It is very important to adjust the angle of the edge according to the usage.
Below is guide given by Usui-san.
For very soft woods 24 ~ 26 degrees
This jig is so far the best sharpening jig I've ever come across. It is a bit expensive, but I believe it is worth every cent. The only minus point is that it can only sharpen plane blades but not the chisels.... If it could sharpen the chisels as well, I would've titled it without any hesitation "best jig in the world". But I guess Hatsuhiro didn't have the chisel in their mind, because Hatsuhiro is a plane blade maker! and the most famous one in Japan along with Nagahiro (not the one from Tokyo, but the one from Sanjyo).
In summary, I like this jig so much because,,,
1. The roller can be replaced very easily and the replacement piece is very cheap ($8).
This is a very important feature because I only use jigs for corase sharpening, and when the roller is unexchangeable, the lifespan of the jig itself is defined by the lifespan of the wheel which comes much earlier than the rest of the body.
2. The roller is not metal.
When the roller is metal, it digs the stone thereby concaving the center of the stone making the blade unpolished in the middle = need to fix the stone more often.
3. The blade is kept perpendicular to the longways of the stone.
4. Can set the angle of the blade easily without measuring with a rule. The dial at the end can easily and accurately set the desired angle.
5. The blade is secured easily without any tool, and will not come off at all cost. But just make sure you put a piece of thin wood or cardboard in between, to protect your precious baby from being scratched by the screw.
The one on the right is the one I used to use. I still use this to sharpen chisels. Good jig for super reasonable price. But there are couple of things it needs to be fixed for my usage.
1. When the roller gets ground to the point where the stopper on both sides keeping the roller in the center starts to scratch the stone, that will be the end of this jig's life. It is very cheap so it can be considered as a disposable jig, but even still there are couple of problems.
2. Depending on the shape of the plane blades' side, this jig doesn't hold it securely enough, so when you start to grind, the blade comes off, and it is quite dangerous. Yokoyama blades, which you all know as my most favorite blade, are the ones that comes off....
3. Every time you use it, you have to measure the length of the blade protruding from the jig with a rule in order to set the angle, and this is quite frustrating, because it has to be very accurate. Normally I'd have to reset it couple of times by acutally trying and see if it is set properly.
4. As I have mentioned above the metal roller digging the stone.
5. Last but not the least, as the roller gets ground, the correlation between the length of the protruding blade and the angle of the blade changes. So, in the beginning, 38cm means 28 degree, but towards the the end of this jigs life it is about 26 deg, and since the change is so gradual it happens without you noticing it.
The one from Hatsuhiro has solved all of these problems.