If you are looking for metric sprockets because of the 2mm keyway, you would be better off using SAE chain and sprockets, and getting a 2mm broach and a bushing to match the bore in the SAE sprocket. You can buy an arbor press pretty inexpensively from Northern Tool Supply or Harbor Freight. You can also check a local machine shop on using their arbor press, or another school/team in the area to use theirs. There are limitations of the length of the keyway that is dependent on the length of the bushing. Check in MSC catlogue for these items.
