Sharp enough to push-cut ?

GK mon ami,

Yes, you should be able to achieve "push cut" with either knife.  The "Canadian" particularly, can be made very sharp.

Regards,
BDL

Of course you can! A good sharpener and a honer are all you need. Any sharpner will work, mine is a simple oil stone. Honer (steel or ceramic) doesn't sharpen, only hones.

I feel that sharpening techniques which use the burr as the metric for making a sharp, fresh edge are the easiest to learn and as good as any other for sharpening quality.  I'm also big on the "magic marker trick" for learning to profile and sharpen.  And speaking of profiling, it's very likely that your knives will need at least a little.

When you research techniques of using benchstones, you'll run across the idea of "angle guides."  They're tricky and somewhat counter-productive on longer knives, so I recommend NOT using them, but using other methods to set your angle.  We can talk about some of them if you like.    

Fortunately your English is strong enough that the following sites should help you with your homework.  After you read all of them, post your questions here and we can discuss them. 

Take a look at these (preferably in this order):

Fred's Essay, at Foodie Forums -- a good beginning;

Joe Talmadge's FAQ -- You'll want to look at parts 1, 2, and 3;

Steve Botoroff on Sharpening -- Especially Chapter 3; and the most helpful FAQ of all,

Chad Ward at EGullet

Using a "steel" or "rod hone" is a related subject but not quite the same thing.  Your two knives will definitely benefit from regular steeling.  If you like we can get into how to use them and what to buy later.

BDL

I learned to sharpen from Talmadge's FAQ. I learned angle control from the Sharpmaker, which sounds counter intuitive but I learned what the angles I use the most look like.  Those two took me a long way.

I learned convex stropping technique from Mike Stewart who makes knives at Bark River Knife and Tool. 

When I want a scary sharp durable edge, i convex sharpen. Most of my kitchen sharpening is done freehand on a heavily swarfed diamond stone with a leather strop finish. And while I can get a knife to push cut on that stone and strop, I dont' have any kitchen knives with steel that will hold that edge very long.

This: http://www.edgeproinc.com/ puts a 15° single bevel edge on my Global sashimi knife, as well as 15° and 20° double-bevel edges on my chef's knives and cleavers.

Note that unlike most of the others I've seen, this jig actually only maintains the angle of the sharpening stones. The knife is completely free to move, so you can sharpen any size blade.

That said, I've watched the sushi chef at a local place sharpen his with nothing more than a couple of stones and a tub of water. However I don't seem to have the manual coordination needed to maintain a 15° angle all the way across a 12" blade.

Terry

Truly push cutting a tomato isn't an easy task, as evidenced by the recent "Sharpening Olympics" over at KF.  Five skilled sharpeners each sharpened a carbon Kikuichi sujihiki, and one of the tests was push cutting a tomato with absolutely no drawing, just pushing.  Not one of them successfully accomplished this, including the winning knife sharpened by some obscure guy named "Murray Carter."  Of course, to be fair, one condition of the contest was that the geometry of the knife not be altered; obviously this made things more difficult.  I've seen videos of CDawg (iirc) push cutting tomatoes with a thinned Hattori KD...

The symmetry or lack thereof doesn't really make that much of a difference per se.  It has more to do with the included angle (ie. the sum of the left and right sides).  As an example, a knife could theoretically be ground 0 degrees on one side and 45 degrees on the other- a 0/100 % ratio but it would be as obtuse as a German chef's knife (typically around 22.5 degrees per side).  To push cut a tomato you need a sharp, thin edge.

The Olympics required the sharpener to maintain the factory angles, with deductions for deviation.  Not for any particular reason, it was just a criterion they decided one. 

Sure, if it was thin.  And sharp, naturally!  No, the contest there didn't put much premium on durability, save one point there the judge whacked each knife on a cutting to board to see if the edge would roll.  Although that didn't turn out to be much of a test...in a weird twist, some of the knives where judged to push cut better after being whacked on the cutting board (!).  No, the test wasn't really long enough to determine how durable the edge would be.

Sheesh, I'm dense.  I just noticed the vid you posted was by "SaltyDog", the same guy who did the push-cuts with the KD.  CDawg (who I mistakenly credited) is another frequent forum poster and the guy who took 2nd in the Sharpening Olympics.  My apologies for mixing the two up...two (too) many Dawgs!

While not the edge for all of the Olympic events, might not a somewhat toothy edge push cut a tomato better than a high polish edge? I'm thinking the  sort of micro serrations and steel filaments might do a better job of initially penetrating the skin allowing the edge to do the rest of the work? 

Push cutting means no sawing motion, so serration -- whether "micro," "somewhat toothy," or "like a steak knife" don't help.  In fact serration is counter-productive. 

That said, most people (who don't have sharp knives) cut tomatoes by sawing at them, and prefer serrated to fine edged knives.  Indeed, typical "tomato knives" are serrated.

BDL

I know what you're saying but half the battle in that tomato test is violating skin integrity. I'll have to play around more this summer with tomatoes and edges.

Phil,

It's a test of sharpness, not a particularly efficient way of cutting tomatoes.  The goal is to get a knife to "fall through" a tomato using a "no pressure" "push cut."  That is, the knife is sufficiently sharp that the weight of the blade is enough to make the cut.  Another way of making the test is by dropping a tomato onto the knife edge from a couple of inches above it. 

When it comes to actually slicing tomatoes, even when using an extremely sharp knife I employ a little bit of draw to the cut.  I guess you'd say it's somewhere between a push and a slice.  But that's me. 

Again with the testing:  If a fine edged knife (that is, non-serrated) can't cut cleanly through a tomato skin with very little effort the knife needs sharpening.  There are only a very few things as revealing. 

BDL

Yeah, a little bit of draw to break the skin, then push.  It does take an extreme edge to "fall thru" a tomato under the weight of the knife. 

I actually do that with everything I cut lately. I have also been switching between a Gyuto/ Chinese Cleaver/ Santoku/ German Chef for prep work, so it might just be that it is the most effective and universal techinique.