How do I know at exactly what angle to hold my specific knife to sharpen it? I don't mean blade x stone length angle, but rather how high up the spine is up from the stone? In some videos by JKI, I see Jon almost putting a double bevel knife completely flat on the stone, while others it's at a higher angle, maybe about 10-20 degrees. I understand microbevels are sharpened at higher angles, but I am only asking about regular sharpening.
Question on sharpening angle
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First of all, @Chef Doom bwahahahahaha
Now back to the question, a safe bet range for Japanese knives is somewhere in the 10-15 degree per side range. Towards the 15 or even higher side of things, the knife will feel less sharp, but be more durable. Nearer to the 10 degree range or even lower, the knife will feel sharper but be more fragile/brittle. Find something that works for you.
Now back to the question, a safe bet range for Japanese knives is somewhere in the 10-15 degree per side range. Towards the 15 or even higher side of things, the knife will feel less sharp, but be more durable. Nearer to the 10 degree range or even lower, the knife will feel sharper but be more fragile/brittle. Find something that works for you.
FWIW, as a guide, if you raise the (midline of the) spine a half of the knife's height off the stone, you have made a 30 degree (*) angle.
A third gives about 19.5* (close enough to 20*)
A quarter gives about 14.5* (close enough to 15*)
A fifth gives about 11.5* (close enough to 12*)
A sixth gives about 9.5* (close enough to 10*)
A seventh gives about 8*
A third gives about 19.5* (close enough to 20*)
A quarter gives about 14.5* (close enough to 15*)
A fifth gives about 11.5* (close enough to 12*)
A sixth gives about 9.5* (close enough to 10*)
A seventh gives about 8*
HRC_64
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SAT question
If you assume the average 240mm knife is 50mm tall,
what does all that translate into...
(for MM off the stone for the spine)?
Is SAT some kind of high school exam?SAT question
If you assume the average 240mm knife is 50mm tall,
what does all that translate into...
(for MM off the stone for the spine)?
I really just use this calculation to help me eyeball the angle. In the end, it's the TLAR technique.
HRC_64
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old uni placement exams in the US
(had a distinctive, somewhat annoying
way of asking math problems)
was just kind of joking, in other words
Ahhh... got it [emoji1]
Paraffin
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Here's how I think of it, for what it's worth. It's easy to eyeball a 45 degree angle to the stone: Start at 90 degrees, drop the spine of the knife to half that angle. From that 45 degree estimated angle, drop the spine of the knife to half that angle again, and you're at roughly 22.5 degrees. I use that angle for sharpening beater knives, bone cleaver, soft stainless like old Wusthofs, etc.
From that estimated 22.5 degree angle, drop the spine of the knife one more time to an estimated half that angle, and you're at roughly (very roughly) 11 degrees. I use this angle for sharpening Japanese knives.
After the eyeball estimate for angle, it's just training your dominant hand to hold that angle consistently while pushing and pulling across the stone with your other hand. Keeping the angle consistent so you're not rounding the edge, is more important than hitting an exact angle, as long as you're in the ballpark for desired angle.
From that estimated 22.5 degree angle, drop the spine of the knife one more time to an estimated half that angle, and you're at roughly (very roughly) 11 degrees. I use this angle for sharpening Japanese knives.
After the eyeball estimate for angle, it's just training your dominant hand to hold that angle consistently while pushing and pulling across the stone with your other hand. Keeping the angle consistent so you're not rounding the edge, is more important than hitting an exact angle, as long as you're in the ballpark for desired angle.
SAT question
If you assume the average 240mm knife is 50mm tall,
what does all that translate into...
(for MM off the stone for the spine)?
see attached for angles for blade width vs height of spine above stone.
Attachments
Trig aside, had a pretty smart fellow tell me once that a consistent angle was much more important than an absolute angle. Guy sharpened knives in his PJs
Corradobrit1
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There are some very nifty protractor apps for cell phones. Rest phone on blade to get precise angle and memorize. Simples
I agree with Dave. Consistency over absolute angle is key
I agree with Dave. Consistency over absolute angle is key
Kippington
A small green parrot
That's it boys. The secret to perfect sharpening is out, cat's out of the bag... shut her down.Guy sharpened knives in his PJs
thisTrig aside, had a pretty smart fellow tell me once that a consistent angle was much more important than an absolute angle. Guy sharpened knives in his PJs
Corradobrit1
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Will shorts do? I don't wear PJ's but i want a world beating edge?
Yes.
However, since during the day I’m a mathematician, I can’t stop myself from including the formula in this thread, no matter how hard I try.
(height of the spine off the stone) = (height of knife) sin(desired angle).
E.g. if you have a 50mm knife and you want a 12 degree angle, enter the text “50 sin(12 degrees)” into google search and out pops the height you need to have the spine.
Ok, now I feel better.
Glad we could help [emoji6]
