Question about different types of edges

[basb]

I am practicing convex sharpening. Using sandpaper on 6mm Armafelx insulation.
I grabbed an old Victorinox kitchen knife and began.

It took me a while. Beginning with 280 grit and than 400 grit. Its now near Space-time slicing sharp and slices paper like i have never achieved before.
However it does not shave.
On my work i freehanded my ESEE Izula on a sharpening stone. My guess is a medium stone.
After awhile it had a pretty nasty bite and it shaves almost clean. However it does not slice paper like the kitchen knife does, not even close.
The Izula is still full flat V-grind
Both are sharp, thats for sure. But i never thought they'd work different. Is the difference in sharpness due to the edge type or am doing things wrong?

 

[Obsessed with Edges]

There might be a wire edge there. Depending upon which way it 'leans' (to one side of the edge or the other), you could often see results like this. Usually, unless the wire edge is completely folded over, it'll still cut through paper. And with shaving, if the wire edge is angled slightly down towards the skin & the base of the hair, it can shave. If the wire edged is curled upward in the other direction, it might not shave so well (if at all). This could be resolved by carefully stropping the edge. If the wire edge is stubborn, you might cut into a piece of wood (as if whittling) or a piece of thick, stiff leather. This usually helps to align or break off the wire edge. Afterwards, strop it and test it again.

Also, if an edge is highly polished, oftentimes it'll shave great (which is essentially a 'push cut'; polished edges do this well), but won't necessarily slice paper as well (which often works better with a somewhat toothy edge). Some steels will behave like this. It apparently has a lot to do with the relative size and/or shape of the carbides present in that particular steel. But, even this can be overcome. The more you refine & thin the edge, the better it'll perform, to a point where you can 'push cut' through the paper (that's when you know it's getting REALLY sharp; definitely a good sign ).

 

[Jason B.]

Your backing is too thick.

The izula does not slice as well because it is a thicker flat grind.

You need to go to higher grits like 600, 800, 1000, and 2000, then your knife will be really sharp.

 

[basb]

So i will need to refine the izula edge? I can understand that.
But i still don not realy understand why the victorinox edge does not shave..... Everything else it slices great.
On both blades i have not found burr or wire edge.

 

[singularity35]

try working the finer grits, maybe you just need a more polished edge to shave. work up to at least 1500 grit.

 

[Obsessed with Edges]

So i will need to refine the izula edge? I can understand that.
But i still don not realy understand why the victorinox edge does not shave..... Everything else it slices great.
On both blades i have not found burr or wire edge.

If you've convexed the edge on the Vic kitchen knife, I wouldn't be surprised if it's a bit too rounded. Probably has some toothiness to it, which would explain why it slices paper (paper's not that hard to cut with a knife anyway). If it's like most kitchen/chef's knives, I'm assuming the blade was quite thin to begin with. The vast majority of kitchen knives are made with V edges (or acutely bevelled on one side), and I think it's for good reason. A thin blade cuts better that way. And razor blades, made exclusively for shaving, aren't convexed either. Again, for good reason.

 

[basb]

If you've convexed the edge on the Vic kitchen knife, I wouldn't be surprised if it's a bit too rounded. Probably has some toothiness to it, which would explain why it slices paper (paper's not that hard to cut with a knife anyway). If it's like most kitchen/chef's knives, I'm assuming the blade was quite thin to begin with. The vast majority of kitchen knives are made with V edges (or acutely bevelled on one side), and I think it's for good reason. A thin blade cuts better that way. And razor blades, made exclusively for shaving, aren't convexed either. Again, for good reason.

The convexing is more for practicing reason than real usefulness.
I got some good sandpaper(3M Wetordry) instead of the lowbudget stuff. Got started on 600, than 1000 and finished with 1200 grit.
The bevel is now shiny It slices radices and tomatoes like crazy now and it shaves but not impressive but thats what you just explained.
One side however isnt shiny and has some scratches. That would just be human error. I like how the edge turned out as a first attempt to convex a V-grind.
The edge wont last long on such a thin knife but i dont care

 

[Obsessed with Edges]

The convexing is more for practicing reason than real usefulness.
I got some good sandpaper(3M Wetordry) instead of the lowbudget stuff. Got started on 600, than 1000 and finished with 1200 grit.
The bevel is now shiny It slices radices and tomatoes like crazy now and it shaves but not impressive but thats what you just explained.
One side however isnt shiny and has some scratches. That would just be human error. I like how the edge turned out as a first attempt to convex a V-grind.
The edge wont last long on such a thin knife but i dont care

Sounds like you're making progress & learning some new things as you go. That's what it's all about, just keep at it. As long as you're getting at least a little bit better with each step, you know you're headed in a more enlightened direction. Good work! :thumbup:

 

[basb]

Was gonna start a new topic but it fits in here as well.
Another question;

I have a new BRKT bravo 1 though it was pretty sharp when it arrived i used some 1200 grit sandpaper and stropped it afterwards.
Its now sharp enough to pop hairs of my arm, make very, very thin paper curls and push cut clean through paracord. I tried to slice a tomato but its actually hard.... I have to use pressure to slice through the skin. If i 'attack' a tomato slice form the side it slices through with ease.
I have stropped the daylights out of it but it doesn't change
Is this due to the .21 inch thick blade or is it the polished edge?

When stropping the edge is about 5mm(1/5th inch) of the leather in order to contact the edge and hear a faint abrasive sound. Closer and im not touching it.
Its not that it will be used as a food slicer, more a woods knife. But it boggles my mind....

 

[Obsessed with Edges]

Was gonna start a new topic but it fits in here as well.
Another question;

I have a new BRKT bravo 1 though it was pretty sharp when it arrived i used some 1200 grit sandpaper and stropped it afterwards.
Its now sharp enough to pop hairs of my arm, make very, very thin paper curls and push cut clean through paracord. I tried to slice a tomato but its actually hard.... I have to use pressure to slice through the skin. If i 'attack' a tomato slice form the side it slices through with ease.
I have stropped the daylights out of it but it doesn't change
Is this due to the .21 inch thick blade or is it the polished edge?

When stropping the edge is about 5mm(1/5th inch) of the leather in order to contact the edge and hear a faint abrasive sound. Closer and im not touching it.
Its not that it will be used as a food slicer, more a woods knife. But it boggles my mind....

I'm betting it's a combination of the two (thick blade AND polished edge). I think most people would ideally prefer a THIN blade with a slightly toothy edge for slicing tomatos & other veggies. There's somewhat of a trade-off too, between the two characteristics. A highly polished edge on a thin blade would work OK too (even VERY well if the edge is highly refined), or a slightly toothy edge on a thicker blade should also handle the task fairly well.

 

[basb]

I tried the vic kitchen knife which i stropped too yesterday and doesnt realy slice as it did before stropping.
Thansk for the info, very informative

 

[Obsessed with Edges]

I tried the vic kitchen knife which i stropped too yesterday and doesnt realy slice as it did before stropping.
Thansk for the info, very informative

The tomato test is kind of a classic for a lot of knife-sharpening nuts like us. I'm still experimenting with it. I like very acute and highly polished edge bevels. But I have noticed that more polish doesn't necessarily mean better slicing, especially on something slick & flexible like tomato skin. Most of the commercially available 'tomato knives' you find nowadays come with a serrated blade, because it's more forgiving for that task. The edge itself doesn't necessarily have to be as sharp or refined, because the 'teeth' are doing most of the work.

Some folks like to highly polish the bevel, then lift the angle just a degree or two, to make one or two VERY LIGHT passes on a coarser grit. That puts some of the 'bite' back into the edge.