Why the polished edge (for defense).
I talked to another client last week while I polished a knife that could be used for defense. Like most people, he believed that "sharp was sharp" and "a rough knife rips." These are points I hear everyday.
First, a short refresher course. Unless I re-profile an edge (make it thinner like a barber's razor), I begin by ensuring the bevel is uniform. Remember, most knives are not. If you grab the first knife within your reach you will find that the bevel is wider in some points than in others. The edge is not going straight down the blank.
Once completed--and that's the hard part--I begin by using finer and finer grades of stone, paper, pastes and glaziers' glass to buff out any imperfection. I make a small minor adjustment at the end to lightly buff out any microscopic burrs or imperfections from the edge. Most stones are in the 100 to 200 grit range. I finish at 6000. And while they are pretty to look at, they are no weaker than the original poorly finished edge.
Will a rough, poorly knife cut? Of course. You've seen it yourself. Did you ever watch your no-brother-good-inlaw "saw" through a deer?
For our purposes, a defense knife has to slice--right now, no screwing around.
Here's the urban legend that got me into this thinking.
In 1958, police near San Diego thought organized crime was trying to muscle onto the docks. One morning a cut up body shows up, which they transport to the area coroner. This coroner takes a short glance at the body, and decisively states that the mafia had nothing whatsoever to do with the thug's death.
The officer seems surprised, and asks the coroner about his comment, to which the ME responds, "It was the Yakuza who killed this man. Look at the precision of the slices. You can't get a knife sharpened like that in the United States..."
Coupled with this, many of our modernknives are made from alloys that must be mirror finished. For example, S30V will show micro-chips on the edge (it looks like a tiny string of pearls) unless it is buffed. The alloy VG-10 is great stuff, but a simple buffing will immediately enhance its edge.
Many times here (and in Wisconsin) we cannot carry a firearm. We must decide on contact weapons, be that pepper spray, a kubaton, or a knife.
Other than a cavalry sword deliberately blunt to break bones, close quaters knives are razor sharp and have needle points. For example, the first third of an Emerson CQC-7 is a modern rendition of a Japanese lance.
While I'm not a big fan of many of the Cold Steel products, their tanto series reflects this process. Mirror finish, solid point for thrusting.
History lesson over. I'm an older guy. I probably cannot take the beatings I once endured for the privilege of a cool drink and a hotter companion. Because of professional connections, I can buy, modify, polish and carry any knife made on this planet. My defense knife has a mirror finish.
We put our best ammuntion into our CCW pistols. I advise my clients to think about that same idea with contact weapons.