Expecting to create a lens from blanks with no polishing stage whatsoever, and only a grinding stage is a ludicrous idea. Trust me, I've done it by hand using blanks I rolled myself from molten glass.

With glass or plastic you will need multiple stages of polishing, with glass you work down to a mixture of crushed-up sea creatures called Cerium, and do that two or three times to give the glass as perfectly smooth a finish as possible...yet even then without serious lensworking equipment the glass will not be as smooth as a cheap projector lens.