Advanced Knife Machining WIP, Pointy Fighter

Erin Burke said:
Nathan,
What process did you use to get your cat turd model into CAD?
Erin
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I made measurements with calipers. I then drew a three dimensional curve in CAD based upon those measurements and created datum planes along that curve. Between measurements and eyeballing it I would hold the clay model against the monitor and confirm the overall shapes were basically accurate.

I then sketched cross sections on those datum planes based upon measurements and the appearance of the clay scales at those points. For example, in the center of the scales where your palms are meaty the scales are wider at the top. Down towards your pinky it was the other way around. I captured the essence of the shapes at all those locations with curves without incorporating all the tiny little bumps and crevasses in the clay.

I then created variable section sweeps and surfaces by boundaries that referenced all of this datum geometry to create three dimensional surfaces. This is called advanced surface modeling and it is something I used to do a lot of back when I was primarily involved in just plastic product design. Class A surface modeling with C2 surface continuity is probably a little outside of the scope of this WIP because I don't think this is something that most folks here are really going to get into so I'll leave it at that.

If you're curious, this is a screen dump from my CAD system that shows some of the building blocks (datum curves) I used for surface creation:

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Totally can't wait to see this thing progress. Although I will say seeing everything you put into designing a knife makes me feel like simpleton with a pencil and paper :o
 
Fletch Helical said:
Totally can't wait to see this thing progress. Although I will say seeing everything you put into designing a knife makes me feel like simpleton with a pencil and paper :o
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Naw man, I definitely don't want folks to feel like there is anything wrong doing it the "normal" way. I have a different approach based upon different life experiences, so I approach it from a "different" perspective. That and the nomenclature is different, which probably makes it sound more complicated than it really is.

I wouldn't be able to take this approach if I were only making one or two, but I'm making quite a few at a time.
 
Extremely useful information about the intricacies of handle design. Thank you for sharing your knowledge. I look forward to following this.
 
Must say my first glance of the first post was unimpressed...
However your refinements and taking a serious look at the design changed my mind. Will be an awesome blade when it comes to life.
Clean Elegant Serious
Just my 02s as far as balance points to feel "Alive" in the hand and light is keeping the balance point right where the index finger hits.
Serious fighter designs I've been told have the balance point about a 1/2" in front of the scales. Just about where yours is now.
My personal preference is to close my eyes and handle the finished blade in both the L & R hand. Feel the blade. If it feels like it's hardly there or feels like part of your hand... you nailed it. Just my personal preference.
 
This is great! Thanks for sharing your process. Just wanted to say, I often use 2D vector software like Illustrator to design knives and I find it interesting how drawing with control points on bezier curves, (I guess in your case NURBS for 3D) helps to make appealing knife designs. The curves are balanced and make great "lines" for a knife. Although not necessarily ergonomic.
 
This must be what its like for everyone else on here to read the WIP's normally. Similar to my process, but different.. I rarely work from a physical prototype towards the CAD system, but I like the clay scale shaping. Because I usually allow the CAD to drive the end product, I tend not to end up with many organic shapes and contours (as they don't naturally occur) --something I regret.

I do enjoy the focus on the design aspect though. I've only made one physical knife, and to actually machine it took just a couple of hours. But the HOURS spent tweaking the design..
 
Rhidian said:
This is great! Thanks for sharing your process. Just wanted to say, I often use 2D vector software like Illustrator to design knives and I find it interesting how drawing with control points on bezier curves, (I guess in your case NURBS for 3D) helps to make appealing knife designs. The curves are balanced and make great "lines" for a knife. Although not necessarily ergonomic.
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Man I really love the curve creation tools in Adobe Illustrator, they're top notch. I think that programs like that are a much better choice for knife profile design than things like AutoCAD etc. Your hand doesn't draw in straight lines and constant radius arcs, your hands don't grind or forge that way, and your eyes don't particularly like to look at it either (at least mine don't). A line that is moving along perfectly straight and then instantaneously turns into an arc may be tangent, but the rate of change between the two shapes is instantaneous. This is call a C1 transition. When it is a smooth gradual transition it is said to be C2 curvature continuous, which is way more natural.

Smooth natural lines can be difficult to create in CAD but are easy to draw in Illustrator. Plus you can scan into and print out of Illustrator for real world hands on refinement. And lastly I think you can export DXF out of Illustrator which a water jet service could use.

The ISDX package in the CAD tool I use has curve creation tools that are a little like Illustrator, but I think that Adobe really nailed it the best.
 
Inkscape is working well for me, mainly (as in other programs) due to having caught on to creating curves and lines as paths, then adding/subtracting nodes and using them to modify paths and curves. Being able to zoom in until just the dropped edge curve fills my screen for instance, is GREAT for refining detail. I'm not real advanced, but I can print out nice scaled patterns for fixed and folders and glue them to hard stock for scribing.

But wow, that screen shot you posted of your handle in the software, is mind blowing. A level I'm sure I'll never reach.
 
I am neither a machinist nor a computer wiz. So on both fronts this thread fascinates me.

Thanks for putting this all together Nathan.

-Peter
 
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