Hey Alfie,
congratulations, then you found the right forum, your question was already answered thoroughly.
Note that since a spindle is an induction motor that only runs on three-phase electricity, you always need a VFD, which is an inverter that produces tree-phase electricity with a variable frequency. So if you use the search function, be sure to search for VFD also.
Welcome to the forum!
PS: Here is a post with a lot of links on the topic to start with