In 1981, legendary knife designer Blackie Collins created the LST (Light, Smooth, Tough) for the equally influential Pete Gerber of Gerber Legendary Blades. Based on Gerber’s best-selling Folding Sportsman I design, the LST was the first conventional lock-blade folding knife to use an injection-molded handle. While the Finnish Hackman Camp Knife, a balisong-style folder rumored to have been issued by the CIA in Vietnam, predated Collins’ design, both the engineering and the material choice of the LST’s handle were considerably more sophisticated. Specifically, the LST pioneered the concept of a one-piece injection-molded folder handle and the use of DuPont Zytel, a glass-filled nylon resin.
[FYI: The first Gerber LST folders were made in 1981, however, they had linerless Micarta handle scales. The first molded handle LST was made in 1983 with DuPont Rynite handles. Zytel was not used until 1985. nb]
Generically known as FRN (fiberglass-reinforced nylon), Zytel offered many advantages as a handle material. It was tough, extremely lightweight, could be made in a rainbow of colors, and could be molded into intricate shapes, forms, and textures to create parts that did not require any subsequent machining. Although the molding process did require a substantial initial investment in tooling, it yielded ready-to-assemble parts far more efficiently and cost effectively than machining them from solid stock. For the cutlery industry, the introduction of FRN handles was a game changer.
While Blackie Collins was making history with injection-molded handles, Spyderco was making its own mark on the industry as the pioneer of clip-carry knives. In 1990, Spyderco founder Sal Glesser integrated the two concepts, creating the first-generation Endura and Delica Lightweight Models and once again revolutionizing the form of the modern folding knife. Using state-of-the-art molding technology at the time, these groundbreaking designs had one-piece FRN handles that included integral, molded clips configured for right-side, tip-up carry. The side opposite the clip also featured their Volcano Grip texture pattern for a secure, non-slip grip. Although the integral clip would later be transcended by more versatile clip options, the original Delica and Endura Lightweights were landmark products for their time and once again set the standard for the knife industry.
NYLON, FRN, AND INJECTION MOLDING
The base element in injection-molded knife handles is nylon. Nylon is a synthetic thermoplastic that was first produced in 1935 by Wallace Carothers, an American chemist working for DuPont. An incredibly versatile material, nylon can be shaped into various forms, including filaments, fibers, films, and sheet stock. While natural nylon is typically off-white, it can also be dyed to achieve virtually any imaginable color.
The production of nylon typically starts with distillation from crude oil, but it can also be produced from biomass. It becomes liquid at its melting point of 220 degrees Celsius (428 degrees Fahrenheit) and, as a true thermoplastic, can be cooled and melted again without significant degradation. This makes it ideal for injection molding applications.
In principle, the injection molding process is simple. First, the base material is heated until it melts into a viscous liquid state. The injection-molding machine, or press, then forces that material into a closed mold—also known as a tool or a die—that defines the shape of the part. Once the material cools sufficiently to revert to a solid form, the mold is opened, and the finished part is extracted. While all this sounds deceptively easy, the technology and the specialized materials behind it are very sophisticated—especially if you are trying to achieve specific performance qualities in the finished part.
In its pure state, nylon is very flexible and will bend before it breaks. While this quality may be desirable for fabrics, rope, webbing, and similar materials, most solid parts have different requirements. For that application, the nylon is often “filled” with glass fibers—typically between 10% and 40%. “Glass-filled” nylon is more rigid and has a much greater tensile strength. Synonymous with FRN, it has long been the standard handle material of Spyderco’s many lightweight models featuring injection-molded handles.
FRCP
Although nylon can be dyed practically any color, in solid parts it is basically an opaque material. When Spyderco began developing the Manix 2 Lightweight about 10 years ago, one of the qualities they wanted to achieve was to make the handle transparent or translucent to highlight its internal mechanism. To do that, they had to find a different injection-moldable material that offered the same advantages as FRN but was clear or translucent.
Working in close cooperation with leading plastics experts, Spyderco chose fiberglass-reinforced copolymer (FRCP) as the best material for the Manix 2 Lightweight project. Copolymers are substances created by chemically combining two or more simple compounds (monomers) into a long chain of molecules. The exact chemistry of this process and the specific molecular structures it creates can be manipulated to combine the desirable qualities of the simple compounds. For example, one compound may offer strength and resistance to weathering and chemicals, but not accept dyes well. When combined with another compound that can be readily dyed, the resulting copolymer offers the best qualities of both.
This was the exact process Spyderco uses to fine-tune the attributes of the FRCP used in the Manix 2 Lightweight’s handle. The result was a lightweight, translucent material that could be injection molded into the handle’s desired shape while still achieving our demanding standards of strength and durability. This groundbreaking achievement was recognized at the 2010 Blade Show and International Cutlery Fair, where the Manix 2 Lightweight earned the “Most Innovative American Design” award.
The injection-molded handle literally revolutionized modern folding knife design. Spyderco is proud to have been one of the pioneers in that effort, and even prouder to continue the evolution of that technology with our broad selection of high-performance, lightweight cutting tools.
Originally appeared in the April 2019 Spyderco byte e-Newsletter.
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