An edge that lasts

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robinbj

Joined
Jul 29, 2015
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I've been sharpening knives for years, my own for a long time.

When I started, I used wet stones, and a few mechanical "pull through" rippers. Lately, the knives I've sharpened over the past 2 or 3 months have been coming back dull, unable to cut effectively and not holding an edge. I work primarily with wet stones, and my edges would stay sharp for months. Guys that use their knives for just about everything raved at my work. Now it's gone to crap.

Here's what I know so far
1 the edge rolls overs
2 stones are flat, unhollowed, and in good condition

Anybody have any suggestions on how I can improve my end result? I'm not sure where to go, I'm a bit baffled.
 
I usually run a 18-24deg primary edge up to 30 depending on the steel/use ect. Might I be rounding the edges too much? Not flat enough of a grind?
 
My thoughts are that either your angles are becoming inconsistent when sharpening, you are not adequately removing the burr, or could it be the steel itself? Are the knives made of softer steel that isn't staying sharp or could it be that you are sharpening harder steels and your stones are not abrasive enough? I think we need a little more information. I am not an expert by any means though. I guess my first question is are you hitting the apex when sharpening? I would suggest using a sharpie to mark the edge to test this.
 
robinbj said:
I've been sharpening knives for years, my own for a long time.

When I started, I used wet stones, and a few mechanical "pull through" rippers. Lately, the knives I've sharpened over the past 2 or 3 months have been coming back dull, unable to cut effectively and not holding an edge. I work primarily with wet stones, and my edges would stay sharp for months. Guys that use their knives for just about everything raved at my work. Now it's gone to crap.

Here's what I know so far
1 the edge rolls overs
2 stones are flat, unhollowed, and in good condition

Anybody have any suggestions on how I can improve my end result? I'm not sure where to go, I'm a bit baffled.
Click to expand...

Where are the knives coming back from? And if those knives were 'used for just about everything', what specific uses would that be? If this change in edge-holding character is something relatively recent and occurring on knives you've previously sharpened successfully for somebody else, I'd start wondering if those knives have been abused enough to damage the heat treat in them. Lots of other questions too, including what steel types are they? And have any of the knives been sharpened/ground on powered tools, aside from the wet stones you've used?

Assuming there's no damage to heat treat, edges that roll over quickly are often an indicator of inadequate burr-removal, assuming the steel quality is decent for the way it's being used. Might also indicate the edges are ground too thin to hold up to the tasks they're being used for. Right now, I think it's important to know how those blades are being used (or abused??).


David
 
Obsessed with Edges said:
Where are the knives coming back from? And if those knives were 'used for just about everything', what specific uses would that be? If this change in edge-holding character is something relatively recent and occurring on knives you've previously sharpened successfully for somebody else, I'd start wondering if those knives have been abused enough to damage the heat treat in them. Lots of other questions too, including what steel types are they? And have any of the knives been sharpened/ground on powered tools, aside from the wet stones you've used?

Assuming there's no damage to heat treat, edges that roll over quickly are often an indicator of inadequate burr-removal, assuming the steel quality is decent for the way it's being used. Might also indicate the edges are ground too thin to hold up to the tasks they're being used for. Right now, I think it's important to know how those blades are being used (or abused??).


David
Click to expand...
Most of these knives have not been touched by any power equipment. I re establish the primary edge with a 1k grit stone and strop polish on the 6k grit. Most of these knives are 8cr13mov, vg10, 530, 440c, ect. A few d2 that use ceramic on.

My finishing on each stone is a stropping motion trailing the blade on both the 1 and 6k stone, and a light drag through soft wood to finish burr removal. It's what I was taught by others who have been at it much longer than I
 
Just two stones will not fulfill all the needs of a professional.

6k is also far too high of a polish for most anything that gets used hard. It's especially bad on softer steels because they will probably take the sharpest edge with your method but they just won't hold it in use. You would probably be better off just using the 1k followed by some light stropping.

With waterstones, I prefer the 2k grit as a finishing point for many of the reasons you listed. For me it's a good balance of toothy and polished that provides controlled cutting, long edge retention, and Just enough polish to please the customer.

I would recommend possibly changing up your stone line-up to better suite your customers. A good 400-500 grit stone followed by a 2000 grit stone would give you much more flexibility and better edges for your customers.
 
If Op prefers King for common steels, the 1200 is probably my favorite of the entire King lineup. Sort of a bridge between grinding and polishing and makes a great utility edge.
 
I've worked with king stones, they wear away a bit fast for me. I might try only finishing with the 1k, saving the 6 for the more necessary tools such as kitchen cutlery ect.
 
I've found that my 1k and 6k do a majority of my work, my 400 and 600 are really for heavy reshaping, and that's been my process all along. Only recently have my work shifted to pocket knives and they aren't holding nearly as well with that system. So I think I'll try keeping the edges at a lower grit, more toothy and slightly less refined.
 
Coming off the 1k, if you get it clean with no burr, you can limit the number of backhone passes on the 6k to keep it more toothy.

I also have reclaimed some of the grit from the 1k stone work, wiped it up on a sheet of paper and let dry - wrap around a dry stone - a coarse one works best, and use that for a strop off the 1k. Cleans up the edge, refines it just a bit more into that 2k range for utility.

https://www.youtube.com/watch?v=RXr-FPME-jc
 
I just encountered something that I've not really encountered before, the persistent burr. The knife doing it is a low alloy high carbon steel at approximately 61 RC. I've sharpened it probably 5 times, each time I sharpen it it seems to be getting harder to cut the burr off before I go to strop. Now it seems like when I flip the knife over for the last light edge leading stroke it'll just flip the burr to the other side no matter how lightly I swipe the blade. I don't normally form a heavy burr at low grits, I go until I feel the slightest catch and then flip and repeat up through my stone selection. I don't seem to have any of these issues with any other steels I've sharpened ranging from cheap stuff through more expensive steels, from low alloy up through high alloy steels. It's just this one. I've also noticed the edge retention going down and I'm sure it has to do with me flipping the burr back and forth which is weakening the apex.


Any words of advice?
 
bodog said:
I just encountered something that I've not really encountered before, the persistent burr. The knife doing it is a low alloy high carbon steel at approximately 61 RC. I've sharpened it probably 5 times, each time I sharpen it it seems to be getting harder to cut the burr off before I go to strop. Now it seems like when I flip the knife over for the last light edge leading stroke it'll just flip the burr to the other side no matter how lightly I swipe the blade. I don't normally form a heavy burr at low grits, I go until I feel the slightest catch and then flip and repeat up through my stone selection. I don't seem to have any of these issues with any other steels I've sharpened ranging from cheap stuff through more expensive steels, from low alloy up through high alloy steels. It's just this one. I've also noticed the edge retention going down and I'm sure it has to do with me flipping the burr back and forth which is weakening the apex.


Any words of advice?
Click to expand...

Best advice I can think of is to remove the burr when it first forms. Once it starts to flip, as you've found, it will flip with increasing ease until the amount of force needed to generate some abrasion to remove it is greater than what it takes to flip. At that point you might as well cut it off by running lightly across the stone at 90° and removing the drawn out steel - start over.

Here's some general tips. For the first one, if using a hard stone, alternate with leading passes on the stone instead of trailing passes on the wet/dry.
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bodog said:
I just encountered something that I've not really encountered before, the persistent burr. The knife doing it is a low alloy high carbon steel at approximately 61 RC. I've sharpened it probably 5 times, each time I sharpen it it seems to be getting harder to cut the burr off before I go to strop. Now it seems like when I flip the knife over for the last light edge leading stroke it'll just flip the burr to the other side no matter how lightly I swipe the blade. I don't normally form a heavy burr at low grits, I go until I feel the slightest catch and then flip and repeat up through my stone selection. I don't seem to have any of these issues with any other steels I've sharpened ranging from cheap stuff through more expensive steels, from low alloy up through high alloy steels. It's just this one. I've also noticed the edge retention going down and I'm sure it has to do with me flipping the burr back and forth which is weakening the apex.


Any words of advice?
Click to expand...

Don't try to 'flip' the burr on edges like these, except for the first 'flip' that happens when you verify the edge is fully apexed from both sides. I have a few knives at fairly high hardness like this (60+ RC blades in ATS-34, for example, have amazingly tenacious, hard & tough burrs); the only effective way to get rid of the tenacious burrs on them is to very gently & gradually abrade them off. Dragging the edge through wood seldom, if ever, removes them either; they don't budge. I've always worked at very, very lightly abrading them off, by slightly raising the angle a bit and using extremely light edge-leading passes on the stone to basically file the burr away. Light touch is EVERYTHING when doing this, as a heavier stroke will just make more/bigger burrs.

A very clean-cutting hone, like diamond or SiC, is usually more effective at removing them with a very light touch. Hones that don't cut quite as cleanly (lower quality AlOx or natural stones) will tend to force use of heavier pressure to abrade very hard steels, which is counterproductive.


David
 
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