Tuesday, May 22, 2018

Curtis Buchanan Sackback Day 3

Here's an extract of pine relieved from the groove delineating the spindle deck of the seat from the dished part receiving future, hopefully grateful, asses.
Today we started in earnest upon boring holes into this gorgeous pine. Next to the scent of fresh white oak shavings, this pine tingles my spine with delight. I can't tell which i like better, it's usually what's not been on the scene for an hour or two.

Now, I am not the guy to delve into the geometry that's going on here, but i will try to share a few parts. Hardest part about drilling a hole is going in at the angle you intended. this includes 90deg, of course! But none of the angles here are anywhere close to that figure. So the layout lines designed into this piece are meant to assist you with visual cues on how to guide your drill bit at the correct orientation. A concept of "resultant angle" helps reduce this into solving the problem as simple as is possible. just google it.

probably the most unusual tool in this kit is the reamer, which is the wooden tapered implement seen in the field below having a metal cutting edge (harvested from a hole saw i gather?) that floats in a kerf along the axis of rotation. It's a 3 degree angle off axis, and you can use this to figure out what angle to set your tapered bores at, with really good accuracy. None of us students had used this method before so it took a lot of checking, and rechecking of our bevel guages and trepidatious steps into the pine. What's great is that curtis has designed this process to allow for correction if you don't nail an angle right. the taper boring tools allow for course corrections if you're a bit off. YOu will apply cutting pressure towards the direction that you want to aim for. with tapers this is possible. It would not be possible with straight tennons.

Once the leg and major arm rail holes were bored, we were ready to do some preliminary shaping of the seat. We start with a very unusual instrument called the adze. It's the tool you see on the left of the seat piece curved along the throw and the striking plane. It cleaves large chips from the pine in one throw, once you get the hang of it. it's obvious you have to be careful with this tool. know where your supporting hand is and where your knees are. But honestly, you dont really apply any force to the cut. when done right, the mass of the adze head does exactly what you want, and it chips out the waste.

for pine, it's kind of overkill because it's such a soft wood. Regardless, it saves work for Act II "The Scorp"

THis was my first time using a scorp. it's essentially a drawkife that has been bent into a "U" shape. I love this tool despite not having been able to really do good work with it, i watched Curtis relieve his seat using it with a grace and sweeping action that is breathtaking. A scorp will teach you rather strictly about grain direction and how to slice through the grain to maintain an angle of incidence that produces clean cuts. Too high and you don't cut anything. Too low and you start to dive into the grain.
We then do what i think is the most important cuts to define the leading edge of the seat. You dive down and then sweep up in a curve that is lobed towards the outside and points gradually to the topmost point (I think this is also called the "pummel"). what better instrument to deliver this shape than the draw knife! use it bevel down for agility and angle the blade for a skew cut. go big on this one.
I'm not quite there yet but close. I need to shave to make the leading edge of either side of the pummel a little less blunt. That's important for aesthetic reasons but also ergonomic ones as having a blunt nose here i think would be uncomfortable on the hamstrings...

that's all today. tomorrow will be new territory in the travisher and who knows what.

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