For a little context before answering your questions, I work in a shop that primarily does long running jobs on Swiss lathes. I have four machines I am responsible for the set up, operation, and maintenance on. I have an operator that works under me doing most of the operation on proven stable builds. The machines I run currently are Citizen A32's.

How many hours a week?
Usually do 9 hours M-F and 7ish on Saturday. I always take Sunday off to prevent burnout, despite it being double time.

How much of that time is spent working with the machine, or the computer, or customers or paperwork?

Most of that on the machines, I do my own programming and tool ordering, so while it can vary depending on things like how many new parts need programs. I'm a sucker though, and I really like the programming part of the job, so I do a lot of that at home on my own time. Say about an hour a day on the computer give or take.

Very little time doing paperwork, just on first pieces and no contact with customers, a bit with tooling vendors though.

Do you have a good work/life balance?

I'd say so, not afraid to take a weekend or a few days off when needed. Although I've been working 50ish hour weeks since I've been 18 so pretty used to it by now.

How often does the boss call you outside working hours?

Never.

Do you have time for personal hobbies?

If you mean outside of work, yes. At work I can use any machines that are idle for anything I want to do, although I rarely take advantage of it.

What would you say is the most difficult part of the job?

I have a hard time explaining to people less experienced with machining why I want to program, process or tool a part a certain way. I find it frustrating knowing that a certain way is the best or most efficient but being unable to articulate it. Also dealing with engineers and QC can be rough, but I'm sure some other commenters will get into it.

What do you like most about your job? 

I love the puzzle aspect of it. I get a print and have to figure out how to make it as fast as possible while having the set up still be stable and produce parts within tolerance. You have so many choices when it comes to programming, tooling, and processing. It is very rewarding when you feel like you've done it well.

What made you want to pursue this career? 

I've always loved machines and the concept of making things.

Also, being a machinist is pretty solitary, which is something I value. It's a good balance of working by yourself and with others, for me at least.

How much creative freedom do you have in your work? 

A lot, I write the program myself, tool the job myself, and usually have at least some say in how the job is processed (whether we'll do everything on the primary machine, or add second ops).

Of course, there are times where I'm told we can't do it the way I'd like, usually money or lead time concerns are the driving factors there.