Sorry for taking so long to respond...I knew my post would end up being pretty lengthy, so I had to mentally prepare for it.    I wrote up a post on HC for FrankCooter just trying to cover the basics of CNC parts, so I figured I'd post that info here in case anybody is interested. 

For your links, personally I'd add two big forums:

www.cnczone.com (the HF of CNC/machining...huge, good for beginners, ask anything you want, etc.)
www.practicalmachinist.com/vb/ (the HC of machining...veterans with a lot of experience, more info per post, tilted a bit more towards industry than hobby work though)

My machine can do about 12" x 12".  Z depends on the bit I'm using and how far I choke up the spindle, but I can easily get any height I'll ever need on it.  Maybe 5"?  Able to cut Foam/wood/plastics/soft metals/PCB.

Anywho, here's the post minus the stuff personally addressed towards Frank:

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Basically you want to determine what materials and what table size you need at minimum.  From there you can narrow down parts/models.


You can go with a pre built model like the Shark, Probotix, etc or you can DIY one yourself.  The level of DIY varies greatly...I went with a pre planned table and I believe Kerry actually designed his table himself.  Going the DIY route allows you to have a table any size you want and also helps with upgrading down the line if you get into it.


For the table, almost all CNCs will either be moving gantry or fixed gantry.  All that's describing is whether the router is moving up and down the y axis or if this is accomplished by moving the table underneath along the y axis.  For an idea of how a fixed gantry works, look at the pics of my CNC.  The spindle can move up and down or right to left along that threaded rod, but moving top to bottom (y axis) is accomplished by moving the table platform along the rod underneath it.  Fixed gantries have increased rigidity which comes in handy for harder to cut materials.  The downside is that it effectively cuts the travel along the y axis in half.  As an example, a moving gantry on my table would do about 24" x 12" whereas my setup only does about 12" x 12".  For my uses I decided I'd rather go with a little more strength.


Another consideration for the table frame is material used.  The entry level stuff is typically made of wood/MDF.  The better tables are made of metal, usually aluminum t slots (8020 I think).  You probably want a metal frame if you're gonna do frequent metal engraving, etc.  The downside is that metal t bars really add up in price.  My table is a hybrid of the two, so it uses milled aluminum pieces to strengthen the most critical points/joints of the table and then MDF for the rest.


The next things to determine are the motors.  The two types of motors are steppers and servos.  Steppers are used in mid/entry machines and servos are used in the more expensive machines.  A wiki will be able to better describe the difference between the two, but essentially steppers take 'steps' and servos are 'smooth'.  I believe the normal stepper motor has 360 steps per revolution, but depending on the type of rod/ballscrew you use a single revolution will only move the axis about 1/6".  Add in the newer stepper drivers that have microstepping (so they can take even less than a full step) and that's 10x the no rmal resolution of the motor.  Overall I think you can get by just fine with that kind of accuracy   Servos are not only smooth in movement, but they also have a built in feedback mechanism so that the motors aren't turning 'blindly'.  However, these are really quite expensive.  Next thing you want to look at when shopping motors is the size/torque.  ebay has motors for pretty cheap but most either don't provide ratings or they're the bottom of the barrel...torque probably won't be that great.  I spent a long time looking up motor comparisons, and most of the guys think Automation Technologies sell the best steppers for the price.  Motor size is listed in in-oz.  Bigger/more powerful ones help with cutting stronger materials and also for moving axis around.  You'd be surprised how heavy one of those spindles is, so asking the motor to lift it vertically along the z axis is a lot.  Many people get 2 normal sized motors for x and y, and get the next size up for the z.  I ended up getting 3 pretty good sized motors, but kinda wish I went a size up for the Z.


Now you need electronics: something to drive the motors and something to communicate with the computer.  If you go the servo route, they come with the motor control.  Steppers don't come with anything, so look for a stepper motor control. Personally, I found SO many positive reviews (actually universal...I've yet to see a negative review) of the Gecko G540 that I just went with that.  It makes things a lot simpler and is quite powerful.  It drives up to 4 axis, communicates with the PC via parallel port, and has a plethora of extra options such as spindle control, 1/10 microstepping, etc.  It also has many users, so troubleshooting/getting set up is easier.  I don't think I took a picture, but basically I have a chassis with the gecko mounted on the back, the switching power supply inside, a power switch and E-Stop on the front, and room for a CPU fan on the back.  I can connect relays to the gecko in the future if I want to, say, switch on the water pump or a vacuum automatically or via software.  Before I forget, most of these setups require a PC with a parallel port on the back (though there are some with USB instead).  It also can't be the add on parellel port found on most parallel port extension cards.  You also need to make sure the parallel cable you use has all the pins connected...a lot of them only have certain pins connected because people typically only use them for printers, but mach3 software uses more pins.


Next you need to decide what you want to cut with.  Most basic setups use a router, and spindles are the next step up.  Routers are cheaper, plug and play, need a custom holder to mount it to the z axis, and are generally recommended for wood.  Spindles are much quieter and are useful between about 10,000-24,000 RPM.  Below that they have too little torque.  A spindle would probably be a good idea if you want to do some aluminum engraving.  Spindles are also more expensive...a legit American or European spindle will cost thousands, but many of the CNC guys use spindles from China that are sold on ebay.  They run maybe $400-800 depending on how much HP you want, and this includes the VFD.  Unlike routers, you can't just plug the spindle into an outlet.  You need to control it with a variable frequency drive to manage speeds.  You need a 240V outlet or 3 phase power if you plan on running one of the more powerful spindles, otherwise they'll trip your breaker.  The VFD takes the AC and powers the spindle while controlling the frequency between 200-400 Hz.  For example, 200 Hz = 12k RPM, 300 Hz = 18k RPM, and 400 Hz = 24k RPM.


The last major element is the computer and software.&n bsp; I bought an old Dell desktop PC off of ebay for cheap since it came with a parallel port and I intend to use that computer for nothing but CNC.  There are three phases on the software front: CAD, CAM, and control software.  CAD software is what you use to draw stuff, either in 2d or 3d.  AutoCAD, TurboCAD, and SketchUp (free) are popular CAD packages in 2D.  SolidWorks, Inventor, and Blender (free) are popular CAD packages in 3D.  CAM software is what's used to convert your drawings into G-Code, which is the language of CNC.  You tell the CAM software things like the work area size, bit being used, etc and it takes your drawing and does all the calculations needed to create the vectors your machine will travel along.  Popular CAM software is MasterCAM, BOB, Dolphin, and Vectric's packages.  Control software basically takes the G code created by the CAM software and reads the file/moves the motors as instructed in the code.  You setup your motors and table limits here first, and then you can control things like speeds.  The standard in control software is Mach3 ($100), but EMC2 is gaining popularity and is free.


Additional costs add up as well for all the little things you need to get everything going.  Limit switches, wiring to the spindle, wiring to the motors, wiring to the switches, fixture clamps, spindle/router clamp, connectors, relays, switches, collets, BITS.  The bits really add up, but I'm sure you have a bunch of nice ones already.