Turning Archive

Re: HAZARD with CBN wheels

If you are sharpening a few tools each day I don't think you would have much potential for fine metal particles creating a fire potential. The freshly ground metal will quickly oxidize within an hour or two. If you are sharpening a large number of items creating large amounts of fine metal particles then your risk might increase the potential for generating enough heat in a pile of metal particles to start a fire. In the industrial process of milling metals in closed containers they open the container and expose it to the atmosphere which contains oxygen and humidity. The container of ground metal is then sealed for several hours and milled again to allow the surface of the fine metal particles to oxidize making the material safe to work with. Once the metal surface is oxidized the material becomes stable and safe to work with in the open air. Adding a chemical or water to the fine metals would be the only way to accelerate the oxidation process to generate enough heat to ignite the material.

Your other risk would be dry wood dust catching a spark and slowly smoldering until it creates enough heat to start your wood dust and shavings on fire. Dry wood dust is very combustible as it has a large surface area of jagged edges that can catch a spark and ignite quickly. The size and shape of combustible materials determines how easy or quickly it will ignite. Freshly ground metal particles have jagged edges which increases the risk until it is oxidized and covered with a protective layer of oxidation to limit the potential for fire. A spherical metal has a smaller surface area which is a smooth surface reducing the potential for ignition.

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