Saturday, September 13, 2014

Using the "Point of a sword" knife

Yesterday was just one of those days.....

I seem to be direly lacking in practice, woodworking wise. Things seem to be going quite well and I'm in the groove, but then you offer up the piece at the final fitting...... Too short! Cut a new one....... Even better, but again, too short! It's not quite the old joke "I cut it, and I cut it, but it's still too short!", but it feels pretty damn close.

Working larger pieces (in this case I'm rebuilding our back deck) while trying to maintain close tolerances, is an art unto it's own. I guess that there are two approaches that could be taken.

You can:

  1. Cut every piece flat, straight, and true. Every piece is reduced to a common dimension. 
  2. " Cut to fit ". Each piece is an entity and construction proceeds in a linear fashion. Fit each piece to the previous one.

I love and admire " Flat, straight, and true ", but this way of building just doesn't work for ME. This is like my imagined ideal. Layout is perfect and exact, joints are simple(er) to cut, and things come out as planned. For this to work, all components must be oversize, to end at the desired dimension, so there often must be huge amounts of waste. It's also a lot of work reducing the stock, so power tools are most often used. This is " Set it and forget it ".

" Cut to fit " is my reality. Each piece is different and must be sculpted to fit the way that you want it. NOTHING is flat, straight or true, so scribing (as opposed to measuring) is the rule. This can work well, but you need the proper mindset. A minimum of material is wasted, but you get tired of walking back and forth, and few corners can be cut. Trying to save time often results in errors further down the road.

I try for a hybrid approach. For small stuff like a cabinet, this works well. You make the case perfectly, then scribe fit it for installation. For bigger stuff it gets more difficult. Boats are all scribe work, while houses are somewhere in the middle. Our house would list heavily towards the scribe end of things.

We are taught to think in terms of "Flat, straight, and true" (FST), and when things don't work out as planned, we get frustrated and confused. When you do enough if this work (say carpentry) you learn a multitude of little tricks that help you accommodate the inevitable inconsistencies. You assume FST, then work the reality. This works great for machines, OK for groups of people, but makes me (the individual) a bit nuts.

It is a mindset thing. I measure, then cut, always anticipating the next step. My mind is centered on a whole, looking at the goal as a finished project, in this case a deck. My attention and energies are diffuse and thinly spread, because I only have so much to invest at any given time. The usual outcome is a finished product that looks acceptable, and a perfect job is one that gets comments like "And you made that by hand? Really?!! It's as good as that one I saw at the store!". My problem is that I am concentrating on being "done", and therefore not fully present. This makes me feel tired. Big projects get delayed, because you are already anticipating how much work something will be, and how tired you will be when it is finished.

Yesterday's work was me falling into the hybrid FST trap. I cut things close, leaving a margin for adjustment, and thinking ahead. Thinking efficiently. Measure, cut, fit, and finish. Offer it up, often in pairs. A very minor thing (like refining a joint to a hair thin line), can cause two pieces to be essentially too short. Because you ALWAYS start with the longest piece, you can reuse the miscut pieces somewhere else, at least. My time (and the energy invested) are gone, but at least I get more practice this way.

If I look at each step as an individual project, I find that I do dramatically better work. I GAIN energy as the project progresses, rather than feel relief at being finished. This change in mindset is such a simple thing, and it alters EVERYTHING. Instead of thinking about the most efficient way of doing something, I try to do this ONE thing well. My tools have never been sharper, and my cuts have never been straighter.

That said.........

The "Point of a sword" knife has leaped up into my top 10 list of "Tools that I didn't know that I needed ". When "Good enough" isn't, and my joints need a little bit of's a little bit like an eraser for wood.

Separate the joint, only enough for access. I can use it one handed, but it's big enough to use with two.

Combined with my favorite kerfing saw.

Best friends forever!

The knife excels at endgrain. The knife coming to a point means that it cuts with a shearing action. The point can access tight areas like corners.

I formed the point on this knife at a 90° angled tip, but a lower angle would be useful for detailed work. I plan on making another style that has a "sharper" point, and has beveled sides like a dovetail chisel (shinogi-nomi)

Here's an easy one. The tongue on this finger joint is crowned slightly (probably from "crowding" the saw and driving it to hard).

Not perfect, but better. If each thing is better than before, after a while they get pretty darn good.

I thought that this knife would maybe be as useful as a paring chisel, but really more of a curiosity. Interesting.........but how often will you really use it, you know? To the contrary, I am finding it to be one of my most used tools. Two handed, you can take very thin,  controlled, shearing cuts. One hand is fixed and provides the anchor/pivot point, while the other gives drive. Or, you can just stab it at the area that needs adjusting, and the wood curls out of the way. The knife cuts with a unique plunge cutting action that is unlike any other tool that I have. A joinery shiv, haha!

The pointed shape of the tip seems to provide balance to the cut, and the flat back helps to keep the cut planar. There is occasionally a tendency for the blade to dive, so perhaps an ultra-flat back isn't necessary. I'm not sure, and am withholding judgment.

This knife was forged from a small piece of old Nicholson file (O-F) steel, forge welded to a larger piece of mild steel (something that my daughter and I dug out of the muck at the marina). Clay slip, water quench,  3 temper cycles at 325°F for 1 hour. The O-F steel is proving very interesting. Very easy to sharpen, it feels very different on the stones than even, say, YSS white steel #2 (a simple 1.00%-1.20% high carbon steel). It sharpens like a soft chisel, but has shown no edge degradation and hasn't needed honing yet, after 4 days of fiddling with Port Orford cedar. Now that I think of it, when sharpening, it feels similar to how carbide sharpened with diamond feels. Carbide is VERY easy to sharpen, if you use diamond.

The knife cuts lightly, but feels toothy somehow (even though I polished the edge using my finest stones), and the edge LOOKS great under the microscope. Weird. I'm curious to see how the edge chips (as it inevitably will).

There is a guy named Murray Carter that makes Japanese style knives professionally. He has an edge sharpness test that he calls the "3 finger" test. Maybe it's 4 fingers, I can't remember, but the gist of it, is that if you touch the edge of a knife using 3 or 4 fingers simultaneously, and your hair kind of stands up in alarm...... That's sharp. It sounds goofy, but it does kind of work and it certainly is an interesting metric. This knife still feels that way, after 4 days of use. I wonder how hard it is? I would guess around Rc60-62, but people terms to overshoot their numbers, so.... It is harder than my hardest file, anyways. What I REALLY want to know is how TOUGH it is.

These are from the tool kit of a Japanese pro.

I wonder why he has 4 sizes? The second from the left (24mm?) looks like it sees a bit more use.

Eye aspire.

Clean. Nice. Candy.

1 comment:

Like all of us, I am figuring this out as I go, so when you see something that is incorrect or flat out wrong (and you will!), let me know. This is a learning process. Real people and names, please. Constructive comments and questions are very welcome, but hate speak/politics are not! Life (get one!) is too short.

Thanks, Jason