Old Knife, New Edge

Monday, December 20th, ©2010 Marcus Brooks

Some months ago I was careless enough to snap the tip off my trusty Gerber LST-II lockback knife. I’m pinching pennies, so instead of buying a new knife I decided to accept the knife’s new shape and put an edge on it.

My knife’s new outline superficially resembles a kamasu kissaki or “American tanto” blade, but of course its thickness profile is still slightly concave, as before. I left the back edge unsharpened at the point.

Gerber LST-II With Reformed Tip

Gerber LST-II With Reformed Tip, Refined Edge

The new “tip edge” is extremely sharp, and a little bit scary. I worry that it may be more dangerous to handle, particularly when closing the blade. It could easily slice where the original point might only scratch. So far I haven’t got any new cuts, but I have been more cautious than usual with this blade. To be safe, you might prefer grinding a broken tip flat and leaving only one edge sharp.

I find the new two-edge blade rather useful. The sharp-edged angle performs slicing tasks well, and the edged tip works much better than a plain point for occasional carving or gouging tasks, like the one that broke my blade in the first place. (Be careful not to press the blade lock when gouging, or the blade might fold on you!)

Progressive-Angle Sharpening

Progressive-Angle Sharpening

In addition to changing the blade outline, I also tried changing the cross-section of the edge itself, adopting something like a katana sharpening technique (as I understand it). Using my Lansky sharpener, I ground each side at three progressive angles: 17, 20, and 25 degrees, creating a faceted edge. The Lansky clamp and guide system makes this easy. Previously I had been grinding a simple wedge-shaped edge with 17-degree faces. The new profile creates a less acute final edge (50 degrees total, rather than 34), but it cuts about as well (perhaps better, for some things), and it stays sharp much longer.

I think I should mention I have tried only this one set of facet angles. Also I haven’t done any really scientific tests for edge sharpness or durability. In any case, it seems likely that different profiles might work better on blades made with different alloys or processes. In short, your mileage may vary!

I’d like to say a word about the Gerber LST-II. This is my all-time favorite pocket knife, with the possible exception of the original LST. “LST” stands for for “light, strong, tough.” It’s got everything I want in a pocket knife, and nothing I don’t. My first LST-II’s polycarbonate handle cracked, but the replacement that Gerber sent me had a tough glass-filled nylon handle like the original; this seems to be standard now for all LSTs. BTW: my original LSTs never broke; I lost them. I keep my LST-II on a lanyard!

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