My edge angle changes depending on blade steel, stock thickness and intended use of knife, with something like K390 or CPM M4 I drop the angle to 15, 30 inclusive, something like CPM 20CV generally 17 to 20 degrees, additionally I will change edge finish dependent on steel, D2 finish edge with 400 grit, CPM S30V 600 to 800, CTS XHP 2000 and strop all, I make it complicated
The steel & purpose determines the angle for me. Higher wearing steel like 20cv gets reprofiled to 30-34 inclusive. Softer steel gets 36-50 depending on how hard I'm going to use it.
Fixed blades for outdoors use, are great somewhere close to 20 per side. Go for 21 per side or 42 inclusive. if you want to improve edge stability ( slightly convexing will provide way more stability though! ) 19 per side if your steel and it's heat treatment, provide good edge stability. So, it all depends on the type of the knife and the kind of use the knife is going to see.
Good information and I set up a spreadsheet to do the calculations, but all of the tutorials miss one thing. When you have multiple facets you have a primary facet starting at the back of the knife, then you may have a secondary facet, then the cutting edge angle facet. Two faceted knives with just a primary and the cutting edge facet is straight forward, but when you have a facet in between and you are clamping on to the primary facet, the formula does not account for the secondary angle between the primary and the cutting facet. In other words, when you set up the jig you clamp to the primary facet to grind the cutting facet. If there is another angle between the two facets, you will be grinding the cutting facet using the sum of the two facet angles. Have you devised a method to calculate the second facet and subtract the cutting facet angle? I am going to work it out, it will take a little more math, but the nice thing about spreadsheets is once you figure it out you have it forever. I have many formulas I have saved over the years that I use often
May a bit easier way to estimate knife edge angel. Measure the thickness of the blade behind the cutting edge. - If that equals the length of the bevel you have a 30º angle bevel. - If the length of the bevel is 2 times the thickness you have a 15º angle/bevel.
Wish it was more detailed. Newer to knives, how do you measure "behind the bevel"? That small part of the edge that's different from the rest? Inches or mm? Assuming inches but should be more clear.
Clarification, please: measuring behind the edge bevel…it looked like the caliper was cocked a little. You’re trying to keep a right angle (caliper to blade), correct? Thanks for a helpful video.
good lesson, but i still will use a sharpie and a digital angle finder, and test if all the marker comes off, I am not comfortable using just math in sharpening
I love seeing this useful application of trigonometry. As a novice freehand sharpener, this will be extremely useful for me; thanks!
I'm not a math guy, but your video was very understandable... Well done!
Great, so simple yet so easy to miss that you can do. Thanks!
Nicely done!
My edge angle changes depending on blade steel, stock thickness and intended use of knife, with something like K390 or CPM M4 I drop the angle to 15, 30 inclusive, something like CPM 20CV generally 17 to 20 degrees, additionally I will change edge finish dependent on steel, D2 finish edge with 400 grit, CPM S30V 600 to 800, CTS XHP 2000 and strop all, I make it complicated
The steel & purpose determines the angle for me. Higher wearing steel like 20cv gets reprofiled to 30-34 inclusive. Softer steel gets 36-50 depending on how hard I'm going to use it.
Fixed blades for outdoors use, are great somewhere close to 20 per side. Go for 21 per side or 42 inclusive. if you want to improve edge stability ( slightly convexing will provide way more stability though! ) 19 per side if your steel and it's heat treatment, provide good edge stability. So, it all depends on the type of the knife and the kind of use the knife is going to see.
Good information and I set up a spreadsheet to do the calculations, but all of the tutorials miss one thing.
When you have multiple facets you have a primary facet starting at the back of the knife, then you may have a secondary facet, then the cutting edge angle facet.
Two faceted knives with just a primary and the cutting edge facet is straight forward, but when you have a facet in between and you are clamping on to the primary facet, the formula does not account for the secondary angle between the primary and the cutting facet.
In other words, when you set up the jig you clamp to the primary facet to grind the cutting facet. If there is another angle between the two facets, you will be grinding the cutting facet using the sum of the two facet angles. Have you devised a method to calculate the second facet and subtract the cutting facet angle?
I am going to work it out, it will take a little more math, but the nice thing about spreadsheets is once you figure it out you have it forever. I have many formulas I have saved over the years that I use often
May a bit easier way to estimate knife edge angel. Measure the thickness of the blade behind the cutting edge.
- If that equals the length of the bevel you have a 30º angle bevel.
- If the length of the bevel is 2 times the thickness you have a 15º angle/bevel.
No wonder I never used trigonometry, just an old sharpie, great information though 👍 👏 👌
By 2:08, I realized I need to send my sewing shears out to a professional for sharpening. This is NOT a DIY project for the average schmoe. :-)
Trig or treat! Thanx.
Very cool!
Wish it was more detailed. Newer to knives, how do you measure "behind the bevel"? That small part of the edge that's different from the rest? Inches or mm? Assuming inches but should be more clear.
See I did the inverse and s-1 on degrees and it pops sin-1 in the problem what's happening how do I fix it?
Second example is 14.57 or 29.14
Everything else I do agree
gradiant or degree?
Wonderful video. Make sure your calc is set to degrees and not Rad. The deg/rad button is on the lower left on an iPhone. This does not work on rad.
Has anyone tested this on a fixed angle sharpener? That Para 3 didn’t look 15 to me
I was wondering the exact same thing
Actually, on the first example angle is 12.77 or 25.54 included
S.B. like this: Inverse TANGENT of 0.0925/0.408 not Inverse SINE
Saved the video just in case
Get it the way you need it , I like an edge that'll make a easy cut .....or quick work to feed my hogs a pado or two .
Wow, An actual real world use for trigonometry.... who knew. 😀
Shouldn’t you be using the inverse tangent function? You are not using the hypotenuse but the opposite and adjacent side lengths.
He is measuring the hypotenuse
Clarification, please: measuring behind the edge bevel…it looked like the caliper was cocked a little. You’re trying to keep a right angle (caliper to blade), correct? Thanks for a helpful video.
good lesson, but i still will use a sharpie and a digital angle finder, and test if all the marker comes off, I am not comfortable using just math in sharpening
Is the digital angle 📐 finder you are referring to the one that looks like a protractor hinge ? Thanks