Tuesday, June 10, 2014

Forged carving tools and...... Sharp enough?

On Saturday some friends stopped by the house for a visit and one of their sons has been bitten by the wood carving bug.  The kid grabbed the nearest branch and got busy whittling, hard at work for nearly an hour, on making his perfect spoon. That was one of my first carving projects too, carving a spoon! Problem is, you need a knife with a properly shaped blade. Where does a kid get a good spoon carving knife?

Sunday morning I made these.

One is a curved, double edged carving knife, similar in shape to a yari-ganna (for him). The one on the bottom is a striking knife for marking layout lines (for me).

Both knives have cutting edges around 1-1/4" long. I used type O-F (Old-File) steel.

I might have to name this one "Nick".

This is the forth one of these knives that I have forged, of which two were immediately deemed too ugly to bear, and so ended up in the recycle bin. This one isn't terrible.

It has a pretty curve, but the sweep isn't dramatic enough. For carving spoons, I need to give the next knife a longer blade AND a more pronounced curve. I said the same after forging my last knife, but evidently this curve is etched in my brain, because this one turned out nearly identical to the last, haha!

The back of the blade is a bit hollow. The trick, for me at least, is getting the proper amount of curvature on the back, to support the cutting edge. The small land, in between the hollow and the edge, is what gives the knife stability. Too much flat and the knife will dive into the grain and will be hard to steer. Too little, and again, the knife will dive and be hard to steer. 

That weird, swoopy shaped, man-made aoto is coming in handy after all. The steel shows a beautiful lustre.

I actually like this stone! More later....

In use, the cut feels rather heavy. Part of that is due to poor sharpening....

...but mostly due to the bevel angle at the cutting edge.

The forged bevel angle measured at 32°.

My benchmark blade is a laminated steel Japanese craft knife.

This knife has the lightest cut of any knife that I have ever used. Nearly effortless cutting, moderate edge holding ability, and easy to sharpen, I assume that it is a simple high carbon/white paper steel.

The bevel angle of my craft knife/light saber measures at a far shallower 23°.

I gave the striking knife an extremely shallow bevel because I wanted to have a larger bevel surface to polish. This blade was clay coated prior to quenching, to temper the hardness of the steel. Mostly though, I was just trying to achieve a cool hamon effect (unsuccessfully, I might add).

It's there, just not very interesting. I like the clay quench, but need a lot more practice...... More knives!

This guy is a ridiculously low 13°!

I needed to put a 22° secondary bevel on this blade, both to stand up to use and to make a line thick enough to see.

My inspiration for spoon carving is Swedish carver Jogge Sundqvist.

Beautiful work.

Jogge Sundqvist spoon from Peter Follansbee ( humbly borrowed from his most excellent blog).

Speaking of sharpening....... How sharp is "sharp enough"?

Remember this guy? From the 5 part kanna restoration (Part 1), I have been using this kanna regularly, and though it showed early signs of edge wear, I figured that I would keep using it until it wouldn't cut any more. You need a VERY sharp edge to cut thin, but the ability to take a shaving of more practical thickness is a simple thing to achieve. That said, it's finally time to sharpen. 

This Red Cedar was pushing it.

You can see the shiny "Edge of Dullness", a bright line the full width of the blade.

 I would normally never let a blade get this dull, but this was a test, after all. This plane stayed functional for a LONG time, just not usable for the finest work. In some ways, a slightly dull blade cuts more effectively than a super sharp one. A sharp edge is temperamental, and will cause tear-out, just like a dull edge.

This still cuts pine, though. Cherry and walnut, too.

You can see how the shaving tears alternately, and goes from thick to thin. That would be caused by edge instability. The blade is alternately digging in, then popping out of the cut, signs of a VERY dull blade. Amazingly though, it will still cut!

Forging the occasional tool is a lot of fun, certainly more fun than buying something out of some catalog. Then again, for me the tools are more interesting than the projects. I need to work at the forge more.

The problem for me is that the laminated Japanese blades establish a VERY high standard, both in terms of edge durability, and the actual "sharpness" quotient. I find it very difficult to get a traditional western blade reeeeeeaaly sharp. There seems to be a point at around #2000-3000 grit where additional gains are negligible, and what little is gained is also quickly lost, generally after only a few cuts. I know that simple carbon steel can achieve and maintain a good edge, but the practice eludes me.

In my own forging, I want to work more at developing a good clay quench. Also to try a salt brine, to augment the basic oil or water quenches that I have been performing. And...... Swords. My daughter has requested a dragon sword, to be used for slaying knights! She wants it made with a nice cable Damascus, something with scales.

Someone's beautiful cable cable Damascus blade

What can I say? The kid has good taste in tools.

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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