Knife Sharpening Dilemma - I'm not alone

[banewf]

I'm hoping Jeff will respond directly to this.

After my wife berated me for ruining her knifes I went to the forum and discovered that what I'd done appears to be a relatively common problem. Despite my best efforts I had successfully added a concave shape into the blade of the knives (2 in particular). While I'm pretty good at maintaining a consistent angle along the length of the blade I'm useless at keeping the original "straight' shape of the blade. I've had the Tormek a little over a year so am still on the learning curve. 

While I find the T7 is great at maintaining my turning tools I justified the expense of the system by offsetting the cost of sending the knives out to be professionally sharpened. So as you can guess, this recent development has me in the dog house and I'm searching for some guidance. I imagine I'll be sending the knives out to correct the problem I caused but I want to know how to maintain them once we get them back.

Knives that have thicker blades I seem to have no trouble with. Knives with thinner blades have suffered under my hands though: one chef's knife (6" blade) and one paring knife (4" blade).

The stone has been trued up and prepped to grind at the fine coarseness. Since the problem does not occur with every knife it means the cause is either the style of knife (type of steel, length and flex of blade, etc) or the user. As for the latter: am I using too much pressure, should I simply "hold" the knife holder square to the stone and let the tool do the work? how much pressure is right? Does it make a difference where along the blade the holder is attached? should it be in the middle, towards the tip or towards the handle? Suspiciously, the concave portion appears in the portion of the blade where the holder is attached (basically the middle). Coincidence - or does the holder somehow change how the blade is presented to the stone?

Jeff, as you are the 'star' of the instructional videos and this, in my opinion, appears to be a common issue, would it make sense to update or add a video that touches on these finer points:  where to position the holder, how much pressure to use, how to insure you consistently maintain the original shape of the blade?

For anyone else who (hopefully) has overcome this dilemma please free to comment - I welcome the help.

Sign me - lonely in the dog house

[Ken S]

Bryan,

I suggest you purchase a "good enough" knife (or a couple of various sizes).  You don't want to learn the trade with our wife's prized Henckels. (Her favorite chef's knife would not really be make nice paring knife!) With the good enough knife you can develop some finesse with shaping the edge.  Hopefully this will help you relocate.

Good luck and keep posting,

Ken

[Herman Trivilino]

Well, it sounds to me like you have the skills to fix the problem yourself.  Just spend more time on the places you need to so that the convex shape is restored.  You are right in that the thinner the knife the easier it is to grind away and change the shape.

One thing I learned from Jeff was to prepare the grindstone to the fine grit when sharpening knives.  You need the coarse grit only if the knife is really dull or has damage such as nicks.

If you prepare the grindstone coarse it will eat away a thin knife rather quickly.

[Ken S]

Bryan,

Stig (listed as Stickan), our contact person with Tormek AB in Sweden, posted a couple items which might interest you:

The first answered the question about a knife not cutting green onions due to a hollow spot on the blade curve.

"« on: August 12, 2013, 08:36:12 am »
"Any light shining through between the edge and the cutting board indicates a hollow spot in the blade.  That part of the blade will not cut completely; things like green onions will not be cut through."

Use less time and pressure in the middle of the blade. Requires some practise but then the edge will have a perfect line."

Dealing with knives whose blade curve has concave spots should be part of the enlarged "troubleshooting" you tubes.  It is a common problem. it does not reflect an shortcoming with the Tormek. It can certainly be corrected by a skilled Tormek operator. The trick is to be aware of the situation and deal with it.

Stig's second quote is one of those posts which strikes me as good sense.

"I'm a knife nut too and have some nice chef knives and we have rules at our home how to treat the more expensive knives 

Never in the dishwasher, always hand wash, dry them and hang them on a magnetic holder.
If you have a wood block to have your knives in, put the knives in on their backside.
Always use the backside when removing meat/salad and such from the cutting board."

I have always fastidiously hand washed my kitchen knives and kept them in a wood block. I now place them on their backs in the block, although, I confess, not until I noticed the edges had cut into the block.
Thanks, Stig, for the third trick.  I do most of the chopping in our kitchen.  It never occurred to me to flip the knife over and use the back for removing items from the cutting board.

In the spirit of adding something when using another person's good idea, I scoop the chopped vegetables into a flat plastic scoop. It was not expensive ($5 US), and is very handy.  I think these plastic scoops would be a very good item for anyone with a knife sharpening service to have available for purchase.  They are a genuinely useful kitchen tool for one's customers and a source of extra revenue.

Herman is "spot on", as those on the far side of the pond say, about using the stone graded fine most of the time for knives. Proceed slowly.  It is easier to subtract than to add to a knife!

Ken

ps You will soon discover we have fun on this forum with the language variations between those of us who speak the proper (American) English and those who just speak English. It makes for good humor and camaraderie.

[SharpenADullWitt]

While there are two jigs (longer one for flexible knives), there was something that stuck with me, in both Jeff's video and a hand sharpening of Japanese knives, video I have seen. 
Jeff's video:  https://www.youtube.com/watch?v=fYURcwkKGPs
hand video:  https://www.youtube.com/watch?v=SIw5ChGOADE

On the second video around 4:58 he starts to talk about their device (in a little more explanation then Jeff gives).  I expect this might be an issue, something to look at.
Keep the jig front and the blade edge, parallel.

[Rob]

those of us who speak the proper (American) English and those who just speak English.

e230r[8w4r[03j4t0u340t v30ti34i-2i3-i2-wir-i-wr-#';!"£$%^&&*....EXCUSE ME....it gets me right...right....right there when he says that :-)

[Ken S]

Good post, Rob.  I picked up two good tips from Mr. Tsuchida's video. (make that three, the importance of the "powder" in the sharpening process.) The first was the change in sound when the bevel angle changed. I will pay more attention to that in the future.

The second tip was to keep the angle setter parallel to the sharp side of the knife, not the back. Of course, Jeff also covers it in his video.  As much as I have watched Jeff's videos, it never mentally clicked with me.  I probably set the knife that way; it just hadn't entered my conscious data base. I like pairing the two videos.

As per Jeff's video, I must also remember to skew the knife on the leather honing wheel. There is benefit in refresher training.

Jeff made a funny post about his traveling chisel sets which also applies to knives.  Looking at his chisel set, the thing which stands out is the very short chisel in the middle.  That's the one he normally uses in demonstrations.  We are so concerned with preserving the steel in our precious kitchen knives that we rarely practice enough to become really proficient. We have knives almost the original size which aren't quite sharp.  Jeff has created many very sharp "paring knives from chef's knives" (an old expression relating to the large wet grinding wheels of years ago).  Part of our training should be acquiring "good enough knives" for frequent practice.

Ken

ps Your last comment would be quite readable in New Jersey, where I spent my childhood, if you changed the "ti" to "di".  The "ti" must be a local Yorkshire dialect.

[SharpenADullWitt]

I caught that trick pretty quick. (it STUCK out at me)  I have a horrible quality, cheap cheap, college student type of chef's knife, that I want to sacrifice in practicing the bad, then the good method of keeping with the blade.  If I hadn't caught it in Jeff's video, I would have been guilty and kept it with the back.  (so I want to prove to myself the results)

I thought one day that knife would make a scraper.  I think I have a better use.

[Tormek moderator]

You guys have done an admirable job of covering all the salient points, but I think Herman got on to the most important one. Knives hardly ever need the faster cutting action of the grindstone. If your grindstone is graded properly (or alternatively you use the SJ stone) it's relatively difficult to change the profile of a knife.

[Ken S]

I thought this was reviving.

Ken