3D Printed Knife Scale

Wanting learn about the latest self-manufacturing technology known as additive manufacturing or 3D printing, I came up with a project for myself. I decided to use 3D printing to make one of the most popular selling folding knives lighter and have better grip. I achieved this goal by designing and 3D printing a replacement knife scale (handle) for the Kershaw Cryo folding knife.

How I came about this project is that I have a great respect for well designed and useful gadgets, gear and tools. One of the oldest and most useful tools is a good knife. I did some research on what knives where popular and practical for people to carry on a near daily basis. I found a very helpful forum called EDC Forums that discusses everything from flashlights, knives, keys, lighters and everything in between. From my research I found an affordable knife that was one of the top sellers for the year and decided to work with the Kershaw Cryo folding knife. This knife has internal mechanical parts that consist of a spring and some other small parts that assists in the operator in opening the blade quickly and safely. These tiny parts proved to be challenging in designing around them. I could have discarded these parts and lost the assisted opening function but decided to test how far I could push the limits of rapid prototyping materials on my project. I decided to test out laser-sintered nylon and ultra-violet cured acrylic for my materials. I considered buying my own 3D printer but I needed an ultra high resolution printer to make the tiny details in the knife scale to hold the springs and bolts as well as the high end 3D printing materials only capable of being used by multimillion-dollar machines.


Once I had the knife to work around, an objective to achieve and an online 3D printing service picked out I started with the computer design. Before I could begin making the knife handle I measured the existing parts using digital calipers, external micrometers, a digital camera, a flatbed scanner and a digital weight scale. After getting my measurements which proved to be very difficult due to the lack of straight lines on the knife handle I drafted over 40 variations of the knife scale using the software Sketchup Pro. I spent about 120 hours on this from start to finish. Here is the final 3D rendering of the knife scale. Note that the colors are only for visual reference in making it easier to see the surfaces. The colors in the final versions are determined by material selection in printer.



(Exterior of Knife Scale)



(Inside of Knife Scale)


In making my design it was important to lower the weight of the original knife since it was one of the biggest complaints and to add to the grip of the knife since it was very slippery. I lowered the weight by changing the material and increased the grip by adding texture to the handle. I also increased the material thickness of the scale to give a more confident feel in your hand and more to hold on to. The larger width also accommodates for the weaker material choice of space-age plastic over the original metal handle. Here are a few more images of the finished product:


(Purple laser-sintered nylon on left and semi-transparent ultra-violet cured acrylic on right.)



The end product came out meeting my expectations and has proven to be durable over the several months of testing I have done with it. The added visual styling of the knife really makes it an eye-catcher and the lower weight makes it less noticeable to carry in your pocket.

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