At the risk of sounding like a jerk...
When standing in front of a piece of equipment, your a machinist.
When at the bench, your a gunsmith.
The relationship between the two is symbiant, but they stand alone as very different.
It's important to understand this. As a machinist topics like surface speed, tool geometry, etc become very important. Learning and understanding it will save you a ton of money, time, and aggravation. The volume of resources available can be overwhelming. A great place to start is with a tooling manufacturing catalog. Speed and feed charts are often listed. You bounce that information off the type of material/hardness your working with. In the end you get a set of values that define how you setup a particular job.
"Winging it" may get you a part. It may also get you a work hardened mess or a tool friction welded and broken down inside a hole. (Reboot, thaw out the Visa card, and start over...)
There's a "presence" here that will be inclined to roll eyeballs and summarize what I'm saying as trivial and unnecessary. I'm not out to change the world. YOU asked so I'm talking to YOU. These companies spend billions researching and developing this information. It exists for a reason.
Gunsmithing:
It's tough to source solid information and much of it can only be learned by doing and/or bugging someone who's done it for a long time when questions surface. The real trick is getting them to talk. You must remember that most gunsmiths are mavericks and a bit compartmentalized. Many don't go out of their way to share what they perceive as "the right answer" to building a rifle, pistol, etc. It's a competitive trade and making a dollar is tough.
Good luck on your quest. Read, then get to work. Don't get bogged down in a book or DVD. Experience will never be overshadowed by education.
C.