Matt - CNC stands for "Computer Numerical Control" - essentially, a computer drives stepper motors attached to each of the X-Y-Z axes following a program written in g-code. The computer can cut things with far greater precision than a human being. The radial boiler cutouts on the domes are a good example. While this could certainly be done by hand, cutting a circle/radius requires precise manipulation of both the X and Y axes simultaneously. A good machinist could do it - but I'm not a good machinist. hehehe
Something simple like this could also be done with a hand file and some sandpaper - but my motto is "never use muscles when there's an electric motor that will do the same job."
The rig I bought is from
Sherline[/b][/b], and came with everything needed to get up and running - milling machine, accessories, computer with stepper driver and pre-loaded CNC software, stepper motors already mounted - the works. Total cost was around $3000.00. I later added a CNC lathe, also from Sherline, that uses the same computer, stepper driver, and software, so I didn't have to buy those components a second time. I used the lathe under CNC control to turn these domes.
I originally bought these tools to make #21. More details about them are contained in my NPC #21 Builders Log
Pt. I[/b][/b] and
Pt. II[/b][/b], especially the first couple of pages of Pt. I. As is usually the case, now that I have them, I'm finding other uses for them as well. To me, it was well worth the investment - roughly comparable to an Accucraft live steam K-28, and less than a cab forward. One only needs to buy such tools once, and if one buys good tools, they last a lifetime.
As to Harbor Freight, it wouldn't do what these tools will do. First off, Harbor Freight's is not CNC. Also, when buying machine tools such as these, precision mechanisms are all important for maintaining good work tolerances. Less expensive tools are known for sloppy fits producing large tolerances in the work being produced. Again, a good machinist can compensate for less than stellar tools and produce good work on them, but at a higher cost in man-hours and patience (not to mention knowledge and experience). Like I said, I'm not a good machinist.
Bottom line, you get what you pay for as usual. Much depends upon what you want to do with the tool, how long you expect it to last, and what you're willing to pay. However, your initial goals will probably change as you discover more things you can do with the machine. I learned a long time ago that, for me at least, if I want to buy a power tool, to pay a little more and get a good one. I can't tell you all the tools I've had to buy again because I bought a cheap one up front.
MHO for whatever it's worth.
