WTF is wrong with my EdgePro Apex?

Noctis3880

Noctis3880

Joined
Jul 22, 2009
Messages
11,409
Honestly, I can't get my head around what the hell is wrong with this thing.

I haven't been using it too much, probably not enough to merit flattening the stones, especially the fine grit ones. But only today, after doing some light "testing" using the 600 grit stone to remove my sharpie marks on my factory edge Kershaw Shallot did it finally dawn upon me that something is seriously messed up with it.

To sum it up, the angle when grinding one side will drastically change when grinding the other side of a knife. The angle difference seems to be about 6 degrees or more(which becomes painfully obvious when you grind down the knife enough to raise a burr). I KNOW it's not how I hold the knife with each hand, because I rest it on a stable flat surface on the knife with considerable pressure. I KNOW it's not because the stones aren't flat, because there's no chance in holy hell that I wore down the 600+ grit stones enough to make it uneven.

My only theory so far is that one of the plastic legs is shorter than the other, or the joints don't rotate all the way, which makes the table crooked. Though it doesn't seem obvious enough to stand out to the naked eye, and I'm not sure how to go about checking it.
 
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I was having the same problem with mine, the front of the knife would be perfect and the back would be a HUGE bevel, it has to do with pressure, and the way the knife sits on the platform.

But since you already mentioned that IDK. Every now and then I'll put a bigger bevel than I would want to with the Edge Pro, especially with knives that are very thick.

I would like someone who has got that down to a perfection with the thick Busses to show me how they do it, I only use it to do folders really, and small fixed blades, which I do a pretty good job with, just those large, thick knives, I cant get it down to a science.
 
The blade profile on your Kershaw knife is uneven, so the angle on one side would be more acute than the other side.

Also, check the spine on your blade to see if it is even.
 
I'm not too sure what the "spine check" is, and I find that I can't rely on tests where you have to judge by eye, because I constantly second guess my own judgements. I need something absolute, almost scientific, but I don't want to shell out $50-$100 just for a sure answer.

However, I do have some evidence that might confirm uneven angles. When I strop my knife(on diamond spray loaded leather, which doesn't seem abrasive on any level at 200,000 mesh, making me doubt if the diamond is actually real), I notice that the left side of the blade(blade pointing away from me) appears to have a higher angle than the right side, which is consistent with the results I have using the edge pro. When holding the knife in my right hand and using the left hand to hold the arm, I'm sharpening the left side of the knife, and the marker removed is away from the edge, suggesting that the angle is set too low.

However, I'm still not 100% certain of it, and even if I am, I don't know exactly how to fix it. Although I have a theory on how to go about it, even if I don't like it. I plan to lower the grinding angle so that both sides need to be ground down before the sharpening reaches the tip. When it does, I sharpen the "shorter" side until both sides appear to have the same "thickness" or length of metal at that angle. Personally, I'm not all that eager to remove so much metal, especially considering I'll need to use a diamond stone to do it on S110V.
 
Most likely the blade profile on one side is thicker than the other, so it'd need a higher bevel for the same angle.
 
I've noticed similar things. I don't think it is the fault of the EdgePro. Rather errors in the original factory blade grind! What I finally concluded is that the kinfe's reference planes on each side (the planes you rest on the blade table) are sometimes not symetrical. I would put a perfect 30 degree inclusive bevel on a blade and then try and touch it up on a SharpMaker set to the same angle. One side of the bevel might match ok but the other wouldn't even register! Very aggravating! See the SharpMaker is used by keeping the blade axis vertical while the EdgePro is referenced to planes on either side of the blade axis and these planes are not necessarily symetrical (the angle between the blade axis and the reference plain is not the same on each side.)

A similar gripe is when the factory edge is not centered in the thickness of the blade. The bevels may look "even" inspite of this, but only because the factory bevel angles are dramatically different from one side to the other. If you try and put the same bevel angle on each side you end up with a bevel on one side that is twice as wide as the other. Again, very aggravating!
 
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You have two grinds on most knives. The primary grind makes up the full or a portion of the width of the blade. The edge grind is the second. Some have a secondary bevel behind the apex or edge which would be a third and still others have separate grinds for a tanto tip or some other such things but whatever the case may be for how many grinds the one we are interested in is the primary grind on both sides of your blade.

One side is probably taken down more than the other which means even though you have the sharpener set at the same setting it makes for a different width to the bevel on each side. If you notice on some knives there can be a different width to the tip, the middle, the back or a combo mixing and matching all three on just one side. Its all about how evenly the primary grind may or may not be as to how your bevel comes out.

Lets look at it from the stand point of two different blades.

Take the Buck Strider 881 as an example. This model has a very thick stock blade of 4.5 mm thickness. The primary grind and bevel are both thick and obtuse for strength so an 18 degree bevel is going to look very wide on that blade. Take your thin paring knife from the kitchen and sharpen that at the exact same bevel angle on your sharpener and you will note that the bevel is thin. You cannot tell the angle from how wide or how thin the bevel looks. Its why we need sharpy markers and a bit of patience to determine where it is on your sharpener.

Anyway, there is nothing wrong with the sharpener.

By the way, I would think being that this is a forum viewed by many that it would be a good idea go back and edit out the "F" words in your posts. Vulgarity on these public forums is something I don't like seeing here personally. If it was the Wine and Cheese forum or the Pirates Cove hey have at it. I mean we all do it there and cut loose but this is not the place for it since some younger folks and parents may not like it much.

STR
 
I also had the same problem when I first used my DMT aligner. Roger and STR hit it on the head, I find that almost all knives have different grind angles some more obvious than others. It can be a PITA sometimes because you want your bevels to be even but it just not gonna happen unless you make two different angles on your blade.
 
It is rare to find factory knives with even grinds. After years of putting on very thin angles it becomes pretty obvious if the grinds are uneven since the bevel become very wide on factory thick edges. Like the others said I would blame the factory blade grind more than Edge Pro. The Edge Pro does have a bit of a learning curve and I prefer freehanding over trying to find just the right spot for the knife on the blade table. I just don't see how that system could be off by 6 degrees, though I definately have seen factory grinds that far off.

Mike
 
Yes, but would the best way to fix it be to grind both sides at the same angle, then grind down the "short" side until both sides appear to be the same length?

Also, I seem to have a tendency to "miss" the part of the blade closest to the handle when grinding, so that part tends to have a higher angle than the rest of the blade. Do I simply make a straight grind on that area without moving the stone over the rest of the blade in order to fix that? Because when I tried that on my Endura, the blade had an almost "flat" appearance on that one small spot, like somebody crushed my blade with several tons of pressure.

The edge on my Shallot actually looks pretty nice as it is, so I wanted to avoid an excessive change in the edge angle, or too much grinding. Perhaps very slow grinding and light pressure on an extra fine diamond stone will be enough?

I've also been trying to remove the fine "grind lines" from the factory edge by stropping the edge on diamond crystal loaded leather(200,000 mesh), but the work has been slow if it went anywhere at all(considering I only paid $11 a bottle, I'm a bit suspicious on whether or not it's actually diamond at all). Stropping on a recurve seems ridiculous since I only use a loose strip of leather resting on a flat surface(I don't bond it to anything). I was thinking of spraying some of that diamond polish on a Scotch-Brite sponge pad and simply strop it on that so that it can follow the curves better.

In any case, I want to avoid causing unnecessary damage on my Shallot unless I'm certain I can do it right.
 
This happens to me all the time when the edge isn't centered. It's especially obvious with the Busse "asymetrical" grind. I just don't let it bother me anymore. If you are using the EP correctly, the primary angle will be the same on both sides no matter how wide the grinds are.
 
I've seen two common problems when using the Edge Pro:

1. Edges that aren't centered. Sure, you could make it perfect with the Edge Pro, but you'd have to remove more steel.

2. On most knives I've sharpened with the Edge Pro, the edge bevel gets larger, sometimes a lot larger, as you near the tip. Strangly, I've seen exceptions to this in cheaper knives (Byrds and a Becker BK-11).

Some people get the Edge Pro with the expectation of visual perfection. I've grown to appreaciate it as a good way to thin an edge at a consistent angle and to then put a good polish on that edge.
 
The grind lines on the edge are probably 120 or 200 grit from the factory. using 200,000 mesh diamond spray to strop the grind lines away is an exercise in futility. Start with 400 grit wet/dry automotive sandpaper and work up.
 
KeithAM said:
On most knives I've sharpened with the Edge Pro, the edge bevel gets larger, sometimes a lot larger, as you near the tip. Strangly, I've seen exceptions to this in cheaper knives (Byrds and a Becker BK-11).
Click to expand...

The EP maintains a constant angle, so obviously you have to account for any increase in the radius the stone is traveling on.
 
KeithAM said:
Thanks for stating the obvious! :thumbup:
Click to expand...

Your post made it sound like that was a mystery variable. Sorry if I read it wrong.

You've got a piece of metal and a piece of stone coming together at an angle. If you want a uniform secondary bevel, you have to maintain the angle of attack.

The stone's angle stays uniform until you change it. You control the radius. The primary grind angle is built into the blade.

Das what it is.
 
Roger999 said:
Most likely the blade profile on one side is thicker than the other, so it'd need a higher bevel for the same angle.
Click to expand...

That's it. We call it asymmetric bevels. If you don't like it you can simply grind more on the side with the short bevel. If you want to make that correction just grind three times longer on the short side. After severl sharpenings things should even up.
 
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