Edge pro angle measurement

R

RipD

Joined
Dec 10, 2014
Messages
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Is there a standard reference most people use for setting Edge Pro angles? I've watched a ton of videos and read a lot of instructions. Most of them seem to be wrong.

The bevel of a blade edge is relative to the center of the blade, not relative to one side of it. On the EP if you measure the table angle you're measuring where one side of the blade is. If you measure the stone resting on the table you assume your blade is at the table edge. This never happens - there's always some overhang.

For a thin blade with very little overhang this is probably negligible. But it's still wrong in terms of how the angle should be measured.

I view my blade as a wedge and measure my angle relative to the center of blade. This takes an extra couple of minutes and may be more work than most people want to do. Is there an easier process I'm missing?
 
I had an Angle-cube and sold it. It was seldom used, and I saw no reason to get that precise.
Am I correct when I assume that you are splitting an angle into several parts with your references
to blade "center" versus blade "edge?"
I will generally re-profile my blades to be either approximately 17 deg per side,
or 20 deg per side... Seventeen for knives doing double-duty in the kitchen, and
twenty degrees per side for my "heavy-duty" fixed blades.
20 deg per side is also what Spyderco uses for their Military model, for instance, and this makes for easy
resharpening for those folks who use the SharpMaker.
 
Yes, splitting in half. For a thick blade the difference is a couple of degrees or more. I get that if you're approximating it doesn't really matter provided that it's consistent on both sides.

I'm asking about how to get to a specific angle. It seems that many people trying to how to do this are getting it wrong. Or I'm misunderstanding something.
 
Easiest way is to use an angle cube on the knife blade zeroed out on the Apex table, then divide in 2. Something I keep in mind but don't bother with on my knives.
 
Diemaker said:
Easiest way is to use an angle cube on the knife blade zeroed out on the Apex table, then divide in 2. Something I keep in mind but don't bother with on my knives.
Click to expand...
Got it. Zero on the table, then get the angle of the blade and divide by 2. That works.

cbwx34 said:
Have you watched the EP video on how to do it?
Click to expand...
I have watched the video. I don't see how this can possibly be correct. It discounts the blade thickness. For a thin knife it's probably close enough. For a thicker knife it can't be. I can can draw some pictures and post them if you want me to explain why this is.
 
It's all relative.
And if you don't have a relative that can show you this let me say this about that :

All kidding aside (mostly) you can see I take the angles of my woodworking edge tools seriously because in some cases a couple of degrees can make the difference between a dinged up edge and a nice clean cut that lasts a relatively long time. (there's that word again).
And it is very easy with the Varitas jig and combined with the fact that these blades are single bevel to get a high degree of accuracy and more importantly CONSISTENCY in the edge formation. Now the wood doesn't know a degree from a sausage but as long as I find an edge geometry that works and am able to duplicate it over and over and over until the project is completed then that is all the wood requires.

That said when it comes to a pocket knife, well one of my pocket knives anyway, I chuck a stone into the Edge Pro, lower the guide for the rod way down, ink the edge of the knife, set the edge on the table and take a pass with the stone. Judge where the stone is hitting on the sharpening bevel and adjust the stone until I am on the apex. Flip the blade and try that side in the same way. If it is one of my knives I have sharpened / reprofiled then I am good to go and just duplicate what ever freakin' angle is there because I know it works.

If the edge is a factory edge I think back to how the knife performed FOR WHAT I CUT WITH IT and if it was less than stellar I adjust the stone angle to improve the performance and reprofile the edge. I do the same with the woodworking blades but since the Varitas jig allows me a scale to fool with I write the angle on the blade.

If the knife or the woodworking edge doesn't perform as i need it to then I make another change accordingly.

With the knives I don't give a flip what the degree number is just that the knife is working well for me . . . when it comes to knives it usually is the lowest freaking angle I can put on it so often I just keep cuttin' 'er back until I get edge dings or I can't stand all the ecstasy of how great a low sharpening angle is working for me (see my posts about my "Little Monster").

Short answer : If you want the true numbers for the edge that works for you (once you have found it by trial and error) do some math dude. Trig and some addition and some traction should take care of it. Don't forget to check that your work surface is level or put the dif into the equation. Assuming you are using an angle cube. I don't own one but I have other bubble protractors etc that I would drag out if I cared.

Murry says it all here in this vid :
(basically it is how the edge performs not the angles from a book) . . . thinness behind the edge is almost more important than the final edge angle when it comes to a knife. Grind the crap out of that sucker or use Japanese knives. :thumbsup:
Varitas Finish Plane blades lined up for inspection.jpg
IMG_0203.JPG
 
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Wow... ok. So you're the third person to tell me that angles don't really matter for pocket knives. I get it and I understand. Thanks for telling me that. I'm asking specifically about getting a specific angle on an EP and suggesting that explanations I'm seeing, even from the EP inventor, are wrong. I leave most of my knives at the factory bevel unless it's really not working for me. That's a different discussion.

Short answer : If you want the true numbers for the edge that works for you (once you have found it by trial and error) do some math dude. Trig and some addition and some traction should take care of it. Don't for get to check that your work surface is level or put that in the equation. Assuming you are using an angle cube. I don't own one but I have other bubble protractors etc that I would drag out if I cared.
Click to expand...
I am doing the math. That's how I know (or strongly suspect) that most of the explanations I'm seeing are wrong. Or I'm misunderstanding something. (FYI, not using any trig functions. I can get there with all right angles so Pythagoras is helping just fine. And I only need geometry to check that my thinking is correct. I can get to the blade angle just using an angle measuring tool and addition/subtraction.)

This question seems to have irritated some people. Certainly not intended. I get that many of you don't measure angles on your EP, and I'm not saying that you should be doing this. I have a need to set specific angles. Just wondering if there's a better/easier way to do it. Was actually looking forward to a discussion and an exchange of ideas.
 
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I place a blade on a flat surface and put an angle cube (zeroed on flat) on the blade to measure the total angle of the primary grind (A).
Then put the blade on the Edge Pro stage and measure the angle of the stone (B).
The edge angle should be 29.5-B-A/2, where 29.5 is the angle of the stage from the flat surface.
 
RipD said:
...
I have watched the video. I don't see how this can possibly be correct. It discounts the blade thickness. For a thin knife it's probably close enough. For a thicker knife it can't be. I can can draw some pictures and post them if you want me to explain why this is.
Click to expand...

No need... I thought about it, and you're right, if you use the degree markings on the EP and followed the video example, there would be a bit of an error. I think if you used an angle cube for step one, you would eliminate the error. But, it might be just as easy or easier to use the idea Diemaker or miso2 suggested.

Good catch! Any idea how big the error is... maybe using the dimensions of a knife you're currently working with?
 
miso2 said:
I place a blade on a flat surface and put an angle cube (zeroed on flat) on the blade to measure the total angle of the primary grind (A).
Then put the blade on the Edge Pro stage and measure the angle of the stone (B).
The edge angle should be 29.5-B-A/2, where 29.5 is the angle of the stage from the flat surface.
Click to expand...
Excellent! Now that you wrote it down it's obvious! Thanks much. That's a nice, concise formula. I'm doing the same thing but was taking the long way. I don't trust the table to always be at the same angle due to the suction cups so I measure it or us it as the zero angle.

No need... I thought about it, and you're right, if you use the degree markings on the EP and followed the video example, there would be a bit of an error. I think if you used an angle cube for step one, you would eliminate the error. But, it might be just as easy or easier to use the idea Diemaker or miso2 suggested.

Good catch! Any idea how big the error is... maybe using the dimensions of a knife you're currently working with?
Click to expand...
It will depend on blade thickness and distance of the edge overhangs the table. For a thick blade it could be a couple of degrees or more. For a very thin blade it's negligible.
 
RipD said:
This question seems to have irritated people.
Click to expand...
Nah . . . most every thing irritates me in one way or another.
That and I have a sense of humor that pleases me and irritates others.

One thing to keep in mind with the "A/2" is that many blades are not symmetrically ground. Some times the flat of the blade stock is on the table and the main grind is then up off the surface.
If the edge is not centered on the spine (knife is ground off center) then got to take it from there. Does that make sense. I'm not sure it makes sense to me. I just know that some grinds are off center in relation to the spine and pivot axis.

As you probably know factory sharpening bevels are notoriously asymmetrical. A sharpening jig brings that into sharp relief big time and part of the reason I cuss the whole time I am putting my first edge on a factory knife *%*@^$**(%*$^&(*!!!!
 
wow,

All good. Completely agree on the symmetry issue. That's why I starting with "assume a full flat grind" which I also assume is symmetrical. And agree that some factory edges are not great. Just did a Kershaw that was ~18 degrees on one side and may ~21 on the other. Crazy. If the blade itself isn't symmetrical I'd probably just take the knife to a stone. Seems like too much hassle for the EP.

btw, gotta love Murray Carter. I have one of his kitchen knives and have chatted with him (friend of a friend).
 
Visual.

Edge_angle.jpg


The stage angle may vary depending on the device.
I constantly get 29.5° on my apparatus.

This method only works well for flat ground blades.
May work fine for hollow, but not for convex.

As pointed out above, if the primary grinds are uneven, you will get uneven edge bevels.
 
Here is something else that came to mind. I don't have one. It might be useless for a knife blade because the slots are kind of wide but see what you think. It can be had from sharpening tool vendors and woodworking tool vendors.
6253000.jpg
 
I have one of those I've used for ax edges, WB, but I never tried it on a knife due to the width of the slots.
 
Great visual, miso2!! While you were doing that, I was not spending time with my kids and did this to try and explain why the table edge doesn't work to set the angle. Likely full of typos and could use another explanation page or two. Let me know if this doesn't work and I'll try again. Making sense to me and making sense are two different things.

The only time I tried one of those angle things I had the same problem - my blades were generally too thin. That would help see what angle a knife has. It won't help you set an EP angle that's different from what a knife has. (Hope that makes sense.)
 
I think it makes sense.

I measure the angle of the stone, when it is set on the blade but not on the table edge.
So, it doesn't matter how much the edge sticks out from the table edge.

Edge_angle2.jpg


I found most knives have 5 - 7 degree primary grind.
So you subtract 3 degree off and can get an approx. edge angle.
 
Here's a video by the TheApostleP that helped me a lot. I que'd it to the part about figuring the angles but the whole series is helpful. begins @5:24
 
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