Stiletto styled gravity knife

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ILikeStilettos
Posts: 1576
Joined: Tue Jan 28, 2014 3:36 pm
Location: Norman, Oklahoma, USA
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Stiletto styled gravity knife

Post by ILikeStilettos »

A Facebook friend, Ray Vitkus, asked me if I had ever looked at a parabolic blade. Honestly, the one problem I had in CAD was creating a pleasing and reasonable curve to profile the blade. My friend, Killbucket, suggested that since I knew where the point was supposed to be and where the edge of the ricasso was supposed to be, then I had only to pick the correct place in between. What he suggested is called an "arc from three points" and it creates a curve of constant radius, then positions it to pass through the three points by geometry. In practice, unless the blade is fairly wide to start, then it gets so thin at the tip that it's fragile and difficult to grind. Since stilettos have typically slender blades, I began to extend the straight edges of the ricasso before starting my arc. Mathematically, a parabola is of constantly changing radius and has the most curvature near the vertex, or in the case of a blade, the point. This is just what the doctor ordered and I found my CAD system was already set up to draw them. Here's my first design with a parabolic blade. (I did extend the ricasso slightly to keep the blade sturdy, but it was just a guess and not nearly the requirement it is with the constant radius approach.)

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I also combined a couple of other ideas that I wanted to explore. Someone had posted a lever operated gravity knife (turn the lever to lift the back spring to release the blade in either direction.) Since I like big knives, I drew it as a 12-3/4" bayonet stiletto with a coffin pommel and kept the top and bottom bolsters the same length. Finally, I took a page from JTK's book and created a fulcrum release more or less built into the front bolster. I noticed on Jeremy's knife that the fulcrum could move through about 150°of arc, so I wanted it to be stowable forward, and then be pulled back to release.

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Lately I'm fascinated with coffin pommels, so I have done that. Since there is no kick spring, the pivot can be located almost vertically centered on the bolster. I figure the knife could be pointed down and then released to fall open without flicking it. It should be nearly silent. The parabolic blade is quite sturdy. Since it has no fire button or sear hole, I was able to use large pins throughout and place them symmetrically. It's not exactly an Italian Stiletto, but there's no mistaking its parentage. It's very clean and no doubt it will cause some folks to ponder a bit while they are trying to figure out how to operate it. As a side note, with very small modification this could be realized as a fully sharpened dagger blade. The blade stows quite deep in the handle and since you don't have to press on it to energize the kicker, even two sharp edges are possible (thought on a 5/32" x 5/8" blade, the angle is too blunt to be very sharp.)

In the open view below, I'm showing the fulcrum rotated to unlock the blade.

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It's quite sleek when closed.

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Finally, I'm showing the external views to give you an idea what it looks like for those who don't worry over internals.

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I have no plans to build immediately, but I'd be delighted to see it if someone cares to.
Dave Sause
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(405) 694-3690

"And you're telling me this because, somehow, I look like I give a shit?"

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JimBrown257
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Joined: Tue Apr 17, 2012 10:50 am
Location: Michigan

Re: Stiletto styled gravity knife

Post by JimBrown257 »

Here is a similar fulcrum to that other one but the two prongs go down much farther. This prevents it from ever bending too far down and getting stuck. Though, you can see the two prongs so I kind of like the one on your knife better. If the guard was bigger and covered the two prongs, it would be perfect.
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