Okay, here's kind of a weird question regarding angles and guided sharpeners.

[KennyB]

So a while back I posted about the way I was using to measure the angle for my sharpening. I would take a pair of calipers, and measure the distance from the spine of the knife to the sharpening stone, then measure the width of the blade and use a little trigonometry to find the arcsine of the angle this created. To make things simple and not get into a big math discussion, I'll just write the formula in practical terms...

Angle = asin(d/w)

Where 'd' is the distance from spine to hone, and 'w' is the width of the blade. This gives you the angle that you're holding the blade in relation to the stone.

Okay, nice and simple right? Well then someone comes along and tells me that unless I have a zero ground knife, that because of the primary grind angle the edge angle I'm going to wind up with will not actually be the same as the angle between the blade and the hone. But I figured since you know, people generally just hold the knife blade at what they think is 20 or 25 degrees and some even put angle guides on the stone to measure it in the same way, that I'm fine...

Well here's my question: Don't systems like the Lansky and the Wicked Edge also go by the angle of the sharpening medium in relation to the blade? So if the way I detailed to measure it didn't actually give me the edge angle, then aren't these systems subject to the same thing? So if a person sets their Wicked Edge or Lansky to 30 degrees inclusive, aren't they actually going to get an edge that's a few degrees more acute or obtuse than they think?

 

[BluntCut MetalWorks]

If distance 'd' starts from hone to apex-to-spine line end point, then the triangle is exact regardless of blade & edge geometry. When an edge/apex is off-center (e.g. chisel/single-bevel extreme case), obviously any type of sharpeners need to take this into account and adjust angle per side.

Kenny - your way of calc is correct & flexible. For me - calc the bevel angle, I can use a fine ruler(too lazy for caliper) to get 'L' bevel face length, 'W' blade thickness at bevel shoulder, plugs these values into http://ostermiller.org/calc/triangle.html

 

[sintro]

Yes, the angle varies on thickness of knife, and how far out the top of the clamp it is.

 

[KennyB]

If distance 'd' starts from hone to apex-to-spine line end point, then the triangle is exact regardless of blade & edge geometry. When an edge/apex is off-center (e.g. chisel/single-bevel extreme case), obviously any type of sharpeners need to take this into account and adjust angle per side.

Kenny - your way of calc is correct & flexible. For me - calc the bevel angle, I can use a fine ruler(too lazy for caliper) to get 'L' bevel face length, 'W' blade thickness at bevel shoulder, plugs these values into http://ostermiller.org/calc/triangle.html

Yeah I've been using the way you listed a while now after being told the original way I was doing it wasn't given me the exact angles. I thought I had confirmed this once by measuring the angle the way I do it, and then measuring the way you do it and seeing a 1-2 degree difference, but this might have just been accounted for by the difficulty of taking precise measurements with calipers at the cutting edge--it can be hard to get the points of the calipers right on the bevel's shoulder.

Interesting that you use a scale. I can't imagine how one could get the "W" figure for thickness with a scale. Any way you could take pictures because I'd be kind of interested in that--I'm always dinging the edge up with the calipers and having to sharpen again after checking my angle. Which is fine during the grinding process, but gets annoying if all I'm wanting to do is check an angle on an already-sharp knife.

 

[sticktodrum]

To avoid the degree markings on my Edge Pro, I use an angle measure. Most of my blades have a flat, unground area, and I take that as the 0. It sits flush on the table (or within a clamp for another system) and then measure the angle where the stone touches the edge to be sharpened. For blades without a flat area, I zero the gauge at the pivot on the handle, and it works out similarly.

 

[BluntCut MetalWorks]

I score clay/wax/gum/balsa to bevel shoulder depth, use my usb microscope calibration ruler to measure the width. I do cross-check this with the caliper to make sure I am not too far off and adjust some if need to. yeah, I hate to nick the edge with the caliper too.

 

[duro]

I must be lazy. I Just set the wicked edge, and roll with it. I bought an angle cube, but don't use it. I guess my sharp knives could get sharper?

 

[OHALLUM]

You guys are getting way over my old hard head. Interesting reading and theories, behind all your methods. My question is does it really make a big end result difference if the resulting sharpening job is 1 or 2 degrees off the target? Does it really effect the ability of the knife to do it's intended job of cutting something? Does close really only matter with horseshoes and hand grenades? Just some thoughts for me to ponder. (thick skull, over used grey matter) I know, too many questions for one posting!

Blessings,

Omar

 

[KennyB]

You guys are getting way over my old hard head. Interesting reading and theories, behind all your methods. My question is does it really make a big end result difference if the resulting sharpening job is 1 or 2 degrees off the target? Does it really effect the ability of the knife to do it's intended job of cutting something? Does close really only matter with horseshoes and hand grenades? Just some thoughts for me to ponder. (thick skull, over used grey matter) I know, too many questions for one posting!

Blessings,

Omar

I don't think that 1 or 2 degrees matters performance wise, but it's more about being able to properly communicate user experiences for me. If I was going to tell someone a specific knife or steel worked well for a particular task at a specific angle, then I want a way to ensure that the angle I'm reporting is correct, and visa versa. I don't think it's really a tremendously big deal, but when you have the tools to be able to measure the angle precisely it's just nice knowing exactly what you've got.

In all honesty, I think if two people had a knife "about 30 degrees inclusive) and one was really 29 inclusive and the other really 33 inclusive, then there probably wouldn't be too much of a difference there. However, imagine if two people had a knife at 35 degrees inclusive and the other at 25 degrees inclusive, and they both thought they were working with a 30 degrees inclusive edge. Well, when the guy with the more acute edge says, "Mine cuts this like crazy," the guy with the 35 degree edge might be saying, "I really didn't notice a performance increase"; and on the other hand, the guy with a 25 degree edge might say, "It just doesn't stay sharp long enough," where the one with the 35 degree edge wouldn't have the same experience. When you so often hear people professing that 30 degrees is significantly better than 40 degrees, you don't want to have that big of a discrepancy as that between 25 and 35.

Really it doesn't matter since most of these things will be perceived differently just be merit of the way people cut, materials, differences in levels of sharpness, refinement, etc. But like I said it's just nice to know that you're on the same page with someone. It's kind of like before they came out with a standard for the inch... One person's "inch" was shorter or longer than the next one. I just like to know how to properly measure my knives so that my "30 degrees" is the same as everyone else's.

 

[OHALLUM]

I totally agree with all you said. My remarks, questions, were more tongue in cheek than deluding all the discussions. I have sharpened some knives to a "mirror" finish, and have not used the knives since, but only use them for "show and tell". They would in the real world I would use them for not cut any better or worse than the knives I normally sharpen for EDC and use. I enjoy sharpening my knives more than using them, and if I could afford a system to accurately bevel to a + or - 1* bevel, I would have one. If for no other reason than "bragging rights". That is where I am coming from, and in no way would I find fault with anyone's attempt at perfection. That is after all what we all are striving for in our own limited (whether financially or in ability) way. Good discussion.

Blessings,

Omar

 

[Swoop03]

My question is why do you need to have your edge precise down to the minutes and seconds of a degree?
Yinz all talk about having precise angels, but truely they're not unless you calculate everything, then you have to account into flex of the rods on the sharpening system or flex in the blade. There are so many things that could come into play, if your stones are worn out and slightly shallower or concaved in the center that will throw it of a little bit. What if the blade isn't perfectly straight or bent or warped in the slightest. All of these things will add up and you could be a degree or two or more off what you calculated and what your angle cube or what have you says.

Its all too much for an anal machinist like me. To many variables, if I ever got one of those high end systems I'd be hell bent on making everything so perfect I'd grind my blades to nothing before I'm happy lol. I just stick to hand sharpening and if it looks even I'm happy and satisfied because I did it with my own hands

 

[Chris "Anagarika"]

Kenny,

I do agree in the quest to perfection, and accuracy of comparing notes. However, since I always free hand, and rebevel each knife by 'feel', I have to side by swoop03

So my blades are between 25-35 depends on my feel

 

[Nosmo]

My question is why do you need to have your edge precise down to the minutes and seconds of a degree?
Yinz all talk about having precise angels, but truely they're not unless you calculate everything, then you have to account into flex of the rods on the sharpening system or flex in the blade. There are so many things that could come into play, if your stones are worn out and slightly shallower or concaved in the center that will throw it of a little bit. What if the blade isn't perfectly straight or bent or warped in the slightest. All of these things will add up and you could be a degree or two or more off what you calculated and what your angle cube or what have you says.

Its all too much for an anal machinist like me. To many variables, if I ever got one of those high end systems I'd be hell bent on making everything so perfect I'd grind my blades to nothing before I'm happy lol. I just stick to hand sharpening and if it looks even I'm happy and satisfied because I did it with my own hands

The reason I strive for the maximum precision in angles and quality of workmanship in a guided system is all about re sharpening a blade.
If you can 'duplicate' the exact settings you used originally, re sharpening ( matching the bevels exactly ) is super fast, with the absolute minimum of metal removal. This to me is one of the main benefits of either the EP or WE systems.

 

[Swoop03]

The reason I strive for the maximum precision in angles and quality of workmanship in a guided system is all about re sharpening a blade.
If you can 'duplicate' the exact settings you used originally, re sharpening ( matching the bevels exactly ) is super fast, with the absolute minimum of metal removal. This to me is one of the main benefits of either the EP or WE systems.

That does make sense, to match the edge already on there that you or the factory put on it. I'm not to worried about wearing any of my knives out though. It'll take a long long time wear one out. I do have a lansky and the only thing I use it for is thinning out an edge or fixing a screwed up factory edge on a cheaper blade. It's easier quicker and makes a more consistant edge than my hands. Past that though I hand sharpen. The only thing I like about those systems is the ease of getting a mirror edge it seems. It takes quite the steady hand to do that free hand. I've tried mirror polishing by hand. I don't have fine enough stones so when I go to a strop I spend a large amount of time stropping only to have a shiny edge with tacky scratches in it.