Sharpening time for different steel hardness

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Wil lRogers

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Oct 29, 2013
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How much longer does it take to sharpen a knife based on its steel hardness? To be more specific, given three knives made of VG-10, CPM S30V, and CPM20CV (a random sample of steels from softer to harder), how much longer (roughly) would you would you expect it to take to sharpen the latter two compared to the VG-10 blade? E.g. "twice as long for CPM S30V compared to VG-10"?

The Spyderco Sharpmaker instructions recommend 20 strokes per side with each of the four stone settings (brown corner and face, white corner and face), but that must vary by steel hardness. But vary by how much?
 
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A lot of the time required to sharpen depends on how dull the knife is to begin with, as well as how wear resistant the steel is plays a factor in sharpening time. I’ve found that with wet/dry sandpaper (my preferred sharpening media) that a slightly dull VG-10 and S30V don’t take too long to sharpen where as CTS204-P might take 50% longer. Although I can’t say whether they were r all the same level of dullness to begin with so it isn’t a hard scientific number
 
As long as it takes.
Sharpening skills, equipment and method will produce different results on the same steel. So, the replies are going to be all over the place.
For me, it's not so much the steel as it is the consistency with each individual knife. I've just started logging angle, clamp placement and depth in the clamp on the knives I own to make the sharpening process more efficient. Reading the Maintenance sub forum has helped me in my skills to be a better sharpener. I read the threads on a regular basis.
 
Well, I meant if the three knives were equally dull. Saying that CTS204-P (which I gather is very similar to CPM20cv) "might take 50% longer" is the kind of answer I was looking for. I was wondering if someone would say "CPM20cv takes ten times as long to sharpen as VG10."

I wasn't asking for a scientific study, although I'll bet there are members of BladeForums who have done semi-scientific studies of sharpening time for different steels.

Silvanus said:
A lot of the time required to sharpen depends on how dull the knife is to begin with, as well as how wear resistant the steel is plays a factor in sharpening time. I’ve found that with wet/dry sandpaper (my preferred sharpening media) that a slightly dull VG-10 and S30V don’t take too long to sharpen where as CTS204-P might take 50% longer. Although I can’t say whether they were r all the same level of dullness to begin with so it isn’t a hard scientific number
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Most of my sharpening time is spent reprofiling factory edge bevels. I like edges to be around 20 dpi, most aren't, and a lot of times one side is a little different than the other. The initial reprofiling can take a crazy amount of time, I use a diamond on super steels to set the bevel then switch to stones to refine and polish it.

Steels like M390, 204p, cpm20cv etc. can take a couple hours to reprofile for me. S35vn is on the edge, don't really need a diamond but it makes short work of reprofiling and takes about 1/2 the time as the other steels mentioned.

To touch up an already reprofiled edge takes hardly anytime, straightening and refining the current bevel can be done pretty quickly, mostly I just use a strop until the edge shows signs of micro damage or worse then I'll get out the stones. I only use diamonds for removing a lot of metal or fixing a damaged edge (chips, dents, hard rolls, etc).

Sharpening for me is a bit cathartic, I enjoy it and spend a lot of time ensuring my edges are even and slicey.

I'm not sure how to quantify the time differences but I would say between a carbon steel and a hard powdered steel it's probably greater than 50% more time w/super steels, maybe more. That's reprofiling, seems once a good edge is developed maintaining it is roughly the same between the 2 but you will do it more often w/carbon steel and probably use different stones.

I don't really have many softer steels that I use and have spent more time w/the higher end steels. I've spent 4 hours reprofiling an M390 edge and taking it to a mirror. A Buck I can do the whole process in under an hour.

I've never been a stroke counter, more about time per side and using good lighting to see the edge come together. A sharpie and good light are essential for me, good light being the most important as you can watch the edge develop and see the areas that need more attention. Most times the grind near the tip and the choil take the longest time to come together so more time is spent there than along the main edge bevel. If you're not getting a uniform, full length burr your not going to get a sharp knife.
 
It really depends on what exactly the sharpening entails for the specific blade.

If I have a Maxamet blade brand new and want to just sharpen to existing factory angle and take off factory grind I can do 220-320 grit plate and have it done in 10 minutes, maybe less.

Now if I gotta reprofile to lower angle then refine to higher grits then we get into substantially more time.

Evaluating what needs to be done to the edge and how exactly to do it can be a difficult task, especially for beginners.

Also you do not want to attempt to take off a lot of steel with Sharpmaker ceramics unless you have lots of time, Barkeepers Friend, and patience.
 
With 1x6 diamond stones I find there is virtually no difference, maybe 20% between a good stainless and Maxamet. In a way the harder the better as it makes it easier to polish. There might be a little more difference if reprofiling depending on the bevel width.
 
Most of it depends on how much steel has to be removed, AND if the work is being done with stones appropriately matched to the steel and the job. That means working high-carbide steels with abrasives that are able to handle those carbides easily. Some of the easiest sharpening jobs I've experienced involved wear-resistant steels like S30V, S90V, or D2. But the key was, I used abrasive types appropriate to the steels (diamond for S30V/90V, and silicon carbide for D2). If I'd tried simple Arkansas stones, or even a typical oil stone in aluminum oxide, those same jobs with the same steels would've taken much, much longer, if they ever really got done at all.

The simple size of the stones makes a big difference also - larger stones enable longer sharpening passes and a more aggressive technique (heavier pressure, faster and more fluid tempo), which greatly speeds up the work. A typical guided system with small stones, even if they're of the appropriate abrasive type and grit size for the job, could take up to 4X-6X as long to finish a big grinding job as it would take using a stone of the same abrasive type and grit rating, but in a benchstone-sized format.
 
Wil lRogers, this ^. If it takes me more than 20 mins. to get a sharp working edge on a knife using stones. Then somethings wrong with my technique or I'm not using the right stone. Many times I'll switch to a coarser stone. DM
 
May I assume that if other things are equal and I need to sharpen and not to re-profile, and using diamond stone it will take about the same time (may be 20% difference) to sharpen soft steel like VG10 to hard powder metallurgy steels?
 
Barmaley said:
May I assume that if other things are equal and I need to sharpen and not to re-profile, and using diamond stone it will take about the same time (may be 20% difference) to sharpen soft steel like VG10 to hard powder metallurgy steels?
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In my experience, yes. Diamonds make all the difference.
 
Barmaley said:
May I assume that if other things are equal and I need to sharpen and not to re-profile, and using diamond stone it will take about the same time (may be 20% difference) to sharpen soft steel like VG10 to hard powder metallurgy steels?
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With diamond, cutting speed shouldn't matter much either way, as far as the actual hardness of the steel is concerned.

Some ductile stainless steels at medium hardness, like VG-10 at mid/high 50s HRC, can actually create more issues with clogging on a diamond hone or other stones, if some means of lubrication isn't used (like water, oil). These stainless steels tend to leave more ribbon-like shavings of steel on the hone, rather than 'chips' left by harder steels. The shavings can cling tenaciously to the surface of the grit, unless some lubrication is used to prevent that. That can slow things down, if the hone isn't kept lubricated, clean & unclogged. High-alloy, high-carbide PM steels don't usually exhibit the same clogging behavior though, and can sometimes be easier to sharpen on diamond than many simpler steels might be, assuming other factors like geometry and amount of metal to be removed are the same.
 
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David Martin said:
What slows grinding down with the use of diamond is using light pressure. So, you won't sheer the diamonds off the plate. DM
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Agreed, but depending on how the stone is made, it may be more of how deeply it cuts or how deep the grooves in the steel will be. A resin bonded stone wont tear up like a diamond bonded on steel plate will.
 
Barmaley said:
May I assume that if other things are equal and I need to sharpen and not to re-profile, and using diamond stone it will take about the same time (may be 20% difference) to sharpen soft steel like VG10 to hard powder metallurgy steels?
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Addressing this point specifically, re: just sharpening vs. reprofiling...

The point raised about light pressure slowing things down is entirely moot, in simple resharpening of an edge already set to good geometry. In fact, when doing simple resharpening on diamond, light pressure is all that's needed and it'll do the work very quickly, often in just a handful of passes at a very, very light touch. In my uses, once I've set an edge to the geometry I want, it generally doesn't take more than maybe 3-5 minutes at most, to tune up an edge with a very light touch.

To speed up things when I'm doing heavier grinding on a diamond hone, it helps a lot to keep a film of lubrication on the hone, to keep swarf from clinging. I like mineral oil for this, especially. And I do believe the oil will help protect the hone from the excessive friction generated by dry honing, and therefore reduces the wear on the hone itself. Pressure just needs to be moderated to medium/firm - it's not like the diamonds will be ripped out if anything more than a featherlight touch is used, of which that assumption is often vastly overexaggerated. Good quality hones like DMT will last a long time, used with a medium-to-light touch, as determined by the needs of the task itself.
 
David, there are more than just me that say diamonds fracture / shear off during use. I'll admit I was reprofiling a 440c, 9" blade. When mine showed it, the x coarse stone was new. It was way broke in when I finished. Now I don't use it much. I'll grant you have a point about light touch, After the bevel is set. But it took me some time to get to the setting part. And I was not using as much pressure on that plate as I do on my SiC coarse stone during reprofiling. Which is part of why it took longer & I was using water. DM
 
Why don't use diamond stone for all applications? (this is what I am currently use). Is there any limitation or disadvantage of it?
 
Diamonds are more aggressive by nature, so they may remove more then needed or get clogged with steel. I then use sic stones
 
sickpuppy1 said:
Diamonds are more aggressive by nature, so they may remove more then needed or get clogged with steel. I then use sic stones
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I'm not sure he should be taking advice from a sick puppy, but I'm not sure what it says about me if I agree...
 
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