Knowing the edge angle, is it beneficial?

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2BSharpAgain

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Feb 28, 2019
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NewBe here. I have been following this forum for a while and thought y'all could help me with a question. I am wide open to your comments and opinions.

I have been sharpening for fun and money for 50+ years and consider myself a good functional sharpener. I have a reasonable working understanding of the edge angle and the trade off between sharpness and life, and the other variables that affect overall performance. I can't determine the type of metal the knife is made from, other than carbon steel vs stainless steel, and it usually does not matter when I am sharpening. The owner just wants the knife sharpened.

I have always had a problem determining either the existing or newly sharpened edge angle. Hand me a knife, ask me the edge angle, and all I can do is make an educated guess. Can I be within +- 5%?, only with luck. To help me, I purchased the CATRA Laser Knife Edge Protractor, $300+, and now I can actually see the measurement of the edge angle. I believe it helps me sharpen better and to provide consistent results.

My question is:
Does, or would, being able to accurately read the edge angle, improve your ability to sharpen?
 
It would not help my ability to sharpen, right now as I free hand sharpen. If I had a sharpening system that mechanically held a preset angle, it would reduce the amount of material removed if I would maintain the same angle.

I don’t think it’s worth that $300 for that product, that you are advertising?!?!?!
 
You can approximate the edge angle easily using a few different methods. One is to lay the blade flat on a hard, flat surface and slowly raise the spine until you see the edge just contact the stone. Another is to take piece of hard flat material softer than the blade and do this same thing, only (using very light pressure) keep lifting the spine until your edge just barely bites. You can also use a digital protractor rule to take a direct measurement with reasonable accuracy.

More and more accurate information can assist your learning process. The question mostly comes down to value and cost-effectiveness for that learning process. I don't think you really need a $300 CATRA laser goniometer. But if you have the cash and the investment doesn't phase you, it sure won't hurt. Just be aware that they can have a hard time registering properly on convex edges compared to physical ones.
 
I'm really not particularly interested in knowing the angles or degrees in and of themselves, unless I was using a jig to specifically reprofile or to maintain the same bevel from one side of the blade to the other.

I really only care how the knife performs for the intended task.
 
Blues said:
I'm really not particularly interested in knowing the angles or degrees in and of themselves, unless I was using a jig to specifically reprofile or to maintain the same bevel from one side of the blade to the other.

I really only care how the knife performs for the intended task.
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Ah, but the angles impact that drastically, and knowing the angle range in which you, for instance, start experiencing instability in the edge, or what ballpark to shoot for to optimize the performance of the tool for its intended context...that's useful. You don't need ultra precision or anything, but having a reasonable approximation of the values is good. A lot of people who are experienced sharpeners will simply internalize muscle memory based on experience, but then that makes communicating what they're doing to others nearly impossible without visual aids. :)
 
Well, of course the angles impact the result...but when I lay my blade on the hone I have a pretty good idea of whether I'm over / under, say, twenty degrees or so, just from experience with lots of custom and production knives. I really don't care about the number per se.

If a good, clean thin edge is superior for the task, so be it. If something more robust suffices, well, there it is.

I've never measured an angle, though I have employed them as supplied on Sharpmaker, Edge Pro, and clamping systems like one finds with GATCO, Lansky, DMT et al. So I guess I have an idea of whether a bevel is more or less acute / obtuse than the common settings found on those devices.

Freehand, experience seems to be the best teacher. (Though I've been known to be delinquent when I should have been in class.) On a system, however, there'd be no good reason not to use the settings, imho.

Anyway, we don't disagree. I just don't fret over it.
 
Knowing the edge angle, is it beneficial?
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As you can see in the photo at this LINK>>>
I know and repeat the angles on these woodworking blades because the angles written on the blades are optimized for certain cantankerous wood species that I work the most. A couple of degrees shallower and the edge gets dinged up and chips out fibers in the surface of the wood and going steeper just takes more horse power to drive the edge through the wood.

The angles have been arrived at through trial and error.
The jig I use to sharpen them tends to lend it's self to more precise angle selection by the numbers.

When it comes to my pocket knives I do the same thing but totally ignore the numbers. Based on an average week or two of use at work if the edge is holding up well (which is usually the case) I thin out (reprofile) the behind the edge geometry to see if I can't make it a better slicer and make it just feel better while cutting. Almost to a knife this IMPROVES the performance immensely ! ! !
(the exception we will get to later)
From there if the edge gets rolled a bit or dinged I put a bit of a micro bevel on the edge to toughen it up a little. If it holds up well I may even thin it more in future sharpening.

How much just depends on my feel for the steel and the geometry that is there to work with.
Some times the factory edge can be a whopping 0.030 inch (thirty thou) thickness behind the edge and crazy angles like 22° per side.
If one looks at the Ankerson Rope cutting test the edges that were making all the others look silly were along the lines of 0.005 to 0.008 behind the edge and 15° per side.

15° is a pretty average angle per side for a fairly high performance edge for light EDC folder (and not so light). I tend to go even shallower but I'm careful with my knives.

How will YOU know when you are at that angle ?
Your knife will cut well don't worry about it.
Use your knife and experiment to determine WHAT WORKS BEST FOR YOU.

Use the sharpie method to tell if you are grinding metal off behind the edge or are ON THE EDGE just sharpening it and maintaining it OR are making the angle steeper.
With the latter the marker will remain on the sharpening bevel but the tiny line right at the edge will be coming off.

Edge Pro Apex . . . makes this easier to do consistently. I use the colored "angle lines" but don't try to decipher them in to actual numbers. They just let me have a reference to get in the ball park.

Now to the knife that was the exception that I didn't have to thin behind the edge or make the sharpening bevel angle shallower : I call it My Little Monster. It is a Japanese Kitchen knife with White Paper Steel. I've listed it's specs here in the past. I don't recall what they are off hand. Some where around 0.008" behind the edge and 10° or less per side sharpening angle.
Cutting just fruit and vegetables on a decent white plastic cutting board I got about twenty two months out of the edge before it stopped shaving hair. I recently updated that thread here.

YMMV
That's a good place to start IMO and if the blade shows damage steepen 'er up.
For instance I have a SAK Bantam (a little single blade slip joint) that I have put that kind of geometry on and use daily at work to cut soft fairly large diameter rubber tubing to leave a very precise square edge. To many people's chagrin the same knife cuts seriously good size wire ties better than any other knife I've seen or tried.
I'm just saying . . .

Murray says it all here :
 
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Kind of obvious, but since I don't see it mentioned: If you plan to touch up the knife on a honing rod setup and use the pre-drilled angles, you would need to be sharpening at or below those angles—same goes with sharpening more acutely than micro bevel.

Exactly how accurate on the angles? At least 3–5 degrees less, or to taste, for primary bevel.
 
Wowbagger said:
Edge Pro Apex . . . makes this easier to do consistently. I use the colored "angle lines" but don't try to decipher them in to actual numbers. They just let me have a reference to get in the ball park.
Click to expand...

Here is a short ( :) ) example from a sharpening session I did yesterday.
I sharpened My Little Monster on the Edge Pro Apex. The setting was near the shallowest angle colored line; the red one at the bottom of the vertical post.

I then decided to barely touch up my Kershaw Strobe. The knife still has its stock factory geometry and edge. The edge was still pretty sharp; they did a fine job at the factory of leaving an edge with no bur, no rolls, no dings and sharp enough to use.

I set the angle through trial and error having first put some dashes of magic marker right on the sharpening bevel from the factory. There was a rough grind from the factory to establish the edge then they had put on a fairly good size secondary bevel on at a steeper angle to refine the edge which was fairly polished and had taken off most of the coarse grind lines.

The line that the Edge Pro ended up being set at to allow me to get the stone onto the very edge was well above any colored line on the vertical post.

I look forward to thinning 'er out and making the sharpening angle more within the parameters of reality . . . er . . . I mean an angle that I like to use.
 
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I use a harbor freight 1x30 belt grinder with an angle guide to reprofile. Taking a 40 degree to 25 degree inclusive is done very quickly. Then I use a paper wheel or just finish freehanding it, following the new geometry. If I want to change something I do so with the belt.
 
3fifty7 said:
I don’t think it’s worth that $300 for that product, that you are advertising?!?!?!
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Aaaaah Crap !
That's what I get for not reading further down
I was just typing merrily away like we were helping some one.
Oh well maybe some young person lurking read it and will bang their head a little less on the wall than I did.
 
Hey if anyone's computer slows down from my link to the PhotoBucket photo of my hand plane blades go in and delete the cookie to PhotoBucket. I had to delete it like five times to get rid of the nasty thing.
At least I think that was why my computer turned into a stump.
It's fine now. I deleted a bunch of others while I was there.
it's just that it reminds me of the old days a year or so ago of ATTEMPTING to use photobucket here.
 
You can approximate edge angles all you want, but there's a reason recipes use measured ingredients and experiments use measured reagents, etc.: So that you can repeat them reliably with the same result and so that others can use them to get the same result; as well as being able to make slight changes and check the effects. It's impossible to communicate "right about like so" to anyone who's not in your physical presence, and even then they probably won't get it right.
 
Exactly. The numerical values are the target you're trying to hit. Fortunately even if you don't get a bullseye you're usually able to hit the target as a whole, and that's close enough in most circumstances. But if you don't even know where the target is, it can be much more challenging to hit. :D
 
I used to use guided setups (Lansky, Gatco, DMT Aligner) to sharpen my knives and always set them as low as possible, just to get as much out of them as I could. The one thing that taught me, eventually, is that anything at or below ~ 30° inclusive usually satisfied my expectations for how I use my knives. I also learned that virtually any knife with a decent heat treat will hold up reasonably well at ~ 30° inclusive at least, if not a little bit lower.

Since I started freehand-sharpening, I've found that my natural hold on the knife always seems to get the edge in the ~ 25-30° inclusive ballpark, which is ideal for me. Beyond that, I generally have no further interest in actually knowing in exact terms what the given angle is, if I already know I'm happy with how the geometry is working for me. If it's not quite cutting as well as I'd like, I'll just 'take it a little thinner' at resharpening time. On the flipside of that, if I notice the edge is a little too vulnerable to damage in my normal uses, I'll start adding a microbevel (30° inclusive or lower) to bolster it a little bit. But again, I don't think too much about what the finished angle is, so long as I know it's holding up better.

I occasionally use V-crock setups for quick touch-ups. A couple of them allow sharpening down to at least 30° inclusive with their factory bases. I've since made a couple of my own bases for the rods, drilling the holes at 25° inclusive in them. In using any of these, I'm at least able to confirm if/when my edges are within that 25-30° ballpark, if I don't have to tilt/incline the spine of the blade a little bit in using them.
 
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I don't believe you need that kind of equipment to sharpen any knife... If someone brings me a slicing cooking knife whatever edge on there it's going back to 18-20dps, if you give me a boning knife it's 22-24dps. Regardless of the current edge it may have. I do Hunting Knives between 24-30dps depending on steel and fillet knives from 10-16dps also. I just need a good protractor device to setup the jig. There are some exception sometimes with super high end Japanese blades but it's rare for me to encounter those. I would say... A Sharpie marker: 99¢ :D
 
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