Using the Edge Pro sharpener on curved blades

[jalapeno]

I've spent some time fishing through Youtube videos on the Edge Pro, and I'm looking specifically to see different techniques used for handling curves in smallish blades (~2.5-3") that are beyond just mild curves.

I get reasonable results with larger and only mildly curved blades like kitchen knives, but for the smaller and more curvy blades, I need work on technique.


Unfortunately all the videos I've come across where people are doing actual sharpening are using mild curves where they are able to keep the knife in one place for the entire process.


Does anyone know of any edge pro (or similar) videos showing sharpening of more curved blades especially around the tip?


If there aren't any such videos, what I'm struggling with is keeping the blade steady as I round the curve, and then hitting that exactly again after I flip sides of the knife or change stones.


For example, I just got an Ontario RAT 2, and its curve near the tip (while not extreme) seems too large to just hold the knife in one position while sharpening it. My edge just doesn't look uniform as I curl the knife during the tip portion, and flip back and forth between sides. I can't seem to hold the knife exactly the same on subsequent passes and it results in sort of a "lumpy" looking edge. If it matters, I am left-handed.


Any advice on technique for such a knife, or maybe DIY clamping or aligning jigs, would be appreciated.

(PS if it matters I have the pro model and I got it around 10 years ago, for maintaining kitchen knives. I don't think it has changed since then but not positive)

 

[cbwx34]

The knife you mentioned (Ontario Rat 2) is not too large to hold in one position. I would mark the edge with a Sharpie, and set the knife based on the tip area (in other words, don't try to "center" the knife on the blade table). You'll probably find it'll work best with the belly/tip area just at the side edge of the blade table.

I think Ben (Edge Pro) video on using the machine is one of the best at showing how to do this...

[video=youtube;p8p5DteXBcE]https://www.youtube.com/watch?v=p8p5DteXBcE[/video]

... (it's worth watching a couple of times... he gives a lot of hints throughout).

If you do decide that you want to move the knife as you sharpen, the key to avoiding the issue you're having (the edge looking "lumpy") is to just practice moving the knife smoothly across the blade table as you sharpen the edge. Try and set the knife (again referring to the video above) so that you can move it in a continuous motion, and not in sections. Again, referring to the above video... notice on the large knife how he sets the table stop based on the belly tip area, so that he can move it smoothly back and forth. The other problem (I had anyway) is just learning to relax a bit, and not try and hold the knife tightly against the blade table as I moved it across... made it harder to move it smoothly. Ben shows it in this video (around the 5 min. mark, but the whole thing is worth watching)...

[video=youtube;CY6DJ0PQxyA]https://www.youtube.com/watch?v=CY6DJ0PQxyA[/video]

... learning to relax, especially the grip on the knife, made the job go smoother for me.

Hope that helps... I know they're EP instructional videos, and you may have seen them already, but I think Ben gives the best tips in them, if you pay attention to the details he provides.

 

[jalapeno]

Thanks cbwx34. This is hard to describe in words so I used a photo of the RAT-2 to make a graphic outline:

In the graphics below, the width of the edge pro base (light orange) and the alignment piece (green) are to scale relative to the knife so that the positions are fairly accurate.

I tried to keep roughly the same edge overhang distance at each step, and only used the stone on the part of the edge that was roughly parallel to the base (shown with a small red rectangle in each step).

So I have to keep the blade spine against the corner of the green alignment piece at all times, keep the blade flat against the table, and pull and turn the knife counterclockwise for each new incremental step, like this progression:

But I think what you're saying (refer to the figure below) is that if I sort of "split the difference" in the edge from tip to heel, where the center of the curve ("A" in the graphic) is my alignment focal point (i.e. that is the only part of the edge that is parallel to the edge pro table's front edge), while also having enough tip overhang ("B") and heel overhang ("C") to clear the stones, and keep "D" as small as possible to be on the flat of the blade, and then set the alignment plate at "E" after all those things are accounted for.

Then I just hold the knife in this one position and hit the entire edge with the stone? Do I have that right?

Alignment points of blade relative to edge pro:

Then I do a mirror image of all that, to get the other side of the blade, like this?

 

[cbwx34]

But I think what you're saying (refer to the figure below) is that if I sort of "split the difference" in the edge from tip to heel, where the center of the curve ("A" in the graphic) is my alignment focal point (i.e. that is the only part of the edge that is parallel to the edge pro table's front edge), while also having enough tip overhang ("B") and heel overhang ("C") to clear the stones, and keep "D" as small as possible to be on the flat of the blade, and then set the alignment plate at "E" after all those things are accounted for.

Then I just hold the knife in this one position and hit the entire edge with the stone? Do I have that right?

Alignment points of blade relative to edge pro:

Then I do a mirror image of all that, to get the other side of the blade, like this?

First, may I just say, very nice diagramming. :thumbup:

I'll primarily address the part I quoted here. You don't want to "split the difference" (that's what I said earlier, you don't want to "center" the blade), and you don't need to find "A". All you need to do is set the blade so that you can cover the whole edge. Mark the entire edge with a Sharpie, set the angle you want to sharpen at, and make a pass along the entire blade with a fine stone. You can make adjustments of the curved area by pivoting the blade in/out a bit, and/or moving the blade stop. (Easier than it sounds). BTW, once you find the spot, you may also want to document the distance where the blade stop is set.

There's not a significant angle change along this length... that's why finding "centers" isn't needed.

Also, keep in mind that on many knives, the belly/tip area is sharpened at a higher angle from the factory, so that everything "matches". So the initial sharpening on a guided device may take a bit to have everything match the angle.

Hope that helps.

 

[jalapeno]

I'm still confused. Maybe my choice of words ("split the difference") wasn't a good one and confuses things. When you say, "All you need to do is set the blade so that you can cover the whole edge," wouldn't the knife position in the portion of my drawings that you quoted accomplish that?

Or would the knife position in one of the sequence of knife movements in the first part of my post with drawings be closer to what you're talking about?

 

[cbwx34]

I'm still confused. Maybe my choice of words ("split the difference") wasn't a good one and confuses things. When you say, "All you need to do is set the blade so that you can cover the whole edge," wouldn't the knife position in the portion of my drawings that you quoted accomplish that?

Or would the knife position in one of the sequence of knife movements in the first part of my post with drawings be closer to what you're talking about?

Yes, you're position in the part I quoted will accomplish that... I'm just saying you don't specifically need to "find the center of the curve" and set the blade that way.

 

[jalapeno]

Thanks for clarifying.

How do you (or others) feel about the use of magnets to steady the knife on the table (especially for a knife you don't have to move to hit the full blade)?
I just don't see myself sharpening enough on these small knives where I'll develop the "muscle memory" to freehand hold them consistently.
I don't suppose it will actually magnetize a stainless steel blade, but I could be wrong (those magnetic kitchen knife holders would probably not sell if that were a problem).

How about, alternatively, double-stick tape?
I've use that a lot for woodworking jigs. Some double stick tape is as thin as scotch tape. The stuff I used is probably the thickness of 2-3 layers of painter's tape.

Another thing that just came to mind, again drawing on woodworking jigs, there are magnets with an on-off switch that are used on featherboards. I forget the name of them, but I wonder how that would work in this application. [edit: search for magswitch if you want more info on these]

 

[cbwx34]

How do you (or others) feel about the use of magnets to steady the knife on the table (especially for a knife you don't have to move to hit the full blade)?
I just don't see myself sharpening enough on these small knives where I'll develop the "muscle memory" to freehand hold them consistently.
I don't suppose it will actually magnetize a stainless steel blade, but I could be wrong (those magnetic kitchen knife holders would probably not sell if that were a problem).
...

If you do a search of the forum... I know there's several people here who have added magnets to the base to hold the knife.