Edge angle and polish stones

[Jeeeen!]

I got a question about edge angles.
My shirogorov has a really small bevel. I want to sharpen them to be a little wider. Will this improve performance at all? Or stick with factory angle?

Also, I notice the higher grit I go, the less it feels sharp when I do the sticky finger test.
Is this a result of dulling my edge on a 2000 or 5000 grit stone?
It'll bite my fingernail really good at 800 grit but gets slippery on higher grits, which confuses me.

I'm using a KME system.

 

[Jeeeen!]

Bump

 

[Obsessed with Edges]

In general terms, widening the bevels implies sharpening at a lower edge angle. That should always improve cutting performance within limits, i.e., if the angle doesn't get too low for the steel to remain strong at the edge. Almost any decent cutlery steel can handle edge angles down to 25°-30° inclusive (12.5°-15° per side) in normal, non-abusive cutting tasks.

Also in general terms, going higher in polish will reduce the toothy bite in an edge, which is usually why the edge will feel 'slicker' or less 'sticky' on fingertips or nails. But there's also a risk of rounding over the apex with more polishing, depending on how it's done. If it's done on stropping media with a compressible backing, that rounding tendency will be more of an issue. If the apex gets rounded over, the edge will also feel more 'slippery' and won't cut nearly as well. So, with higher polish, you also need to make sure the apex stays very, very crisp as you go. Polishing also implies the apex will become thinner as you progress. And with some steels, going too thin at the apex will also weaken it and make it prone to rolling or flattening in use. Some steels with very fine grain and high hardness take a highly polished edge very well. And others, with less-fine grain or lower hardness don't respond as well to polishing, with the edge becoming too weak or unstable at high polish.

 

[SwissHeritageCo]

In general terms, widening the bevels implies sharpening at a lower edge angle. That should always improve cutting performance within limits, i.e., if the angle doesn't get too low for the steel to remain strong at the edge. Almost any decent cutlery steel can handle edge angles down to 25°-30° inclusive (12.5°-15° per side) in normal, non-abusive cutting tasks.

Also in general terms, going higher in polish will reduce the toothy bite in an edge, which is usually why the edge will feel 'slicker' or less 'sticky' on fingertips or nails. But there's also a risk of rounding over the apex with more polishing, depending on how it's done. If it's done on stropping media with a compressible backing, that rounding tendency will be more of an issue. If the apex gets rounded over, the edge will also feel more 'slippery' and won't cut nearly as well. So, with higher polish, you also need to make sure the apex stays very, very crisp as you go. Polishing also implies the apex will become thinner as you progress. And with some steels, going too thin at the apex will also weaken it and make it prone to rolling or flattening in use. Some steels with very fine grain and high hardness take a highly polished edge very well. And others, with less-fine grain or lower hardness don't respond as well to polishing, with the edge becoming too weak or unstable at high polish.

Great post.

 

[Greggy]

I have mid-tier steels almost exclusively (9Cr, AR RPM9, 440C, VG10, D2 etc.). In my experience with these steels, the only way to avoid dulling the edge with a 6000 grit stone is to adjust very carefully downward pressure on the blade. I go very very light and typically do not dull the edge. But sometimes there is no avoiding this even with minimal pressure (especially the case with my D2 steels). I have almost found my 6000 stone to be useless. I can get razor sharp with my 1000.

 

[UncleBoots]

I have mid-tier steels almost exclusively (9Cr, AR RPM9, 440C, VG10, D2 etc.). In my experience with these steels, the only way to avoid dulling the edge with a 6000 grit stone is to adjust very carefully downward pressure on the blade. I go very very light and typically do not dull the edge. But sometimes there is no avoiding this even with minimal pressure (especially the case with my D2 steels). I have almost found my 6000 stone to be useless. I can get razor sharp with my 1000.

That sounds a bit odd, although very low pressure during the finishing stages of sharpening is desirable and normal. What 6000 stone are you using?

 

[Greggy]

That sounds a bit odd, although very low pressure during the finishing stages of sharpening is desirable and normal. What 6000 stone are you using?

My 6000 is a Sharp Pebble. I am considering a Norton to replace it.
BTW, the dulling effect of higher grit stones is a common comment here. I know because having experienced the same, I pay attention to such comments. Because I only own mid-tier steels, I "assume" that this is a phenomenon with those steels, although not all of them.

 

[Jeeeen!]

In general terms, widening the bevels implies sharpening at a lower edge angle. That should always improve cutting performance within limits, i.e., if the angle doesn't get too low for the steel to remain strong at the edge. Almost any decent cutlery steel can handle edge angles down to 25°-30° inclusive (12.5°-15° per side) in normal, non-abusive cutting tasks.

Also in general terms, going higher in polish will reduce the toothy bite in an edge, which is usually why the edge will feel 'slicker' or less 'sticky' on fingertips or nails. But there's also a risk of rounding over the apex with more polishing, depending on how it's done. If it's done on stropping media with a compressible backing, that rounding tendency will be more of an issue. If the apex gets rounded over, the edge will also feel more 'slippery' and won't cut nearly as well. So, with higher polish, you also need to make sure the apex stays very, very crisp as you go. Polishing also implies the apex will become thinner as you progress. And with some steels, going too thin at the apex will also weaken it and make it prone to rolling or flattening in use. Some steels with very fine grain and high hardness take a highly polished edge very well. And others, with less-fine grain or lower hardness don't respond as well to polishing, with the edge becoming too weak or unstable at high polish.

Thank you for your reply.

I'm using chosera stones. 320 500 800 1500 2000 5000.
The knife in question is a shirogorov with m390. This my first knife in this steel, so trying to figure out what angle and what grit is best.

I get burr on both sides on the lower grits, but lose that burr on the higher grits, I feel like I'd have to spend the entire day on the higher grits.

 

[Obsessed with Edges]

Thank you for your reply.

I'm using chosera stones. 320 500 800 1500 2000 5000.
The knife in question is a shirogorov with m390. This my first knife in this steel, so trying to figure out what angle and what grit is best.

I get burr on both sides on the lower grits, but lose that burr on the higher grits, I feel like I'd have to spend the entire day on the higher grits.

A common recommendation from waterstone experts is to use edge-trailing strokes only in refining steps, due to the tendency of the edge to be dulled by the slurry from the stone if using edge-leading or back & forth passes. More so, if using softer stones in the same stages. Many comment also about the same slurry effect being useful for deburring at the high-grit, refining stage. So, with waterstones, there's a fine line (apparently) between effective deburring and dulling the edge at the higher-grit stages.

I don't use waterstones myself, and haven't tried them. But that might be something to consider, if you're not already doing that.

 

[777 Edge]

Thank you for your reply.

I'm using chosera stones. 320 500 800 1500 2000 5000.
The knife in question is a shirogorov with m390. This my first knife in this steel, so trying to figure out what angle and what grit is best.

I get burr on both sides on the lower grits, but lose that burr on the higher grits, I feel like I'd have to spend the entire day on the higher grits.

I haven't personally tried my Chosera stones on M390 steel, I would normally use diamond resin stones for a steel like M390 due to the relatively higher amount of vanadium + chromium carbides in M390.

With M390, you might be getting into the territory of where Aluminum oxide stones such as the Chosera series is not the best option for finer grit polishing. Low grit, aluminum oxide stones generally work ok on most steels but higher grit lags in performance with many vanadium carbide steels.

 

[Blade Lab]

Agree with 777 Edge. You can get M390 sharp with aluminum oxide, but edge retention will suffer. The reason for this, I'm told, is that aluminum oxide is softer than vanadium carbides, so what you're doing is essentially sharpening the non-carbide steel matrix around the carbides and smoothing out the carbides themselves instead of fracturing them. OTOH, I think that using aluminum oxide as a final step (honing) can achieve very good keenness by exposing the carbides.

 

[Ourorboros]

Thank you for your reply.

I'm using chosera stones. 320 500 800 1500 2000 5000.
The knife in question is a shirogorov with m390. This my first knife in this steel, so trying to figure out what angle and what grit is best.

Chosera/Naniwa Pro doesn't come in 320, 500, or 1500.
Shapton Pro has a 320 and1500
Shapton Glass has a 320 and 500
But Shapton has no 800
All three have 2000 & 5000, though it should be said that Chosera is about 50% finer than Shapton.

Also your line-up is very crowded, unless you are trying to polish out scratches from thinning, for instance. In particular a 320-500-800 progression is just to small to be useful. Same with 1500-2000.
On kitchen knives I often go 500-2000-???. For EDC, 500->strop is useful.
With hard waterstones like this, slurry isn't much of a factor unless you used a nagura to create a slurry or you have sharpened that many knives/removed that much steel. Chosera and Shapton are notably the hardest water stones with the least slurry. You'll get different results on King (not Neo) and Suehiro.

 

[Ourorboros]

With a soft stone, you are not only contending with slurry, but the fact that you can cut into the stone itself, dulling your blade. If you have slightly too high an angle and don't have the feel, you might not notice this.
Soft stones do have a place, especially with different pressures, but you need to be aware.

 

[Jeeeen!]

It's starting to get a better bite when I push only. Maybe it was dulling on the pulls.

 

[kane22]

Some steels work well at lower grits...toothier edge. You can finish on an 800 grit stone, strop it and see how it works for you.

 

[Jeeeen!]

Some steels work well at lower grits...toothier edge. You can finish on an 800 grit stone, strop it and see how it works for you.

Ah I see.
Typically, what do people with m390 by shirogorov finish at?
The factory edge looked quite polished.

My chef knives, which were blue carbon, were toothy all the way to 8000 grit. I was a sushi chef.

 

[kane22]

I don't know that there is any one right answer. All M390 may not react the same depending on the heat treat, or any other steel for that matter. You might find one finish gives you a longer working edge, but might not be as super scary sharp to start with. Also the grit ratings for different stones can be all over the place. Depending on the type, and country of origin.

A quick test you can do is see if it cuts into a grape with out putting any weight on it, or just slide across the skin. I've had knifes really sharp, but with no bite. For most uses that's not what I want.

I use diamond plates for almost everything now, normally up to 1500 grit (600 if you want more bite). Then finish with balsa wood strops with diamond emulsion 9,6,1 micron. That's my favorite combo at this point.

 

[UncleBoots]

1000 grit diamond edges, lightly deburred on a very high grit Shapton stone, work well for all of my pocketknives. Occasionally I am inspired by something about the steel to finish on 3000 grit diamond. Shirogorov M390 was one of those. The steel seemed like it would take that well, and it did.

 

[helobite]

A common recommendation from waterstone experts is to use edge-trailing strokes only in refining steps, due to the tendency of the edge to be dulled by the slurry from the stone if using edge-leading or back & forth passes. More so, if using softer stones in the same stages. Many comment also about the same slurry effect being useful for deburring at the high-grit, refining stage. So, with waterstones, there's a fine line (apparently) between effective deburring and dulling the edge at the higher-grit stages.

I don't use waterstones myself, and haven't tried them. But that might be something to consider, if you're not already doing that.

I do have waterstones, never liked them, I will have to try that edge trailing idea and see if it works. I free hand everything so I don't know if this old horse can learn new tricks, but maybe....