggling all those colors means I have to finish the parts before assembly to ensure my chairs don’t look like calico quilts.
Luckily, I have about three times as many sticks as I need for two chairs. Also, when building chairs you don’t need all the wood to match exactly. The wood in the horizontal plane (seat and arms) can be a little different than the stuff in the vertical plane (sticks). And the undercarriage (legs and stretchers) can be another shade without looking wrong. Light hits a chair differently than it hits a cabinet.
With all these variables with the material, I decided that the chairs’ designs shouldn’t be an additional one. The two chairs I am building are designs I have built many times, so there won’t be any surprises when it comes to angles or how the chairs’ forms will look.
But I am sure there will be other difficulties ahead I can’t foresee.
— Christopher Schwarz