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EdgePro - Use It Correctly

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Dave Martell

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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.
 

Dave Martell

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PS - The EdgePro will not sharpen single bevel knives correctly. It is possible to make them sharp but not to follow the grind and angle changes along the length properly.
 

Justin0505

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Great post!
I think that a lack of understanding of the things you mentioned is 1 of the main reasons the people don't get good results an end up blaming the tools to vs their own technique.

This all gets back to the old carpentry saying of "measure twice; cut once. "

Along the same lines of "paying attention to what you're doing when sharpening" I would add that it's important to check your progress as your grind down the bevel and towards the edge so that you know when you are actually on the edge. Theb once there, it's important to maintain the same consistency and feel/check that you are creating an even bur along the entire edge.

It all sounds kinda basic/common sense, and but it was something that I had to
concentrate on when I first started on the edgepro as ignoring it will get you a wavy over/under-grind mess.
 

Dave Martell

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That's so true too Justin. It's like, "OK, time to move on down the edge now."

That same thing can also be said for free handing too though, too often we spend the most time in the easiest section right in front of the heel and no time on the curve and tip.
 

EdipisReks

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That same thing can also be said for free handing too though, too often we spend the most time in the easiest section right in front of the heel and no time on the curve and tip.
that tendency is exactly why i do my edge testing mostly at the tip and curve of the knife. i can be pretty sure that if those parts are sharp enough that the heel probably is too. ;)
 

Sarge

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That's so true too Justin. It's like, "OK, time to move on down the edge now."

That same thing can also be said for free handing too though, too often we spend the most time in the easiest section right in front of the heel and no time on the curve and tip.
Funny I have the opposite problem I need to remind myself to make sure I do a thorough job on that last 1/4 of the knife at the heel. I use the front 1/3 of the knife for most of my cutting and the heel rarely gets a real workout though so it does make sense that area needs a bit more work each time.
 

heirkb

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I'm a bit confused. Wouldn't this mean your angle gets lower every time you sharpen? That's what would happen if you aim to hit the top of your previous bevel, right?
 

Eamon Burke

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I think he is talking exclusively about setting the bevel and getting it right. Of course you shouldn't try to wear down the shoulder on a 10k stone.

I have to say, I focused on setting a new bevel on a few knives with this in mind today. It's basically like adding a little skill(holding it steady) and patience for results, and you don't have to wear out the knife, and you have like no wire edge hoopla. It's kept to a minimum--as soon as the big burr is raised, even a little bit, the bevel behind it is fully built up and in place already.
 

heirkb

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So then every time you set a new bevel, you're lowering the angle? Wouldn't this be a problem for knives sharpened at a steepness close to the max they can take? You wouldn't want to lower the angle more on an 8 degree bevel, for example, right? Sorry if I'm missing something, I'm just curious.
 

Eamon Burke

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You will always be working the shoulder first because the knife gets progressively thicker up to the spine. Or else you end up with a knife that has an edge with the same angle numbers, but is .5mm thick at .5mm from the edge.
 

Dave Martell

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You will always be working the shoulder first because the knife gets progressively thicker up to the spine.

Eamon has that right and that's the thing to understand, you're only keeping the thickness in check by starting at the shoulder and working down, you're not making the edge too thin unless you really try to.
 

Chef Niloc

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I think he is talking exclusively about setting the bevel and getting it right. Of course you shouldn't try to wear down the shoulder on a 10k stone.

I have to say, I focused on setting a new bevel on a few knives with this in mind today. It's basically like adding a little skill(holding it steady) and patience for results, and you don't have to wear out the knife, and you have like no wire edge hoopla. It's kept to a minimum--as soon as the big burr is raised, even a little bit, the bevel behind it is fully built up and in place already.
that wire edge hoopla will always come back to haunt you
 

Chef Niloc

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PS - The EdgePro will not sharpen single bevel knives correctly. It is possible to make them sharp but not to follow the grind and angle changes along the length properly.
What about the other edgepro like sharpeners? Like the gizmo, will that sharpen single bevel knives correctly?
 

Cadillac J

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as soon as the big burr is raised, even a little bit, the bevel behind it is fully built up and in place already.
I'm a bit confused, as this is how I've always sharpened and set bevels.

What were you doing before you focused on this in your recent sharpenings? Were you getting a burr way prematurely before your bevel was ready or something?

Maybe it was in your wording and I'm not understanding what you meant.
 

Eamon Burke

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No, I was just paying extra attention to why it works. The main reason I have done that is because it is consistent and helps ensure you are removing fatigued steel, as well as helping to thin the old shoulder. But I never really thought about how it relates directly to burr formation and good the end result is.

Sorry if I am being unclear, I'm on a goodly amount of sudafed and ibuprofen.
 

Benuser

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On another forum a novice asked recently how to sharpen a Hiromoto AS with an EdgePro. He got the advice - by someone who said to be a pro sharpener - to give it a symmetric edge...At least we are better off.
 

stevenStefano

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Just so I can understand this in my own head. Dave, you are saying that if sharpening an asymmetric edge say 70/30, the smaller bevel (30) should be sharpened at a lower angle than the bigger side so that you are actually hitting the edge and not just the shoulder?
 

Benuser

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As we met in the Hiromoto case please allow me to give my answer. If I'm wrong I expect Dave to correct. I would sharpen the large, convex, right, kanji bevel eventually on 11-12 degree, and the flat, small straight bevel on the left at some 14-15 degree. And this humble proposal caused a lot of fuss. Of course you should start with some thinning behind the edge, therefore the 8 degree is a reasonable starting point.
 

Benuser

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Oh, the 70 percent is related to the right side. The 30 percent is the small left bevel with a more obtuse angle.
 

Dave Martell

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What gets left out of these conversations is that it's not just the edge bevel that asymmetric - it's the entire blade that is asymmetric - the edge simply mimics the blade grind. If this isn't factored into the thought process then I can see why people advise to just make the edge symmetrical (50/50) because they likely figure why not but if we do consider that the blade is ground asymmetrical then we realize that there is more to the picture than meets the eye and that we shouldn't be ignoring this fact.

I advise three things....

1. Follow what the maker has already done with regards to angles/ratios. This will keep the knife cutting straight.

2. If the knife has been fudged with by an "expert" then do your best to recreate the blade's asymmetry in the edge bevel as much as possible. If you do this you'll find that you'll get pretty close to getting the knife to not wedge and cut straight. This is how I fix stuff all the time.

3. Always start sharpening at the top of the bevel and work your way down to the cutting edge. This keeps the edge thin and keeps the ratio in balance.


Those simple rules keep everything good in the world. :)
 
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Dave Martell

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On another forum a novice asked recently how to sharpen a Hiromoto AS with an EdgePro. He got the advice - by someone who said to be a pro sharpener - to give it a symmetric edge...At least we are better off.

That's the typical EP user answer there OR they say to take more off of one side than the other OR to count strokes, etc. That's all phooey because what needs to be done is to look at the knife and do what it needs. If one side needs adjusting to the stone arm to make the correct angle (that's different from the other side) then that's what you do. Changing angles, ratios, or simply doing a 50/50 symmetric edge is playing games and will provide a bad result. You might not realize what you've done from one or two sharpening jobs but I'd bet the bank that it won't stay hidden as an issue forever. The user will eventually feel either twisting and/or wedging and then look for the reason.
 

Benuser

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I think this approach will work as well with European blades which are never exactly symmetric either. Often one side convex, the other more or less flat, even if the edge is well- centered. Strictly applying the same number of strokes will in the end lead to poor geometry as well.
 

mateo

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It's threads like this that make me realize I'm such a bloody noob to sharpening... I love the info though.
 

heirkb

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Dave, if we are sharpening freehand and assuming that the original bevels are gone, how can you tell what angle ratios the knife will need? Do you somehow eyeball the asymmetry and then sharpen based on a guess of what the asymmetry of the entire blade is?

Also, does anyone have a link to a good thread on asymmetry? Should the angles change or is it about the number of strokes per side? Sorry to revive what I'm sure is a very old question.
 

Dave Martell

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Dave, if we are sharpening freehand and assuming that the original bevels are gone, how can you tell what angle ratios the knife will need? Do you somehow eyeball the asymmetry and then sharpen based on a guess of what the asymmetry of the entire blade is?
There's two easy ways to see the asymmetry in these knives.

1. Holding the knife by the handle, flip it to have it's edge facing up - tip away, then look down the choil while holding it up to a light. A really thin 60/40 might not be so obvious here but most others show up pretty clearly.

2. Lay a straight edge (like an engineer's square) on the side of the knife (from spine to edge direction) making sure that it contacts the spine, now note the space/gap between the lower portion of the blade - then do the same to the opposite side and compare the difference seen.



Also, does anyone have a link to a good thread on asymmetry?
There's a ton of old asymmetry threads over at KF that you can dig up but not all info is good. If you find any of them in Keeping Sharp you should skip those, some of the ITK ones might be OK.


Should the angles change or is it about the number of strokes per side?
For the free hander the angles often don't need to be changed but sometimes they do, this is one of those things that just needs to be looked at and decided on case by case.

Counting strokes is a gimmick. I'm happy for someone who is happy with doing this but IMO it's not a general rule type of thing that I'd like to see people follow as it's got too many reasons why it might not work which to me means probably won't work. Again, I think that simply opening our eyes and looking at what we're doing gets the job done great.
 

Eamon Burke

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For the free hander the angles often don't need to be changed but sometimes they do, this is one of those things that just needs to be looked at and decided on case by case.
:plus1:
That is the great thing about freehanding, not a lot of jiggery(pun intended). Unless you are sharpening someone else's knives, then it gets fun. Then you sharpen knives from a restaurant. Then you lose faith in humanity.
 

Dave Martell

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This is a bad drawing for sure but maybe it'll help in understanding the difference between asymmetric and symmetric edges.



assymetry.JPG
 

Cadillac J

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Sometimes I don't trust the makers stock bevels, especially the ones that look like they took 2 seconds to put on via a belt without disregard or any thought involved...so then I do what Dave mentioned and look at the natural asymmetry of the blade itself to help determine my estimates.
 

heirkb

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So based on the picture Dave posted, it seems that one side is just sharpened more than the other. Is that right? That's what I meant when I said number of strokes. I should have said material removed (at the same angle).
 
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