How to sharpen Glestain and Misono Gyutou's?

[Zhu Chen]

A friend recently purchased both a 240 cm Glestain (hollow ground) and a 240 cm Misono UX-10.

She asked me how to sharpen them properly as both the face and the back bevels are distinctly different and are in no way equal.

Most of my knives are Masahiro, Western style MV stainless, which I treat and sharpen as a single bevel blade, in the traditional Japanese style.When I bought these Masahiro's in Japan I was told to maintain the factory configuration, and just sharpen the back flat, event though there was a barely discernible back bevel.

Both the Glestain and the Misono were both clearly ground as double beveled knives, but at different angles for face and back.

I was perplexed and was about to tell her to just treat the knives as a double bevel blade and sharpen both sides equally. Upon reconsideration, I hazzarded a guess to try a 6/4 or 7/3 front /back bevel sharpening ratio for each knife respectively. Ultimately we just decided to postpone the initial 'from the factory' tune up sharpening until we could get more certainty.

Can anyone help us out of this dilemma and offer some blade 'theory' on why these knives are ground this way and how to proceed? Is this simply a production factory variance or is it deliberate, and to what advantage? I would guess this would make it more difficult to detect the burr?

Colleagues in the business who use these knives apparently never noticed this disparity and just went ahead and sharpened both sides equally.

Your help would be much appreciated.

Zhu Chen
San Francisco

[RMgX]

Assymetric grinds are common on japanese western style knives, it is intentional and changing the bevels to 50/50 may change how the knife cuts.
To make sharpening easier mark each edge with a magic marker, depending on how the marker is removed you will see if you are holding the knife at to blunt an angle or to accute. You are probably not going to be able to recreate the bevel ratio exactly handsharpening but don't worry about that, just try to stick close. I think a search assymetric will give you some more tips.
Here is a discussion on assymetric bevels.
http://knifeforums.com/forums/showtopic.php?tid/784639/
Basically just sharpen each bevel it is allready at and you'll be fine.