Just a note. I am sure I will get beat up over this, but.
An indexer is a rotational axis that rotates from one given degree to another given degree. Most are 1 degree increments, some are 5 degree. So you index to a specified rotation and do machining at that rotation angle, then move to the next rotation. It is not necessarily programmable accept for rotation to the specified angle and a feedrate is not commanded. Machining is not done during rotation.
A Rotary axis is one that is programmable and rotates with a feedrate commanded as machining is being done. This is the popular item in the hobby world.
It is a mistake that even seasoned machinists make. I buy this stuff professionally in industry so I need to be sure of what I am purchasing. If you go to a manufacturer of these devises like Haas and ask for an indexer, they will ask "what increment do you want". If you ask for a rotary axis, they will sell you a rotary axis. Normally, a rotary axis will cost substantially more.
Most people in a hobby environment do not know this and call it an indexer, but in fact it is a rotary axis. There IS a difference.
It's just a pet peeve of mind, sorry.