Sonja Davison Alex Delzell Engr 45, SRJC Fall 2013

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Evidence confirms that sharp stone knives were being created by prehistoric humans approximately 164,000 years ago. Silcrete stones were heated at around 250-300⁰C for about 5-10 hours. This made them harder and more brittle, allowing the rocks to be chipped and flaked into a blade.

Bronze Age: Use of copper alloy bronze to create strong blades; some of these blades, like the one shown here, still have an incredibly sharp edge with the ability to cut.

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Iron Age: Blades become more sophisticated with incorporation of steel; Japanese master the art of making the katana, or samurai sword. The strength and efficiency of these swords can be attributed to the manufacture process, in which multiple layers of steels with varying carbon content are folded over eachother and then drawn, thus removing as much impurity as possible and evenly distribute the carbon content.

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Knives can now be mass produced with utmost precision and accuracy; a number of profiles can be expertly cut to whatever preference or use. Cheaper knives tend to be stamped, while more expensive ones are forged

• Kershaw Chef’s Kitchen Knife: Notable knife-making company; made from AUS6A high-carbon, stainless steel

• Cold Steel Non-Metallic Covert Skean Dhu Combat Knife: No metal except for the key ring; made of Grivory (Polyphthalamide), a thermoplastic synthetic resin which is a member of the nylon family and has a semicrystalline structure • On Ebay right now with a current bid of $2.25!

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Company called Victorinox now making a pocket knife with interchangeable bodies, including small blade/screwdriver set combo, and a 1TB SSD  Price???  Between $2500-$3500…

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Good knives are often made of non-stainless steel (carbon steel), which gives a good edge fairly quickly, but care should be taken so they will not rust. Carbon steel knives are easy to sharpen at home but need vigilance to prevent rusting. Stainless steel is what many cheap modern knife blades are made of, but they often tend to go blunt quickly and take a very long time to sharpen again. Aim to purchase high-carbon stainless steel knives; they require sharpening but they won't rust. With less carbon content than rust-prone older carbon steel knives, these ones hold their edge better and are harder. If you're on a budget, an inexpensive stainless steel is a good choice until you can afford a high-carbon stainless steel knife. Forged blades are better than stamped ones because the forging renders the metal stronger. Avoid knives that claim to never need sharpening. They are not very sharp to begin with and they cannot be sharpened, meaning that when they lose their edge (and they will), they have to be disposed of. -http://www.wikihow.com/Select-Quality-Kitchen-Knives

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Pr440C was the first generally accepted knife makers' stainless and remains quite popular, particularly since the sub-zero process was developed to add toughness. On the grinder, it's gummy and gets hot fast, but it cuts a lot faster and easier than any of the carbon steels. Your belts will cut about 2 to 3 times as much 440-C than 0-1. Using hand hacksaws on it will wear out a lot of blades in a hurry. But with the proper care, good heat treating and finishing, 440C produces an excellent, serviceable and durable knife, even for the new knife maker. Anneals at very low temperature. Please note that 440A and 440B are similar alloys, often confused with 440C, but not worth a damn for knife making use. Commercial knife companies often mark blades 440 when they're one of the less desirable versions, giving the real stuff a bad name. 440C is also available in more sizes and in more places than just about any stainless alloy suitable for knives. It is also essential to remember that collectors hate to see one of their prizes turn brown in the sheath, and 440C handles corrosion resistance very well. While the variation, 440-V doesn't seem to get quite as hard, but holds an edge for much longer and is much more difficult to grind. Above was taken from this sweet website about sharpening knives.

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Took four different blades and cut them up Measured the hardness of each knife Melted each sample into a mold Etched with chemicals Examined the grain structure

• Sample A: Steak Knife taken from Alex’s House • Stainless, China • Sample B: Steak knife “donated” by TGI Friday’s • Brandware, China 55 • Sample C: X-Acto Knife • BLADE?? • Sample D: Dexter Cook’s Style Parer • Proprietary DEXSTEEL stainfree, high carbon steel

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DexSteel™ Dexter’s proprietary, high-carbon, high-alloy stainless steel, that is specially engineered for professional knives. This special blend of elements enhances sharpness, edge holding capabilities, corrosion resistance and ease of resharpening. From Dexter Knives website.

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B D

Melted into mold Sanded Polished Etched: • Ethanol: 95%; Nitric Acid: 5% • Ferric Chloride

C

Rockwell C Hardness: 42/46 Second smallest observed grain size of the blades tested

Rockwell C Hardness: 52/52 Largest observed grain size of blades tested

Hardness: N/A

Blade was too thin to get an accurate reading; tip indented through the blade and measured the hardness of the mount on machine. No grains detected

Rockwell C Hardness: 54/53 Smallest observed grain size of the blades tested

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Balance of hardness and corrosion resistance. This is why stainless steel is the most common material used. Holds a nice edge and is still easy to sharpen. Extremely hard materials are not acceptable for kitchen knife making. DexSteel was the highest carbon. It was also a kitchen knife with no serration. The serrated knives didn’t need to hold the same kind of edge as the chefs knife.

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There was not a huge difference in rockwell hardness between the blades but when we analyzed the different grains of the high carbon stainless steel knife verse the cheap stainless steel knives we could see a big difference. The high carbon had much smaller grains which makes it a harder knife. The high carbon holds a edge much better while the regular stainless is cheaper.

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Thank you to Younes for his help in the polishing and etching process!

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Thank you to our assistant for her support!

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http://www.newscientist.com/article/dn17604-earliest-firedknives-improved-stone-age-tool-kit.html#.UpwdUOIlg7t http://www.icr.org/article/4912/ http://www.thelocal.se/20080926/14596: http://en.wikipedia.org/wiki/Katana: http://www.ebay.com/itm/Cold-Steel-Non-Metallic-CovertSkean-Dhu-Combat-Knife-/151175502754