Hi huffmnd,
In this forum, scroll down to a post that is dated 11/1/06. The member who posted is fsperry, it has 82 repiles and 10,720 hits.
Its about 7 pages long and you'll find a lot of information about everything from ideas on how to build your own tumbler to pictures of professionally made ones , RPMS are discussed, it covers a lot of ground. Its long, but read through it until you hit the end.
If you have more questions, just add them to this post.
stinger