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Measuring sharpening angles.

Sat Jul 06, 2013 2:03 pm

Hi Guys,

Here are several ideas for measuring angles, from the most NASA ish, to the most stone age ish.

The Angle Cube is really cool and small so it works well on a knife blade.
http://www.chefknivestogo.com/anglecube.html

However, if you don't have one, cant afford one, or are just really lazy and cant press "add to cart", here is another method, although somewhat less practical given it requires your phone. ( Yea, I know, that made no sense )

Image

Its an app called oddly enough, Level.

If you are anti technology, a bit of paper folded into a triangle = 45 degrees. If you fold that triangle over itself, it = 22.5. Fold it again, 11.2. Fold it again, 5.6. Fold it again, and you are way stronger than me.

Happy measuring :D

Re: Measuring sharpening angles.

Sat Jul 06, 2013 3:00 pm

When freehanding the angle cube is a pain to use because the face has to be turned to the left or right of you, they don't show you that. You can hold and look at an angle to get an idea of what that angle looks like. Nearly impossible to see while actually sharpening to see how consistent you hold your angle. I can see how it would be great with the Edge Pro though.

Re: Measuring sharpening angles.

Sat Jul 06, 2013 3:46 pm

Lol, am a free hand sharpener, I just eyeball it. Never had anyone complain yet. (Knock on wood)

Re: Measuring sharpening angles.

Sat Jul 06, 2013 3:53 pm

I continue to be tempted by the Angle Cube. Perhaps one day, with a little mirror. How fast does it respond? A freehand stroke is under a second somewhere, but at least it might show slow "drift" in freehand angles.

At least for me, better than the folding-paper approach is the ruler method -- measure the width of the blade ("width") and then the height of the center of the spine off the stone ("spine") gives the angle, within about a degree for the angles we are talking about and without a fancy calculator, as

angle ~ ( spine / width ) x 60°

So:
  • 1 in 4 ~ 15°
  • 1 in 5 ~ 12°
  • 1 in 6 ~ 10°
  • 1 in 10 ~ 6°

An example -- 48 mm high gyuto, 1-in-6 angle gives 48/6 = 8 mm to raise the center of the spine off the stone for about a 10° half-angle.

Even if the angle isn't exact, it is repeatable, which is what is usually important. I generally don't care if I am sharpening to exactly 12° but I do care that, for example, last time I sharpened the edge didn't last as long as I wanted, so I want a little bigger angle this time.

Re: Measuring sharpening angles.

Sat Jul 06, 2013 3:55 pm

kalaeb wrote:Lol, am a free hand sharpener, I just eyeball it. Never had anyone complain yet. (Knock on wood)

I just eyeball it now too, but it was helpful to know what 15 or 20* angle looked like when you first started to learn.

I like your method Jeff, going to try it out.

Re: Measuring sharpening angles.

Sat Jul 06, 2013 11:03 pm

I freehand and have cut a few wine corks with an inclination corresponding to different sharpening angles, just for reference.

Re: Measuring sharpening angles.

Sun Jul 07, 2013 5:04 am

Put the angle cube on the knife and 'set it' to the angle you want. Then slowly do a stroke or two maintaining that angle to see how consistent you are. It is good training.

BUT when you move, the angle will jump all over the place. Don't expect to use it in actual sharpening just to train your muscle memory (proprioceptive feedback). The circuitry is that of an accelerometer where the angle offset is used (subtracting an ac coupled signal) to yield a voltage proportional to the angular offset. Because of this any acceleration will make the numbers reported totally useless.

Alternatively you can set the angle of the stone and use the knife in a horizontal plane to increase your precision when freehanding.

---
Ken
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