I'll take a "stab" at this one.

Consider a spear. Why does the spear end in a sharp point, rather than the rounded butt of a broom handle? The answer is that the point serves to concentrate the energy behind the spear into a very small area. The same is true of a needle. If you rest the tip of a needle against your skin, hardly any pressure is needed in order for it to pierce. A matchstick, however—-roughly the same size and weight as your average needle—-will simply press comfortably against your skin with the same pressure.

The edge of a knife achieves its sharpness in precisely this manner. The clean, straight edge of a knife is actually made up of a series of microscopic serrations. This line of tiny points serves to concentrate the force behind the blade into an extremely small area, allowing the material being cut to part to either side. This is a cut at its most basic level.

As a knife gets used, these teeth can sometimes be broken off or bent out of line. This what we usually experience as the first few stages of dulling, and the result is that the force is distributed over a larger area. Honing (e.g. with the rod that comes with most sets of kitchen knives) basically serves to coax these micro-serrations back into alignment.

(Note: There is a difference between using a hone and sharpening a knife. The hone, as described above, re-aligns those micro serrations. Sharpening, on the other hand, produces a new set of micro serrations by process of abrasion. The abrasive action of the hone--if any--is very slight. Thus once a knife has dulled much at all, the hone will no longer be effective.)

Now, addressing your question. I believe that the reason for a "slicing" stroke vs. a "drawing" stroke is actually because the drawing stroke can produce an edge that is a little bit TOO fine. With a drawing stroke, imagine zooming way in on these microserrations. As you draw the blade along the hone, friction against the steel will be pulling those teeth out, away from the edge. At the scale that we're talking about, the metal is quite malleable, and that friction can do one (or both) of two undesirable things as a result: 1) if the angle of the edge relative to the hone is even slightly too steep, the teeth can be caused to flex and roll up, away from the rod, producing what we call a "wire edge." Then when you go to the other side, this wire edge will often break off entirely, leaving you with a knife that might still cut alright, but won't be quite as sharp as you'd like. The other possibility is 2) The friction against the steel will actually cause the micro serrations to stretch and elongate. This result can produce a keener edge than you might expect, but it is also MUCH more fragile, and the knife will dull more quickly (as described above).

That's the way I understand it.

Zack

That was a very good dissertation right there.

This is a video of Master Smith Bob Kramer demonstrating and describing the techniques for how to use a steel to sharpen a knife.

[media] http://www.youtube.com/watch?v=MUdrRE7W0b4 [/media]

"Steels" come in a variety of "cuts" some are completely polished and smooth and some have what are called double cuts with length wise grooves and circumferential grooves not unlike a double cut file. Depending on the "cut" the steel will give different results. The "steel" serves two purposes, 1. to realign the edge, 2.generate new teeth or micro serrations (if it has a "cut" on the surface the "steel"). A packing house "steel" has no "cut" whatsoever and is meant to simply realign the edge. This is used in a situation where the knives are getting a razor edge put on them on a regular basis ( twice a day in some packing houses). When a knife with a smooth polished edge hits a bone or the conveyor belt the edge may deflect and become out of alignment and therefore will not cut as efficiently. A polished steel will realign the edge without roughing it up and so keeps the razor edge which allows for a push cut, much more efficient that a slicing cut. The same thing happens over time when your blade hits the cutting board time after time.

Most "steels" have a linear lengthwise "cut " to them and are usually referred to as regular cut steels. Think of this as a linear file as the "steel" is made from W5 and is hardened to approx 68HRC and the chrome coat brings it to approximately 72HRC on the surface. So between the increased pressure from the round steel with grooves and the higher hardness of the "steel" you can now see why the "steel" can cut into the edge of a blade. The more aggressive the cut to the "steel" the more pronounced the teeth will be. If the edge of the knife has been ground or sharpened to a very thin edge it may have more of a tendency to roll to one side or the other. If the edge is rolled more that about 25 degrees and you press the edge in to a "steel" you may collapse the edge whereas if you "back steel" the edge you will straighten the edge.

"Steels" with a cut to them will wear over time even though they are much harder than the knife edge and will leave less and less teeth on the edge of the blade and so become more like a packing house steel. Understanding what is going with the edge of your blade when you apply it to a steel can extend the life of your edge and the edge of your knife for a long time.

Bob,

Thanks for the excellent explanation of the difference between steels!!

Gentlemen,

I'll touch this subject, Some things to look at. Coming from 10 yrs. in the meat industry and having a friend that has been at it in an industrial sense (30 years working at Farmlands a major pork producer). Not all steels are created equal.

For most folks they are using steels from their butch block. Which I've found are way to coarse. To ceramic steels which are way to fine. In a nut shell some steels are to coarse, almost like a file, to too fine.

The same could be said as in the steel of the blade. I've owned dozens of steels, but always the same knife steel (material in the blade). I've found some sharpening steels to work better than others. I've seen other meat cutters running 400 grit sand paper down their sharpening steels, to create a finer surface, saying this is the only way to treat a steel. (From here on out steel refers to the rod use for sharpening).

As far as steels go. You can purchase steels made of ceramic to diamond and steel (metal). I've found the smooth steels and ceramic to be way to smooth (saying that the edge you already have is micro fine). These will work good, but you have to have a really good edge to start with. A diamond steel will actually put remove material with given pressure to a fine edge.

This is an interesting subject. Most knives I've used in the meat cutting industry have a really fine cutting edge as compared to the thicker edge that is put on most custom made knives. Day in and day out in the meat industry we used a thin blade such as a fillet knife as compared to thickness of standard hunting knife from a maker.

Three things that can be seen from this discussion is edge thickness, steel used in blade and the type of steel. I'd would not be comfortable in giving an answer until I knew the type of sharpening steel used.

Dave from Diller

Companies are now making coarse ceramic steels. I purchased one recently, thinking it would be "fine" only to discover it was aprox 400grit. Way too coarse for my needs.

There are so many ways to skin this cat, Bob pretty much coved steels. I am a full time maker of chef knives and deal with many professional chefs, they end to use steels out of the necessity for speed. These guys are moving so fast they do not have time to stop and sharpen they're knives until after hours. These same edges can be acquired many different ways dependent on the material you are cutting you may prefer different edges.

Example:

1) When cutting slick skinned foods such as tomatoes. I prefer a fine tooth on the edge. This will grab the skin then cut . For this I use very fine stones for sharpening.

2) For cutting sticky foods like meats, i like a smooth polished edge. For this I will come off the fine stone and go to a strop for the final edge. This will give you a "hair popping edge."

Example 2 is more likely what you are achieving when you pull the knife backward on your steel. If it is a packing steel or worn down steel, you are stropping the edge.

Steve W.,

Excellent notes. I'm sure that you had the same results from the ceramic steels both forward and backward strokes.

My next thought would be on edge thickness. A thick blade will tend to led to a higher angle on the steel to touch the cutting edge where as thinner blades will have less of an angle.

If we look at the question asked we are posed with steel type (type of hone), steal type (meaning metal) and edge thickness. We have yet to cover whether to draw toward the person or away.

I will agree on pressure though. With even a coarse steel the lighter the pressure the more it is actually like stropping.

Dave from Diller

One thing that has always caught my attention is watching chefs hold the steel out in front of them and draw the blade across it in a very rapid (almost slapping)motion. In almost twenty years working in kitchens this is almost always how I see chef's hone their knives. The same chef will very carefully sharpen on a whet stone, paying close attention to angle and pressure, but when it comes to honing he is almost slapping the knife against the steel as quickly as he can. Having handled some of these knifes I would say that their improper use of the steel is likely doing more harm than good.

The first thing I would recommend is bracing the end of the steel on the table, this keeps it steady allowing proper angle and pressure. The second thing I would recommend is going slowly and lightly. You wouldn't carelessly slap the knife onto a whet stone, why would you on a steel? I prefer a diamond steel, after ten years of use the surface is very smooth and leaves a razor finish. It does remove some steel from the edge, but this way I don't ever have to use a whet stone and my knife is always sharp.

Oh, and I spray the steel with spic&span to lubricate and I push into the edge.

After spending nearing 26 years skinning and using a steel, I will have to agree not all steels are created equal. It is also quite amazing how everyone with evolve their own technique. I use a motion that both slices and draws the steel. It helps me find the steel and gauge my angle with the blade. My dad has his own style and it is different from mine. What is even stranger is that if I pick up one of his knives and try to sharpen in on a steel it will not sharpen because of the difference in the angle each of us uses.

I have a set of oil stones, diamond plates and waterstones that I have learned to use and try to pick one that is better than the other. I have also used steels and leather stromps to finish with. In the experimenting I have done over the years, blades can be made as sharp as one could want woth any method. With a steel if used enough you can feel and see the "feather" of the edge move and come off.

Newer made steels seem to not work as well as the older steels I have used. I cannot give a reason other than I feel many new steels are too course and the older steels have been worn to a finish that works for me. Heck I have used the spine of knife as a steel if I could find nothing else and have been surprised at the results.

Thanks to all who have posted on this subject. I am finally understanding what my grandfather was trying to explain on the quality of the "steel" that he was approving of. He seemed to favor a finer finish. He was a meatcutter in the 20's and 30's and did a bit on his farm in later years. I also see the chefs seemingly whacking their knives on the "steels" and not running the entire edge of the knife. I always wondered if this was perhaps incorrect...