First off, let me say I am new so my wording may be different than what you are used to. I am attempting to build my first CNC and I am wondering what a good spindle speed would be. I am more looking what the max would need to be since I am going to make it adjustable. I would like to be able to cut plastic, wood, and metal. I have used CNCs before but don't remember all the details.

Good amount of people use variable speed router. With Hitachi that i have you get 8000-24000rpm.