Just a thought. I've made a living with these tools years ago. Air die grinders are ok if you aren't trying to do anything intricate. The hose inhibits precise movement. It's ok for hogging something out with a coarse carbide tool.
For fussy work, I personally use an electric model. That includes cylinder head work, deburring etc. I do have an air model but rarely use it. Don't like the noise for one thing.
Just my opinion
Al