I've been learning about and sharpening knives the past few months, and I have quite a few questions

Kitchen Knife Forums

Help Support Kitchen Knife Forums:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Flyingpigg

Well-Known Member
Joined
Jul 21, 2013
Messages
66
Reaction score
0
I consider myself a journeyman on knives and knife sharpening (I know more than people who don't care much for knives, but I don't consider myself an expert), and I'd really like to take my knife sharpening skills and knife knowledge up to the next level so I have a multitude of questions I'd like to get answers to. I've watched Jon and Carter's videos on YouTube, and I've been reading this forum along with zknives for awhile. I'm a really picky person though, and there are just a lot of things that I'm still curious about that I'd like to get more information on.

Anyways, here goes:

1. What about diamond stones? I currently use water stones with a diamond plate for flattening, but it seems like diamond stones come in pretty fine grit now too. Why does everyone advocate the use of water stones over diamond? The only disadvantage I can see would be that the diamonds would cut much more aggressively with leaves less room for error, although this maybe an advantage for some because it'd cut quicker. It seems like the feedback on diamond stones would not be as nice as water stones either, but I think this is a personal preference matter.

2. What am I suppose to be looking for when using a loupe? I bought a loupe because they're cheap, and I kept seeing people say to check your edge with a loupe. I'm seeing things with it, but I'm not exactly sure what these things mean. Any nicks and chips, I can usually spot with my naked eye if I try hard enough, although the loupe does it make easier to spot. I noticed different colors (or difference degrees of shine) on my edge bevel when I first started sharpening, and I felt that this meant I was not holding my hand steady enough thus changing angles while sharpening (thankfully, I'm better at it now). Is my assumption true, and what else can I use loupes for when it comes to knives?

3. How do I deburr on cork and soft wood? I've tried doing this a few times where I deburr by lightly cutting a knife into a wine cork (does it matter if the cork is synthetic or natural?), but I've always felt a burr on the knife after cutting through cork. I've been practicing with my coworker's German knives, and I've read that the softness of the steel makes the burrs more difficult to remove. Could this be part of the reason as to why this deburring technique doesn't work for me? I usually just end up using a fine ceramic rod or stropping lightly on my Suehiro Rika 5k to remove the burrs. I did just get a balsa strop which I loaded with chromium oxide paste and a leather strop (natural cured, cowhide), but I haven't really used it much yet.

4. Should I be worried about swarf contamination in my stone soaking water? My current stone set up is a King 1k, Bester 2k, and Suehiro Rika 5k, and I usually soak all three stones in the same container or sink. As I sharpen my knife, I'll splash water onto the stone using the water from this container, and I'll periodically wash my blade off which causes the swarf to contaminate the water. When I switch to a finer stone, I'll rinse the stone off real quickly, but should I be changing the water too so the coarser grit stone material doesn't affect the performance of the finer stone? For now, I change the water just to be safe, but I believe that clean water is very precious (I studied crop science in college, and our water supply is my biggest concern over other stuff like fertilizer and pesticide use) so I try to not to waste any if I can. Also, should I be washing the swarf off periodically? I've read that the swarf actually does a lot of the sharpening, so I try to keep it on, but is there a point where I'm leaving too much on?

5. How big of a concern is stone clogging with water stones? I'm noticing grey streaks in my stones as I sharpen, but due to this series of comment on Reddit, I believe that stone clogging is more of a concern with oil stones than water stones. I feel like water stones are usually soft enough that the sharpening motion will simply knock out metal and stone particles, and as a result, I shouldn't have to worry about clogging. I also haven't noticed much sharpening issues with these streaks in my stones, but like I said, I'm still learning about knives so I might just not be experienced enough. I'm assuming I can just use the little stone cleaners or lightly lap my stones with a diamond plate to unclog if clogging is an issue.

6. How flat does my stone have to be, and how can I tell if my stone is slightly dished? I also feel like the flatness of the stone matters more depending on the type of knife I'm sharpening, like a single bevel knife or very flexible/whippy knife, but can anyone confirm this for me? I try to use Carter's suggestion with spotting high spots on the stone and sharpen more in this area. I tend to notice high spots on the corners of my stones, and I rotate my stone when I'm sharpening so I wear it out more evenly. I also try to do most of my tip sharpening in these high spots. However, how flat does the stone have to be? I usually use a flat surface, and I just lay the stone against the flat surface to see if I have any indents, although I feel like this means the stone has to be pretty dished for me to see it. Should I be using another method, perhaps a level?

7. Should I be flipping the knife periodically as I sharpen? I've read some suggestions that I should just be sharpening one side until I feel a burr, then repeat the same number of strokes on the other side. However, I feel like this will cause uneven grinds, and I try to flip the knife every so often. I feel like I'm not being consistent enough with it, and it seems like one side of my knife is getting ground more than the other side. My beliefs are a result of observing the choil, and it just seems like a certain side is more slanted than the other when I don't flip the knife regularly during sharpening.

8. How can I tell if I have an overgrind and possible ruining of heat treatment? I've been thinning my knife because it's pretty thick behind the edge (it's a Richmond Artifex, I'm using it as my beater/learning knife), and I noticed a low spot on my edge (I'm calling it a low spot because I'm holding the edge upwards, although if the edge was down on the board, it's be a high spot). At first, I thought I just screwed up when sharpening/thinning it as I don't have a smooth motion down yet (I sharpen in sections and try to keep count of strokes, slowly progressing to less counts), but after reading the thread about Moritaka's overgrind, I'm beginning to suspect that it's an overgrind. The reason I suspect this is because I'm starting to see discoloration (like purplish-blue tint that's slightly reflective, almost like soap streaks on a water surface) on the surface of the blade behind where this spot, and it's only starting to show up as I've thinned and expose the inner metal. Is this discoloration of any concern? I'll try to get a picture of it, but I feel like it's going to be difficult to get the right light and angle for it to show up on a picture. I wish I had known more about overgrinds when I first got the knife, but I didn't really know how to spot them when I first got it a few months back so I don't know if this was an issue from the beginning.

9. How do I sharpen the flexible German boning knives (or any flexible knives in general; I've yet to had the pleasure to use a laser), especially around the heel where there's that curve. Perhaps I should just not care about sharpening this curve though as it doesn't really get much use anyways.

10. How does knife geometry affect food release? I've been watching all the videos on food release in the media center section of the forum, and I'm just confused as to why the Gesshin Heiji seems to perform so well in this category. I've read that the Gesshin Heiji's grind is a little bit concave, and this improves food release. However, I read on zknives that hollow grind increases drag, but maybe drag doesn't have the effect that I think it does.



Hopefully, these aren't too many questions. I don't like to say thanks before someone does something because it seems presumptuous to me, but any answers provided will be greatly appreciated.
 
1. What about diamond stones?

I've used them, and they work quite well, but as you note, there is little or no feedback, so they are not my favorite for general sharpening, but they are great for thinning, because they don't dish, ever.

2. What am I suppose to be looking for when using a loupe?

All a loupe does is make it easier to see things like faceted bevels instead of clean, flat bevels, and if you are hitting the edge when using the "marker trick". No magic here, just an aid to those of us with older eyes.

3. How do I deburr on cork and soft wood?

You make a shallow cut into the cork, felt block or soft wood and the slicing action should tear the burr off the edge. If you are having troubles, it may be because the connection of the burr to the edge has not been sufficiently weakened by working both edges alternately. Try trailing edge stropping to help weaken the burr.

4. Should I be worried about swarf contamination in my stone soaking water? Also, should I be washing the swarf off periodically? I've read that the swarf actually does a lot of the sharpening, so I try to keep it on, but is there a point where I'm leaving too much on?

You should be rinsing off your stones as you remove them from your soaking water, and it's not a bad practice to rinse them before replacing them. It doesn't require a lot of water - a quarter cup should be sufficient.

5. How big of a concern is stone clogging with water stones?

The thing about waterstones that makes them different from oil stones is that the surface of the waterstone is constantly abraded to reveal fresh sharpening material. It's really hard to clog one, but if it happens, it's usually because your not using enough water during sharpening.

6. How flat does my stone have to be, and how can I tell if my stone is slightly dished?

Use a straight edge to judge how dished your stone is, as Jon Broida illustrates in this post:
http://www.kitchenknifeforums.com/s...re-be-interest?p=238350&viewfull=1#post238350

For me, less than 1 mm of "dish" is acceptable, but YMMV.

7. Should I be flipping the knife periodically as I sharpen?

Yes, but here's where that loupe can help you, if you use the marker trick to tell you when you hit the edge rather than trying to detect a burr.

8. How can I tell if I have an overgrind and possible ruining of heat treatment?

Overgrinds generally do not affect the heat treatment. There is a whole tread about overgrinds, and how to determine if you have a real problem. Again, Jon Broida summed it up well in this post from the thread:
http://www.kitchenknifeforums.com/s...itaka-how-long?p=235100&viewfull=1#post235100


9. How do I sharpen the flexible German boning knives (or any flexible knives in general?

Very light pressure is the key to sharpening a flexible knife. It's tricky. The recurve area can be sharpened with a curved hone, or with a dowel wrapped in wet/dry of the appropriate grit.

10. How does knife geometry affect food release?

Generally speaking, the more convex the grind, the greater the tendency for what is cut to be pushed away from the side of the blade as the cut progresses. There are more factors at work here than just geometry - the characteristics of the product that is cut, for example. A soft cheese will stick to most every knife, while a hard, fibrous sweet potato won't. A mirror polish on a knife with minimal convexing is probably the worst offender, at least in my experience. Keep in mind that there is a trade-off here, in that knives with really convex grinds usually don't "fall through food" well.
 
This is useful information! Thanks.
 
I have read that diamond plates are too hard to use for sharpening Japanese knives as they will cause micro-fissures/chips. I haven't tested this theory out for myself but it sounds good enough for me.
 
I have read that diamond plates are too hard to use for sharpening Japanese knives as they will cause micro-fissures/chips. I haven't tested this theory out for myself but it sounds good enough for me.

Seb, I think that meme is right up there with the "VG10 is chippy" one.

Rick
 
When the diamonds are electrically plated to the surface, they can have a lot more surface area exposed, and this can sometimes cause what's seb is talking about... Especially when coarser grits are involved. It's because they will cut deeper in this particular kind of scenario.

But if you spend enough time going through your progression, all of the problems caused by this coarse grit diamond will be gone.
 
When the diamonds are electrically plated to the surface, they can have a lot more surface area exposed, and this can sometimes cause what's seb is talking about... Especially when coarser grits are involved.

I'm curious about this myself. I only use DMT plates...all the others I've tried are horrible...the diamonds roll out and seriously scar up the work. Not to mention they just plain aren't flat.

I also noticed that the difference between extra coarse, and extra-extra coarse...is like a million miles. Extra-extra is like 27 seriously large diamonds bonded to an 8x3 plate, lol. Extra was actually relatively smooth once broken in. I love the way it cuts. I'm not using those grits for sharpening though...so I'm sure that makes a difference.
 
I'm curious about this myself. I only use DMT plates...all the others I've tried are horrible...the diamonds roll out and seriously scar up the work. Not to mention they just plain aren't flat.

I also noticed that the difference between extra coarse, and extra-extra coarse...is like a million miles. Extra-extra is like 27 seriously large diamonds bonded to an 8x3 plate, lol. Extra was actually relatively smooth once broken in. I love the way it cuts. I'm not using those grits for sharpening though...so I'm sure that makes a difference.

I don't use XXC on knives, only for flattening stones. XC is pretty nice once broken in, for thinning.
 
I don't use XXC on knives, only for flattening stones. XC is pretty nice once broken in, for thinning.

Yes, what I'm doing with the extra coarse would compare with thinning. It leaves a really nice finish once you wear the new off of it. For sharpening I use extra fine and extra-extra fine, then go to diamond loaded felt strops. It seems to work wonderfully for me...leaving a nicely polished but 'sticky' edge.

Again though, as a disclaimer, I've only used even these on AISI W1 and W2 (not white 1 and 2) tool steel hardened and tempered to around 62+ Rockwell. That's one reason I was curious about the chipping thing Jon was talking about.
 
yeah... its not all diamonds... just very coarse ones that are electrically plated onto a metal surface... they dont move around like ones in slurrys and pastes, have more exposed surface area, and cut much deeper because of it. This can cause stress fractures in some cases and in some steels. Most other diamond uses are totally fine.
 
I don't use them on everything, but I've been pretty happy with the results of Dmt fine and extra fine "stones" on Aeb-l and m390. I did 2 identical scimitars for my butcher, finished one on a 2k Green brick and one on the Dmt 8k (xf). He picked up both knives and felt the edges, looked at me and said , "this one doesn't feel like your sharpening" like it was dull. I just told him to try it on something. Then he chuckled. It was finished on the Dmt, too refined for his taste on that kind of steel , but very easy to use. I'll try the fine Dmt for him next time.
 
Years ago Murray Carter questioned me about my use of the DMT XXC plate for initial edge creation. He wasn't fond of the idea and mentioned how he believed that diamond plates had the ability to damage an edge. I listened but honestly I blew him off and kept using diamond plates on my edges. Then about a year or so later I had a couple of bad incidents that made me re-think the diamond plate thing.

What happened in both cases (gyuto & yanagiba) is that the edge chipped out right on the plate while I was working up a burr. As I recall the gyuto actually made a sort of ping sound when things went south. :bigeek:

Back then I had a little USB microscope set up so I took a look at the damage trying to figure out what happened, looking for a clue, as I was puzzled. I did have Murray's words creeping into the back of my mind right about this time too. What I saw in both instances (done at different times) was that there were deep grooves cut in on both sides that lined up perfectly to make the edge so thin in that one exact spot that it fractured. At first I wasn't sure what I was seeing, on the yanagiba, but when the gyuto happened just like a month or so later I was pretty sure what was going on. In my opinion, it was the combination of the DMT XXC 120x plate, the thin hard edge, and too much pressure being exerted by myself that caused the perfect storm to go down.

So I quit using diamond plates on edges and I've never had this happen to me since.

Lesson here? Don't use really XX coarse diamond plates on Japanese knife edges. I think one of less coarse models would be OK as long as you're not leaning super hard on it. The XXC DMT is bad news for edges, it's just way too aggressive for this task.....oh and Murray was right. :)
 
Lesson here? Don't use really XX coarse diamond plates on Japanese knife edges. I think one of less coarse models would be OK as long as you're not leaning super hard on it. The XXC DMT is bad news for edges, it's just way too aggressive for this task.....

I agree completely...from my own experience. Not in sharpening, but in rough flattening a blade road. I initially wanted to use the two coarser plates to ensure there were no overgrinds along an edge. The XC plate turned out to be more than sufficient. The XXC simply dug gouges into the hardened steel that were a nightmare to get out (rougher than a fresh 36 grit belt). If they do that to a blade flat...I can't imagine what they'd do to a .05mm edge even when simply setting the initial bevels.

I'm still hoping to find a use for it though...I'm just not sure what yet, lol.
 
What is approx. grit on XXC.I use a Atoma 140 to thin behind the edge,mostly on Dull Stainless knives.Then Atoma 600 to take out scratches.Never used finer plates prefer whetstones.Don't like Diamond steels at all,seen too many edges messed up wt. them.

From what you guys are saying esp. fine thin edged Japan blades better not to use diamond plates
 
XXC is 120 grit. Like I said, it leaves a rougher finish than a fresh 36 grit belt.

For sharpening, the EF (1200g), and EEF (8000g) seem to do wonderfully.
 
Thanks for all the information given so far, with the tips given, especially by Pensacola Tiger, I've been able to eliminate the issues that I've had with deburring. I got another set of questions, and I felt that I'd be better off just posting in the same thread as oppose to starting a new one.

My interest in diamond plates has also been piqued though as I'm hoping to sharpen knives for various locations around the town I live in. I will mostly be sharpening house knives, cheap German steels like the white handled Dexters, so I want something that will be quick, effective, and low maintenance for I think the diamond plates fit the bill. I'm really just doing this for practice and fun so I won't be trying to make money off labor, but I would at least like to pay for the stones that I'll be using. I'm currently looking at using the DMT XC, Coarse, Fine, and Extra Fine as my setup as I feel like these plate will roughly correspond to a set of waterstones with 220, 350, 600, and 1200 grit. I feel that the really coarse grits will be necessary as many house knives I've felt (3 finger test and finger nail test) are in rather poor conditions, and I believe that the 1200 grit will get a sufficient edge for most kitchen use, especially given the abuse that these knives will be getting. If anyone can confirm my hypothesis or offer any opinion on the matter, I'd greatly appreciate it. Also, can anyone tell me why Atoma plates are more expensive than DMT stones?

My new set of questions:

1. What are the differences between a hard and soft waterstone, and what causes a waterstone to cut faster or slow?

I'm assuming that harder waterstones will dish less but release material at a slower rate, thus slowing down how quickly they cut. However, I feel like that soft waterstones don't necessarily cut quickly, so I guess I'm just kind of confused. An addition to the question 1 would be how does the waterstone's characteristics affect the type of polish the knife gets? I've seen videos where Jon mentions how certain waterstones leave a misty, almost mirror-like finish, and from the way he talks about it, it seems like this type of finish is more dependent on the characteristics of the waterstone rather than the grit (assuming we're discussing high grit stones like 8000+).

2. In order to achieve a consistent bevel across the entire knife edge, do I need to lower the spine as get closer to sharpening the tip.

I'm basing this assumption off basic trig with the assumptions that r=length of blade face, y=distance between the stone and the spine of the blade, and inverse sin of theta (angle of sharpening)=y/r which means that if I want the angle of sharpening to remain constant, I need to decrease y as r decreases so that the ratio between y and r remains constant. I know that the tip is sometimes sharpened differently than the heel or other regions of the knives as it tends to be thinner, but I'm just curious about this. I probably won't be paying much attention to this math stuff as I sharpen to be honest as I hope to just stick with knives that already have proper bevels and shinogi lines set so that I can avoid this hassle. As of right now though, I'm still working on thinning this Artifex to get more practice with thinning and possibly blending bevels, and I'd like to see if my theory makes sense to anyone.

3. Do stainless steel knives have better edge retention than carbon knives when the knives are mostly being used on acidic foods like fruits? What if they're mostly used on non acidic foods?

I've read from some people that carbon knives are suppose to have better edge retention, but I don't believe that this is always true. I do believe that carbon knives are easier to maintain as they're much easier to sharpen, and they do take a better edge than most stainless knives. However, I feel like if I was using a knife mostly on fruits, like a small paring knife, then stainless knife would have better edge retention due to the acid corroding the edge of a carbon knife, but perhaps this corrosion can be negate by frequent wiping of the knife with a wet towel.

4. How does sharpening and thinning a cladded or san-mai knife work?

It seems like the outer steel would sharpen at a different rate than the core steel so how does this affect the way the knife is sharpened and thinner?

5. How do boning knives like deba or honesuki avoid chipping, or are they suppose to just chip with regular use? Does the heavy asymmetry of the knife allow it to glide across bones as oppose to scraping against them? I know I'm not suppose to be scrapping the knife against bones, but it seems like some contact with bones would be inevitable as I try to strip the meat off.
 
Back
Top