Review on SPTA Proxxon Aluminum Grinding and Polishing Tool by James Vilchez

I was disappointed in the quality. Some stones are planted askew on the waves. Not suitable for fine work such as sharpening knives. The stone bounces off the blade instead of creating a smooth grinding surface. Stones are good for grinding rough surfaces, but not for fine grinding. Simply roll the stone with your finger on a smooth, hard surface to test it before attempting to use it on anything that needs a fine sanding to avoid damaging the fine surface.