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Yes, If the grit is harder than the steel parts. Although I would think less susceptible than the screw used on the Z axis or the linear bearings used on the other axis. The rollers would tend to push the grit away rather than pull it in. Plastic dust should have no effect. you should keep your machine clean and lubricated anyway.

Also regular steel rods are ok for demonstration but I strongly recommend a true hardened shaft for real use. see my BOM