Sharpening rc60 knife on a cheap combination stone.

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Oct 12, 2014
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I have a convex curved blade knife that I use for leather working, I only sharpen the first front part of the blade as the back part of the blade isn't used. The knife gets sharp enough that it can cut through paper (with a bit of drag and tears) but I feel that it still isn't as sharp as it can be with the cheap combination stone that I have (I think its 100 grit and 200 grit). Im not looking for the best stones but am looking for a all in one system or a combination water stone that can sharpen this hard of a knife. Would 200 grit and 400 grit get me to a sharp edge and most importantly keep it sharp for a long time or would I need to progress all the way to 1k grit.
 
What type of steel is it?

The hardness of the blade itself (60 RC) won't necessarily be an issue with most stones. If the steel is fairly high-alloy, with a large content of carbides (vanadium especially, but chromium carbides might also affect it), then the stone might have trouble with the carbides, which are at RC 70s-80s in hardness. Steels like S30V/90V/110V (heavy vanadium carbide content) and 440C, D2 or ZDP-189 (chromium carbides) would be examples of those.

Even 1095 at RC 60 will grind easily on most any stone, because it has no chromium-carbide or vanadium-carbide content.

A lot of 'cheap' combination stones will likely be aluminum oxide of an inferior quality (there are some very good AlOx stones however); the cheaper ones have been known to 'glaze' over with use, and they become ineffective. If so, lapping the stone to re-surface it might be needed. If it's a cheap stone, may not be worthwhile anyway. A good 'inexpensive' stone can be found in Norton's 'Economy' stone in silicon carbide; Home Depot carries that one, for about $7 or so. Ace Hardware carries an equivalent stone, also in silicon carbide; and I've recently seen what looks like an identical option at Sears as well. All these are so-called 'oil stones', but they work well with just water, or dry, or with dish soap & water, if that's what's preferred; the new ones come un-oiled.


David
 
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The website shows that the steel is CPM154CM. Im not too sure what that says about the knife.

Would a waterstone 4k/8k combination stone, 12k stone be a good idea along with a cheap stone to reshape the blade? The blade is really slim, around 1.5-2 cm in the middle coming to a point at the tip.

I want to just create the sharpest cutting edge for the longest time while not removing too much metal. I would think that 4k/8k combination waterstone ($50 shipped w/ flattening stone) already will give a good razor sharp edge, which is what I'm looking for or is this overkill?
 
The website shows that the steel is CPM154CM. Im not too sure what that says about the knife.

Would a waterstone 4k/8k combination stone, 12k stone be a good idea along with a cheap stone to reshape the blade? The blade is really slim, around 1.5-2 cm in the middle coming to a point at the tip.

I want to just create the sharpest cutting edge for the longest time while not removing too much metal. I would think that 4k/8k combination waterstone ($50 shipped w/ flattening stone) already will give a good razor sharp edge, which is what I'm looking for or is this overkill?
 
I have a knife of that steel and can easily sharpen it on a Norton fine India stone. It comes off very sharp, right off the stone. The blade off this stone cuts leather well. For some time. A coarse/ fine combination stone (Norton India) 2X6" will run 15$ and last several lifetimes. DM
 
Might hang around a bit, and wait for input from some of the waterstone experts here (maybe from 'Jason B'; he'd have very good advice). I haven't used waterstones, so I won't try to recommend which combination would be best for you. I'm certain quality waterstones would handle that steel, but there might be an ideal stone or two that one of the experts could recommend, IF you're sure that's what you want to use. With good waterstones, I'd think you shouldn't even need your cheap stone at all.


David (there seems to be a lot of us in here... :) )
 
Thanks for the help David and David :) There are a lot of David's in here.

The combination stone I have works well and by design the knife cuts extremely well because of the convex edge and thinness of the blade. I would like to get the blade so sharp that it cuts through the leather like its paper. So far its almost there with the combination stone, there is still something I feel missing to get it razor sharp.

I think a good sharpening with a high grit 1k/5k then 12k chinese water stone (apparently is worth way more than its sticker price - 20 dollars). If anyone one is familiar with high grit waterstones I could use some insight. I seen japanese kitchen knives sharpened on youtube with no micro bevel for 20 minutes on a 1k and 5k stone and would cut through vegetables with nearly any pressure. If I can translate that over to my convex knife I would be happy.
 
I use a green compound on a strop for a few strokes on each side. When I'm done with the combination stone similar to norton the edge is sharp and holds it edge for a short time, like 2 -3 minutes of cutting soft leather. The I go back on the stone and then strop.

It could be my technique or the compound itself, but I don't see any noticeable results after stropping. Im going to go with a 1k/5k waterstone and see how it goes.
 
Try more work on the stone you have with some back honing before going to the strop. Then stropping 60-100 passes on the green. Holding a good edge angle with medium light pressure. The green is not very aggressive. DM
 
I use a green compound on a strop for a few strokes on each side. When I'm done with the combination stone similar to norton the edge is sharp and holds it edge for a short time, like 2 -3 minutes of cutting soft leather. The I go back on the stone and then strop.

It could be my technique or the compound itself, but I don't see any noticeable results after stropping. Im going to go with a 1k/5k waterstone and see how it goes.


If it needs touching up that often, you might want to adopt a strategy closer to woodcarving. Keep a firm strop loaded with a somewhat more aggressive compound handy and strop more often. If the stone you're currently using is SiC, if used with oil you can reclaim some of the grit and apply it to a sheet of paper. Wrapped around the same stone it will serve as a very effective strop once the oil settles in and the grit can't slide around on the paper easily.


Flexcut Gold is another quality compound that can be applied to a leather strop or just rub some on a sheet of paper and wrap that around your stone. It has several grit sizes in it by design, so it can restore and refine an edge after some use instead of just refining a stone-sharp edge. Most makes of Black Emery compound are more aggressive as well and might work better than the green compound you're currently using. A hard backing will reduce any edge rounding from repeated stropping and allow the compound to work a little more effectively for constant maintenance.

Taking it to a higher polish initially should help with edge retention in this application as well, but for maintaining it daily, the waterstones might become a bit tedious.

The rig I sell through the link in my signature below is very effective at this sort of continual maintenance and is worth a look.
 
il take a look at flex cut, sounds promising.

In general sharpening by stone is the sharpest way and stropping overtime will eventually dull the blade and then it goes back on the stone and repeats the process?
 
il take a look at flex cut, sounds promising.

In general sharpening by stone is the sharpest way and stropping overtime will eventually dull the blade and then it goes back on the stone and repeats the process?


This is my take.


Sharpening by stone makes the flatest possible cutting plane. When you strop on a surface with give, the edge is going to take on the shape of the arc defined by the amount of give (how soft the strop surface is and how much force is being applied).

The strop surface is somewhat conformable and it wants to spring back to its original volume as the edge passes over. So in addition to any overall convexity, you can have even greater rounding right at the cutting edge until the shape of the edge comes into equilibrium with the arc defined by the strop surface.

If you're only giving it a few light passes off the stone this isn't really an issue, if you're doing it constantly, over time it can make your edge way more broad than is good for effective cutting. Using a harder backing can help this out considerably. Since it won't deflect as much, one can apply a modest amount of additional force, and/or it will be more tolerant of variations in applied force from repetitive use - it will come into equilibrium with a much more shallow arc.

This also allows the compound to do more restorative work. Very handy, as stropping generally doesn't cause anywhere near the level of burring a hard stone will, so less time spent on QC and less need for fine angle control as the slight bit of deflection (hopefully no more than a degree or so) increases the margin of error you need to hold the edge at and still have the compound working effectively at the apex.

Also, most stropping tends to reduce all the fine irregularities along the cutting edge left over from the stone work - not necessarily a benefit for EDU, but for slicing leather you're probably better off with a thin ground edge that is more refined/uniform anyway.

Flexcut, being formulated for wood carvers, does a good job in terms of prolonged maintenance as it has a small percentage of larger grit for "grinding" a fresh cutting edge, and a large percentage of finer grit for refining it - all in one step. This is the same strategy I use in my custom honing compound included with the kit I make. Did a lot of trials and for general maintenance use, the multi grit formulations outperformed the single grit ones every time.

If you do simply apply the compound to a sheet of paper and wrap around the stone, I highly recommend using the coarse side. It allows the paper to deflect into the low spots on the stone and it won't push back up so hard as the edge passes over. The spots that do ride on the high points in the stone will permanently compress the paper a bit more than they would over a flat surface, and this action reduces the tendency to expand back up at the contact points as the edge passes over (another trait I adopted when making my Washboard). Just brush off the stone - a few swipes with your hand will do - before using, as any loose grit trapped under the paper can deform the cutting edge with surprisingly little appled force.

I prefer to use paper over a stone or one of my Washboards, because once you start to do more stock removal with a compound, it will load up much more rapidly than it will when used for a light final polish. Instead of having to clean it off all the time, just toss the paper and start fresh with a new sheet. If you opt for a leather strop make sure it is well cased and very hard. Balsa is another common choice.
 
Martin,

Your explanation on compression & deflecting above is much better than any I've read before and suddenly lighted up a bubble in my mind. I know you have said it in the past, but somehow I didn't really got it until now. :o

Thanks!
 
Chris "Anagarika";14060916 said:
Martin,

Your explanation on compression & deflecting above is much better than any I've read before and suddenly lighted up a bubble in my mind. I know you have said it in the past, but somehow I didn't really got it until now. :o

Thanks!

Chris, I think most people after a bit of trial and error develop an instinctive feel for it. I've had to spend a little more time on this as its an important part of how the Washboard works, and an important factor in how I go about most of my sharpening and maintaining even without a Washboard. Don't want to hijack the thread, but I could go on about this for a few, including a handful of micrographs that illustrate some of the principles.
 
I would be interested in a tutorial post from dull to razor sharp using your washboard sharpening system.
 
David, if you want to go the water stone route, the is a king combo stone that I use that works very well. I believe it's 250 grit on one side and 1000 on the other. I also go to the king 6000 and if I'm feeling froggy the Chinese 12000 that you were talking about. That will give you a great polished edge that sails through leather. A little bit of stropping should maintain that edge for a little while. That's the set up I use on my little carving/leather cutting knife
 
I would be interested in a tutorial post from dull to razor sharp using your washboard sharpening system.

I can make up one with a still photo presentation if you'd like, the website (http://www.washboardsharpening.com/) has a write-up, micrographs, electronic copy of the user's manual, a bunch of video tutorials, and there are a handful more under my youtube name 'Neuman2010', as well as some other sharpening videos showing other media. I haven't been pushing it very hard on the forum since I started up the website.

This is one showing a leisurely progression on a convex Bark River, Sandvik stainless using sandpaper and honing compound:
https://www.youtube.com/watch?v=SalomUAvMHI

and a more recent one - the newer blocks are black, not clear, come 2"x8"x1" and have their own bases that double as a mounting system for the sandpaper or lapping film. Sandpaper can usually just be folded tight around the block, but lapping films, esp used with mineral oil, really need to be held tight. The bases make it work a bit better as a stand-alone and can pin down lapping films to 6" (big price break between 6" diamond films and the larger sizes).

Anyway, this one is showing the Norton econo stone, and a Washboard that has been cut down to size in conjunction with the reclaimed grit from the Econo stone:
https://www.youtube.com/watch?v=DF2Y7Hha0MQ

It does a very good job with sandpaper and lapping film in addition to being a potent stropping base - allows less deflection of the paper or film - hardens it up some, so makes for a more crisp V bevel than is generally common with those media. For a maintenance strop used with paper, I do not believe it has an equal - all depends on one's maintenance strategy and needs.

Martin
 
This is my take.


Sharpening by stone makes the flatest possible cutting plane. When you strop on a surface with give, the edge is going to take on the shape of the arc defined by the amount of give (how soft the strop surface is and how much force is being applied).

The strop surface is somewhat conformable and it wants to spring back to its original volume as the edge passes over. So in addition to any overall convexity, you can have even greater rounding right at the cutting edge until the shape of the edge comes into equilibrium with the arc defined by the strop surface.

If you're only giving it a few light passes off the stone this isn't really an issue, if you're doing it constantly, over time it can make your edge way more broad than is good for effective cutting. Using a harder backing can help this out considerably. Since it won't deflect as much, one can apply a modest amount of additional force, and/or it will be more tolerant of variations in applied force from repetitive use - it will come into equilibrium with a much more shallow arc.

This also allows the compound to do more restorative work. Very handy, as stropping generally doesn't cause anywhere near the level of burring a hard stone will, so less time spent on QC and less need for fine angle control as the slight bit of deflection (hopefully no more than a degree or so) increases the margin of error you need to hold the edge at and still have the compound working effectively at the apex.

Also, most stropping tends to reduce all the fine irregularities along the cutting edge left over from the stone work - not necessarily a benefit for EDU, but for slicing leather you're probably better off with a thin ground edge that is more refined/uniform anyway.

Flexcut, being formulated for wood carvers, does a good job in terms of prolonged maintenance as it has a small percentage of larger grit for "grinding" a fresh cutting edge, and a large percentage of finer grit for refining it - all in one step. This is the same strategy I use in my custom honing compound included with the kit I make. Did a lot of trials and for general maintenance use, the multi grit formulations outperformed the single grit ones every time.

If you do simply apply the compound to a sheet of paper and wrap around the stone, I highly recommend using the coarse side. It allows the paper to deflect into the low spots on the stone and it won't push back up so hard as the edge passes over. The spots that do ride on the high points in the stone will permanently compress the paper a bit more than they would over a flat surface, and this action reduces the tendency to expand back up at the contact points as the edge passes over (another trait I adopted when making my Washboard). Just brush off the stone - a few swipes with your hand will do - before using, as any loose grit trapped under the paper can deform the cutting edge with surprisingly little appled force.

I prefer to use paper over a stone or one of my Washboards, because once you start to do more stock removal with a compound, it will load up much more rapidly than it will when used for a light final polish. Instead of having to clean it off all the time, just toss the paper and start fresh with a new sheet. If you opt for a leather strop make sure it is well cased and very hard. Balsa is another common choice.

Denim wrapped around a stone solved the issue for me.

That said, I can easily maintain my edges using nothing more then an 8k waterstone and a strop. Once it becomes too dull to easily cut paper I just strop it, if that doesn't fully restore it I hit the 8k. The only time I go down to fully restore a bevel is if a damage the edge or its a knife that's entirely dull, I often don't bother sharpening kitchen knives until they reach that point because their thin edge geometry will cut easily up to the point.
 
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