47 replies to this topic

[violins88]

I cannot imagine how people sharpen a knife with a curved edge without a jig. I know some, or perhaps most, of the best violin makers use a curved edge. Here is a simple method I worked out. I have a 6000 grit flat wetstone grinder. I inserted a PVC pipe in the tool rest. A notch in the tool rest. See it here. Apologies for the low quality photography.

[fiddlecollector]

Hi John, Clever and interesting! Glad you perservered with the O1 ,its a great steel if treated properly.Your heat treatment sounds interesting
Bob

[violins88]

Hi John, Clever and interesting! Glad you perservered with the O1 ,its a great steel if treated properly.Your heat treatment sounds interesting
Bob

Thanks. People heat treat with a torch. But after doing lots of reading about steel, particularly O1, I built a kiln with very good temperature control, and an oil bath with good temp. control. It seems I have found a good recipe. I am getting very positive feedback from violin makers.

I think you CAN harden with a torch, but I think the results are far from optimum.

I would like to hear from others who sharpen curved edges. How do you do it?

BTW, my method should work on a Tormek, although I have not tried it, since I don't have a the big T machine.

[Janito]

I would like to hear from others who sharpen curved edges. How do you do it?

From [a Diary of] a Nobody - I use a curved action of the hand/arm to move the blade on the flat surface.

Works fine for me.

[Andrew Kochie]

These knives are incredibly good. I dont use my japanese damascus steel knives anymore and switched to these. I'm spending much less time sharpening and more time getting work done. Ive seen sketchy results from oil tempering steel in the past leaving the steel too brittle, or inconsistent hardness which could be felt over time. Whatever method John is using is very consistent.

After using these for a few weeks now I can see why Sam Z and Collin liked these knives. Good stuff.

[Oded Kishony]

I wonder what they intend to do with 21 knives, a circus act ;-) ????

congrats John on your breakthrough discovery !


Oded

[violins88]

I wonder what they intend to do with 21 knives, a circus act ;-) ????

congrats John on your breakthrough discovery !


Oded

Andrew,
Thanks for the compliment.

Oded, I imagine they plan on using some of them as gifts. And also, from talking with Collin, I got the impression they plan to use these knives a lot, and for a long time, until they get too short. He wanted the whole blade hardened. Also, there were 4 widths of knives, 9 mm, 12 mm, 16 mm and 19 mm. So that's about 6 of each type.

BTW, they showed them at Oberlin and took orders, which I totally appreciate.

[saintjohnbarleycorn]

Congrats, glad you found a good process and are being successful at it after all the experimentaion

[violins88]

Congrats, glad you found a good process and are being successful at it after all the experimentaion

Thanks,

Yes, it is gratifying. Now my worry is quality control. It only takes one bad blade to initiate a whole lot of negative comments.

Janito,
We need more nobody's like you.

[MikeC]

It is easy to sharpen a curved blade. All it takes is a sharpening stone / hone and a little hand eye coordination. Why make things so complicated?

[violins88]

It is easy to sharpen a curved blade. All it takes is a sharpening stone / hone and a little hand eye coordination. Why make things so complicated?

Mike,

I guess I am lacking in coordination and training.

[MikeC]

Most pocket knife have some curve in the blade so practice on a cheap one. There are lots of sharpening videos so I just picked this one. As you push the blade along the stone you swing it around to follow the curve and at the same time lifting the back of the knife as you get into the curve and into the point, that keeps the edge angle uniform. It just takes a little practice. I've had a knife in my pocket since about 6 years old so it tends to come natural I suppose.
Practice with a spay blade, now that's a curve!

[fiddlecollector]

Theres nothing wrong with Johns sharpening jig,cheap to make and useful .If he is selling them he needs to reproduce things accurately .
Hand sharpening is fine but its not totally accurate or perfectly repeatable,but useful to learn for your own tools.
If you want more expensive you could try this Wicked edge

[violins88]

Most pocket knife have some curve in the blade so practice on a cheap one. There are lots of sharpening videos so I just picked this one. As you push the blade along the stone you swing it around to follow the curve and at the same time lifting the back of the knife as you get into the curve and into the point, that keeps the edge angle uniform. It just takes a little practice. I've had a knife in my pocket since about 6 years old so it tends to come natural I suppose.
Practice with a spay blade, now that's a curve!

Mike,
Thanks for trying to help me out. I watched the video. I am really much too compulsive about accuracy in holding the blade angle. For me, I need a method which is more rigid in holding the correct angle.

[lyndon]

the main advantage to hand grinding, is you can have a much larger selection of quality grind stones to choose from than you might on a grinding wheel, plus you never have to change grinding wheels

for instance i have one antique arkansas stone i use for my finest work, i cant imagine in a million years finding a grinding wheel of that quality

[violins88]

the main advantage to hand grinding, is you can have a much larger selection of quality grind stones to choose from than you might on a grinding wheel, plus you never have to change grinding wheels

for instance i have one antique arkansas stone i use for my finest work, i cant imagine in a million years finding a grinding wheel of that quality

Lyndon,
The other thing to note is that I can imagine using the back bevel shoulder as a guide. I CAN envision that method working for me. Also, even though my Makita stone is supposed to be 6000 grit, it moves very fast and I think slowing it down would give me a better final strop. The wheel turns maybe at 180 rpm. This is a Delta grinder, an old one. My use of the vise grip is probably transferable to the Tormek. I don't know.

I concede that trained violin makers can sharpen by hand. I am not trained. Maybe in my next life.

[bmccarthy]

Here's a photo of one of Han's Nebel's knives. . . . .again!! . He hollow grinds on an 80grit 6" fast bench grinder then sharpens on japanese water stone's. With a bit of practice you can keep the edge in contact with the flat stone using the hollow. I've tried using the Tormek but the diameter is too big leaving too small a hollow making it difficult to keep the edge in constant contact with the flat stones. However, I find the Tormek very useful for quickly grinding of the shape of the blade.

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[violins88]

Here's a photo of one of Han's Nebel's knives. . . . .again!! . He hollow grinds on an 80grit 6" fast bench grinder then sharpens on japanese water stone's. With a bit of practice you can keep the edge in contact with the flat stone using the hollow. I've tried using the Tormek but the diameter is too big leaving too small a hollow making it difficult to keep the edge in constant contact with the flat stones. However, I find the Tormek very useful for quickly grinding of the shape of the blade.

Brian,
If the blade comes out of the handle, I recommend you try the vise grip idea on the Tormek. If you want a larger radius of curvature on the edge, just make some kind of extension for the 6 inch vise grip. I grind blades that are long and thin like this on my belt grinder wheel. Works great.

[Jeff White]

Here's a photo of one of Han's Nebel's knives. . . . .again!! . He hollow grinds on an 80grit 6" fast bench grinder then sharpens on japanese water stone's. With a bit of practice you can keep the edge in contact with the flat stone using the hollow. I've tried using the Tormek but the diameter is too big leaving too small a hollow making it difficult to keep the edge in constant contact with the flat stones. However, I find the Tormek very useful for quickly grinding of the shape of the blade.

Hans just used my main knife (curved blade)in a sharpening demo at a workshop a few weeks ago. He still uses the way mentioned above. However, he flattened out my cure, but it is, wicked sharp. Interesting, watching him do this,likes to use his hand a pivot. I guess a human version of violins88's jig . jeff

[violins88]

Hans just used my main knife (curved blade)in a sharpening demo at a workshop a few weeks ago. He still uses the way mentioned above. However, he flattened out my cure, but it is, wicked sharp. Interesting, watching him do this,likes to use his hand a pivot. I guess a human version of violins88's jig . jeff

Jeff,
If you want to use stationary stones, you could clamp on the vise grip and then install a post in your work bench to receive the pivot end of the vise grips. I am confident the geometry works out. I guess I (or someone) need to engineer an aesthetically pleasing vise grip. Actually I hate the look and feel of the vise grip for this process, and it needs to be much lighter, even though it does the job. The mass of the grip reduces the ability to feel what's going on with the edge.