Every once in awhile I get hit with questions about using an EdgePro correctly to sharpen asymmetrical knives (like all Japanese knives). Most everyone seems to be confused about this subject so I thought I'd take a minute to bring to light a few things that apply to the EP specifically as well as free hand sharpening of these knives.
Since we know that all Japanese knives are asymmetrical we can assume that each side will likely be sharpened as such and if we look we see this is true more often than not.
When we sharpen a knife we will usually follow the edge bevel ratios that have been defined by the making of the entire blade. We see 100/0 (single bevel knives) & 90/10, 80/20, 70/30, & 60/40 for double bevel (western styled) knives.
If we follow the edge bevel ratios that have been defined by the maker then we may, or may not, need to adjust the angle between the side of the blade and the stone's face IF we're freehanding, however, if we're using an EdgePro then we ALWAYS have to adjust the angle of the stone arm for each side (different on one side versus the other) to account for the asymmetry worked into the entire blade. This occurs with the use of the EdgePro because the knife is being placed (fixed) onto the table of the device and the edge is not centered in the middle of the blade (spine) as it is on symmetrical knives such as the device was designed to be used on.
Key points for both free hand and EdgePro sharpening is to adjust the angle for what EACH side of EACH knife requires EACH time you sharpen it. Do not look for repeat-ability as something you want - you don't - you want to always start sharpening at the top of the edge bevel and work your way down to the cutting edge. One side may be 15 deg and the other other 8deg - so what - adjust your angle of attack to allow you to start at the top of the edge bevel (on EACH side independently) and work your way down and you'll always be OK. If this means that we have to adjust our EdgePro arm 25 times during one session (that's adjusting for stone thickness deviations as well as angle changes from side to side) then that's what we should be doing.
The thing that I always want people to understand is that we should be using our minds & eyes to look at what we're doing and make adjustments as necessary. Selecting an angle of attack and blindly going at it isn't very good sharpening at all. Even the newest sharpener who opens up his eyes will make better edges than the seasoned sharpener going at it with a fixed repeatable angle.
Since we know that all Japanese knives are asymmetrical we can assume that each side will likely be sharpened as such and if we look we see this is true more often than not.
When we sharpen a knife we will usually follow the edge bevel ratios that have been defined by the making of the entire blade. We see 100/0 (single bevel knives) & 90/10, 80/20, 70/30, & 60/40 for double bevel (western styled) knives.
If we follow the edge bevel ratios that have been defined by the maker then we may, or may not, need to adjust the angle between the side of the blade and the stone's face IF we're freehanding, however, if we're using an EdgePro then we ALWAYS have to adjust the angle of the stone arm for each side (different on one side versus the other) to account for the asymmetry worked into the entire blade. This occurs with the use of the EdgePro because the knife is being placed (fixed) onto the table of the device and the edge is not centered in the middle of the blade (spine) as it is on symmetrical knives such as the device was designed to be used on.
Key points for both free hand and EdgePro sharpening is to adjust the angle for what EACH side of EACH knife requires EACH time you sharpen it. Do not look for repeat-ability as something you want - you don't - you want to always start sharpening at the top of the edge bevel and work your way down to the cutting edge. One side may be 15 deg and the other other 8deg - so what - adjust your angle of attack to allow you to start at the top of the edge bevel (on EACH side independently) and work your way down and you'll always be OK. If this means that we have to adjust our EdgePro arm 25 times during one session (that's adjusting for stone thickness deviations as well as angle changes from side to side) then that's what we should be doing.
The thing that I always want people to understand is that we should be using our minds & eyes to look at what we're doing and make adjustments as necessary. Selecting an angle of attack and blindly going at it isn't very good sharpening at all. Even the newest sharpener who opens up his eyes will make better edges than the seasoned sharpener going at it with a fixed repeatable angle.