چرخ زنجیر

Also known as cogwheel, cog, chainring, sprocket-wheel, chainwheel, sprocket wheel

thumb|16 tooth sprocket. Do = Sprocket diameter. Dp = Pitch diameter thumb|A sprocket and roller chain A sprocket, sprocket-wheel or chainwheel is a profiled wheel with teeth that mesh with a chain, rack or other perforated or indented material. The name 'sprocket' applies generally to any wheel upon which radial projections engage a chain passing over it. It is distinguished from a gear in that sprockets are never meshed together directly, and differs from a pulley in that sprockets have teeth and pulleys are smooth except for timing pulleys used with toothed belts.