Drive systems
The motors are connected to one of three different drive systems to drive the machine’s axes:

• Ball screw: Large screw drives with ball bearings that run around the gantry.
• Lead screw: Similar to a ball screw drive but without ball bearings.
• Rack and pinion: Straight gear drives.

The drive system will affect the cut quality and accuracy. For detailed cuts that need to fit together perfectly or for fine engraving, ball screw drives are the best. They can cut perfectly round circles without leaving flat sections on curves. However, they are more expensive. Lead screw and rack and pinion drives are much less expensive, but may provide a lower cut quality because of backlash when the motor changes direction. Usually due to loose or poor mechanisms, backlash will negatively impact the quality of your cuts: circles may be imperfect or inlays may not fit.

Thru-vacuum system
A thru-vacuum system uses suction to hold down the material you’re machining so you don’t have to hold it in place by hand. It also leaves your hands free to feed the next sheet of material into the machine.

Spindles
CNC routers can have either manual single-cutter spindles or automatic tool changing capabilities. This means you can either perform a cut, stop the process, and change the bit by hand, or use a spindle that actually picks up a bit, makes a cut, and switches to a new bit.

Router bits
CNC router bits are sold in groups with different sized cutters to handle various materials. They must be kept sharp at all times to ensure accuracy.

You typically get a set of basic CNC router bits when you buy a router, but you’ll probably want to augment those by buying your own bits out of a catalogue or through a web site. Standard router bits with carbide tipping are relatively inexpensive ($20-$40 per bit) but they quickly become dull with use.

You may want diamond-tipped or diamond-abrasive bits, instead – they’re much more expensive, but they last longer and will rarely need to be replaced. They can also be serviced four to eight times before they need to be replaced.