I've been doing this since 2003. I might even qualify as the first bone head to attempt this stuff. It's a business model that has taken me 17 years to get "right". Were still working on it.
A 10 year old Haas VF2 or VF3 will fit the bill for 90% of what you'll ever do. It does not take a Makino or Matsura to put guns together. I began with a 1992 Haas VF1. Basically, the machine Moses used to engrave the 10 commandments. That machine made me a great deal of money. A metric shit ton in fact. I ended up donating to the local high school for the tax break.
What you are going to find regardless of what machine you buy is that (x10 if its your first machine) you will grossly underestimate the tooling and work holding requirements. So, budget yourself accordingly. If you pay $50,000.00 for a used machine, then you should be adding 20% to that cost to cover a basic tool package. I cannot overstate that enough. You buy machines and soon you realize that it is the easy part.
Tools, holders, and work holding are what make you gray and consume coffee by the bucket.
Next, your work environment. You want 3 phase power. The machines just work better. Solid-state phase converters can work, but its a band-aid fix, and it's been my experience that the machines get buggy, and your power bill will be absurd. Your shop is another thing to look at. The floor is a big deal with a cnc. If it has cracks or has heaved/sunk on you, do whatever it takes to fix that first or you'll be chasing demons for a long time. Ensure it has the load rating for the machine. Also, make sure you can put the machine somplace where it can breathe. The electronics get hot. They need a clear pathway to fresh air so stuffing it in a corner with the pane 6" off the wall is not where you want to go with this. It'll work for a while this way, then all of the sudden you'll have issues.
Last, software. If you want to do this for a living, then get your head around the idea of sitting in front of a PC and learning to program with a CAM package. Fat fingering code at the control is how you give yourself a stubby finger with nerve damage. Doing this stuff correctly depends on a pathway from design to product. The software does this. If your gunsmithing then a lot of what you do will involve more complex tool paths. If it doesn't, then you don't need or want a CNC mill because all it ends up being is an expensive means of holding the floor down. The complexity is where it's at and to exploit it you need software.
Good luck. It's so worth it IMO. No regrets here.
PS: If your buying used from a dealer, I would make them pull the way covers back so you can look at the maintenance history of the machine. That's a PM that should be done annually. I would also ask for a wireless bar ball test and I'd want to listen to it under power. The spindle is the big thing. A vector drive should be almost vacant of sound below 5,000 rpm. A gearbox machine will be louder just cause the gears are straight cut. Vectors are fine for gunsmithing. Gearbox stuff works better when you are laying the hate on nastier materials.
Machine tool dealers: Know upfront they are worse than a used car salesman and/or strippers. They will lie, cheat, and steal. Just accept it going into this. When they say shit like "it's been a light-duty machine that only cut aluminum" call their ass out and put em on the spot because that is complete bullshit. Aluminum is the HARDEST material on machines. It machines freely yes, but the only way to make money in aluminum parts is by running that machine at its max duty cycle for as long as possible because if you don't, some other shop will and they will take the job from under your feet. Most used machines come from a job shop or manufacturing plant doing a changeover.
Aluminum sucks to try and evacuate from a machine. conveyors and augers struggle with it. If that is the path you are going, then it is worth every single penny to get the best machine you can possibly buy because only a few get this right and they are incredibly expensive. You will try and talk yourself out of it, but understand that if you pay a guy $25/hr to run parts, he's paid to run parts. He's not paid to give the machine a C section every 4 hours because it has snowdrifts of aluminum piled up inside of it. It won't take nearly as long as you think to end upside down on the "cheaper" machine. That comes from experience, lol.
This topic could go on for days, but those are the big ones that jump out ahead of stuff in my mind.
Good luck.
C.
