Edge Pro Apex 4 Vs Ruixin

[Diemaker]

David, assume you are in line with the stone holder, directly perpendicular to the vertical rod. Are you saying that you can go out 45 degrees left or right from the center of the sharpening table and have no angle change? (Assuming a straight edge which lines up with the end of the table.)

Yes, as long as the stone holder remains perpendicular, at a right angle to, the vertical rod you can go 360 degrees. Think of a planar disk that sets on the vertical rod where the face of the stone intersects it.

Edit - I am wrong about this, it does not matter if the stone holder is perpendicular to the vertical rod or not, nor does it matter if it is perpendicular to the front of the table/knife edge. There is no angle change as the stone sweeps to the blade tip or heel. See post #75 for an explanation.

 

[Blues]

Gotcha, David. So I guess the solution is to sharpen every knife @ 21*...or...to keeping moving the section of blade edge being sharpened to the middle of the table...the way originally taught to use the system (especially with knives which extend beyond the edge of the table).

(Which would make the magnet, but not your slide guide, cumbersome, to my thinking.)

First world problems...though I take it you have a solution with your rig?

 

[Diemaker]

My current rig is an EP clone so it has the same issues. My preferred compromise is to clamp the knife in place with rubber and magnets located with the Slide Guide while sharpening. My angles so far are 15-21 degrees so the angle change at the ends of the blade are too small to worry about and more importantly the angle is very repeatable when I flip the blade, or the next time I sharpen it.

 

[maximus83]

P.S. Should I comment on why the sharpening angle changes over a straight line on my photos?

Yes would be helpful to have you expand a bit. But IMO, not on why the sharpening angle appears to change as you move along the blade--it's clear from your pics and comments what you were getting at there. It's the limitations of the measurement tool itself, you just need to have it completely perpendicular to the edge as the stone is, at any given point to get an accurate reading. So all good on that.

But it would be interesting to hear your thought on this related point that Diemaker made. That the sharpening angle changes as you move along the blade, any time the sharpening stone arm is NOT at a 90 degree angle to the vertical support. If this is true, then it's almost impossible to hold any kind of consistent angle unless you really go to an extreme with the technique mentioned in the Apex documentation, keep moving the knife a lot so that edge being sharpened is always in front of and perpendicular to the table. But if you do that, I'm still new to Apex sharpening, but it appears the resulting degree of movement as you're sharpening and lack of precision, means that repeatability between sharpenings kind of goes out the window. I'm using the slide guide and it helps somewhat with that, but I'm not sure I see a straightforward way to resolve this inherent limitation, if it's a real thing.

 

[fvdk]

This has all been talked about so many times before. With clamped systems, the angle does NOT change an the straight part of the knife, no matter how for you go from the pivot point. For a short answer read this post https://www.bladeforums.com/threads/angles-on-clamp-style-devices.1339022/page-2#post-15412040 but I would recommend reading the whole tread.

 

[Diemaker]

How the blade is held does not make any difference with how much angle change there is by sweeping the stone off-center of the sharpener when the stone rod is not perpendicular to the vertical rod. True that rotating clamps introduce other errors and inconsistencies to the angle that the blade is sharpened, both loading and when rotating while sharpening.

maximus83 - As long as you sharpened between 10 and 30 degrees the difference in angle change is minuscule, I don't think anyone here would ever notice this error. What error we many notice will come from other souces, and there are many. The biggest angle changes will be from the curved edge of pretty much all knives. Even though there is some inherent error in the current guided sharpeners they are still far more accurate than any other method of sharpening for us common folk.

 

[maximus83]

Even though there is some inherent error in the current guided sharpeners they are still far more accurate than any other method of sharpening for us common folk.

That makes sense to me--the idea that really given the inherent limitations of these systems you can't keep a perfectly precise angle throughout a blade--but in most common sharpening cases, the variation isn't enough to matter.

One area I admit I've struggled with at times in freehand sharpening, is on blades that have a huge, deep curved belly. I've been completely reprofiling this large cheap Schrade hunting knife, as a learning tool, it has a deep belly. The first night I just did a ton of heavy grinding, last evening I started to work the belly area more. I can definitely see that using the Apex sharpener I can hold a more consistent angle thru the belly and end up with a nicer looking, even bevel, compared to freehand. Even if the resulting angle is a few tenths of a degree 'off' from the straight edge angle.

 

[fvdk]

How the blade is held does not make any difference with how much angle change there is by sweeping the stone off-center of the sharpener when the stone rod is not perpendicular to the vertical rod. True that rotating clamps introduce other errors and inconsistencies to the angle that the blade is sharpened, both loading and when rotating while sharpening.

What matters is that the axis on which the pivot point is located, is perpendicular to the edge of the knife. As long as the pivot point is on that axis, the sharpening angle is constant, regardless the sweeping motion of the arm or where the pivot point is located on that axis. It makes no difference as you are still sharpening on the same plane.

If you did not get that from the tread I mentioned, than perhaps this video is will explain.

 

[maximus83]

^Yep floss illustration is very helpful visual for demonstrating angle doesn't change--as along as the edge is in a straight line. Curvy blades definitely change the equation though, I agree with that part.

 

[fvdk]

Curvy blades definitely change the equation though, I agree with that part.

Yes, that is indeed the case but you can minimize the angle change by carefully choosing where you place it in relation to the pivot point.
For example... if the distance between the edge of the knife (straight part) and the axis of the pivot point is 10cm than placing the curved part at a distance of 10 cm from the pivot point will keep the angle nearly constant throughout the curve. If however the knife steel is thicker at that point than the bevel will be wider even if the angle is the same. In such a case you will have to choose between keeping the angle the same but getting a wider bevel or keeping the bevel the same width but with a greater angle.

 

[Gritomatic]

With clamped systems, the angle does NOT change an the straight part of the knife, no matter how for you go from the pivot point.

F fvdk The law in your sentence is very important, but it's not 100% accurate. The angle does NOT change on the straight part of the knife, no matter how far you go from the immobile pivot point.
For a mobile pivot point, the angle can change the straight part. And this is what inventors of sharpeners with mobile pivot unit on the rail prefer to ignore.
The cause of the angle change on my photo is the same - the pivot point is mobile. In Edge Pro and Hapstone M/V series, the pivot unit is implemented in the same way - the pivot point orbiting the vertical rod. When you swing to the left, the pivot point goes away from you on Apex, towards you on Hapstone. When you swing to the right, the pivot unit goes in the opposite direction. When pivot point becomes closer, the angle increases.
1) I have created the conditions maximizing this effect. In real sharpening, it can be ignored. Diemaker is correct - when the guide rod is set horizontally, the effect is negated. I set a sharpening angle of 40 to have the guide rod far from horizontal causing 1.4 degrees delta. When you lower your angle to 30-35 degrees, the delta is less than the accuracy of digital angle gauges.
2) Angle change caused by Apex/Hapstone pivot unit is not important because it does not affect consistency because it will be always the same at any given point. It's similar to natural angle change caused by blade curvature, the aspect that can be fully ignored in sharpening.
3) Ben Dale has designed his sharpener with no intention to make long swipes. If Edge Pro is used in classic mode, a user should move a long blade to keep within the working table.

 

[fvdk]

When you swing to the left, the pivot point goes away from you on Apex, towards you on Hapstone. When you swing to the right, the pivot unit goes in the opposite direction. When pivot point becomes closer, the angle increases.

You are correct that the angle changes with a pivot point that rotates around the vertical axis as than the sharpening plane gets wider or smaller.
The angle does not change if pivot point only moves horizontally left or right on the pivot axis as with the design of the EZ-Sharp. The distance of the straight part of the knife edge is than kept constant to the axis of the pivot point.

 

[Gritomatic]

The angle does not change if pivot point only moves horizontally left or right on the pivot axis as with the design of the EZ-Sharp. The distance of the straight part of the knife edge is than kept constant to the axis of the pivot point.

I have explained in details, "I got bad news for EZESharp users" page 2, post 37
You need to perfectly align a straight part to the rail. Any misalignment causes the angle to change. And it works for one straight part. What for? The immobile pivot unit gives all straight parts the constant angle.

 

[fvdk]

The rail on which the pivot point moves from left to right is perpendicular to the edge of the knife.
You do not seem to understand that the distance of the pivot to the edge of the knife does not change and because of that, the angle also does not change.
If you use the Edge Pro like it is intended, moving the knife so you are sharpening the part that is on the table, than the angle does not change.
There is no difference in moving the blade from left to right with a fixed pivot point or keeping the knife in place while moving the pivot point from left to right.

 

[Diemaker]

When thinking about this I think of replacing the stone and holder with a plate of glass, ie a plane. Now envision how that plane and the knife edge lines up. Attaching lines from the pivot to the blade in the video is interesting but he needed to put the lines at opposite ends of the blade and then the center. When I have time I want to explore this some more by setting it up on a machine table to get it all dialed in. Something with a dead level surface where I can put an indicator in the spindle and make sure the straight edge is level and parallel with the sharpener.

 

[Blues]

When thinking about this I think of replacing the stone and holder with a plate of glass, ie a plane. Now envision how that plane and the knife edge lines up. Attaching lines from the pivot to the blade in the video is interesting but he needed to put the lines at opposite ends of the blade and then the center. When I have time I want to explore this some more by setting it up on a machine table to get it all dialed in. Something with a dead level surface where I can put an indicator in the spindle and make sure the straight edge is level and parallel with the sharpener.

Yeah...something you can do with all that spare time of yours.

 

[Diemaker]

Better yet I think I just had a good idea! How about think of this question by replacing the stone arm with a plate of glass on the sharpener that freely pivoted at the same spot. Now lay that plate of glass on the knife like your going to sharpen it. How well does it contact? I think pretty good, and no angle change as you move away from the center since it is a flat plate of glass that pivots freely in the middle. This is an interesting question since the whole point of a guided sharpener is accuracy and consistency.

Now back to my website.

 

[bucketstove]

Better yet I think I just had a good idea! How about think of this question by replacing the stone arm with a plate of glass on the sharpener that freely pivoted at the same spot. Now lay that plate of glass on the knife like your going to sharpen it. How well does it contact? I think pretty good, and no angle change as you move away from the center since it is a flat plate of glass that pivots freely in the middle. This is an interesting question since the whole point of a guided sharpener is accuracy and consistency.

Now back to my website.

Hello
Ozale0abvbY Wicked Edge Angle Study - Snecx Tan

 

[fvdk]

Now lay that plate of glass on the knife like your going to sharpen it. How well does it contact? I think pretty good, and no angle change as you move away from the center since it is a flat plate of glass that pivots freely in the middle.

Correct. A lot of people see it one dimensional but the horizontal axis of the pivot and the edge of the knife are not a single line but one plane of the triangle and as long as pivot axis and the edge of the knife are perpendicular, everything in the plane is the same angle.

 

[scottc3]

Thank you for links fvdk, I downloaded Lagrangian's study and I am building understanding of the practical limitations of the various guided sharpeners now, but... It took reading this thread at least 3 times and digging thru the others. I was thinking it was time to call an old friend who designs buildings, explain my grappling for understanding, and ask for math sentences and pictures of the 3 planar (and apparently) conic conditions against straight and curved edges, but Lagrangian's study is a detailed help. I noted that EdgePal inventor David articulated precisely what several here are saying, begin by approximating zero degrees as device level, a line going thru 90 and 180. And keep that level at systems interface to edge. With EdgePro, practice staying around 21 degrees to perpendicular for minimal angle variation.
Bucketstove. gotta ask cause I'm always asking why, and ~24 is seriously different then ~34/6. Your post is new so my brain is trying understand why delta between pivot and edge angle. Part of me suspects the angle cube's gyroscope is not fully implemented (hows that for stubborn minded- gish).
Is it possible to just tell us what happens when holding angle cube like it was a pin-wheel pinned to stone, in cubes center, so cube stays in vertical orientation, freely rotating left of right movement and visa-versa, the stones plane? Or use an iPhone and angle finder app to eliminate the possibility (I know the iPhone hardware is fully implemented, though app maker's software hooks may be off... that's another story, but do not know the angle cube)?
relative to sharpening really long edges-
My personal sword sharpening solution was buying Ron's KME Axe sharpener. The sword in question is wide enough spine to edge that it will work. And the Axe sharpener's stone holder does not rise high enough to be an angle problem practically speaking. I'm also re-purposing it for kitchen knives longer then 10 inches or so, by fabricating a simple knife holder. But you can bet after reading these threads, I'll be 1, keeping the Gritomatic stone holder perpendicular to slide, which should be good nuff. And 2, mocking up using my bench vise before fabricating knife holder. In hindsight Ron's original solution was for broadheads, never longer then traditional pocket knives, but his new broadhead sharpening solution can be used with any stone! Yes, ya gotta check it out if your driving them thru game big enough to hurt you if their just wounded. Safety first.