Below is a picyure of my own DIY CNC wood router. It's a gantry machine with a finished cut area of 15" x 36". Construction is basically all wood except for the precision components. On the long axis (gantry) it uses two 1.25 inch precision shafts with two dual pillow bearing blocks, powered by a 282ozin bipolar motor. Rotary to linear conversion is done by a Roton 1/2" .2" pitch ACME screw and antibacklash nut. Rapids can run over 200 IPM, but I restrict it to 180 IPM to minimize wear and tear on the machine. The 15" travel axis is two .75 inch precision shafts with four pillow block bearings. The 15" travel axis motor is 200 ozin running unipolar. Rapids run around 200 IPM, but for normal use are limited them to 160 IPM. The rotary to linear conversion is again a Roton 1/2" .2 inch pitch AMCE screws, this axis is using a normal Roton nut. I took the easy way out on the Z axis, with a long version of the Instant Z by Paul Jones at CNConabudget.com. The Z axis motor is 120 ozin unipolar. I run up to 100 ipm cutting feed rate on many woods. The Z and 15" travel axis are driven by my Halo Board http://pminmo.com/PMinMOwiki/index.php5?title=Halo with a 34V DC 10A power supply via my DCS1 http://pminmo.com/PMinMOwiki/index.php5?title=DCS1 pcb and a MPJA 24V 10A transformer as outlined in my article on building a Simple DC power supply. http://pminmo.com/simple-power-supply. The long axis is my test bed for bipolar drivers...:-).
I'm a firm believer in getting the most performance for the least dollars spent. Many people start by routinely trying to skimp on bearings and shafs and wind up having to buy bigger mtors and more expensive electronics to get reasonable performance. When they do that, they still are limited in precision by the innaccuracy of gas pipe and skate bearings or equivalent. By spending some time on EBAY and searching the web, used precision linear shafts and bearings can be found at really reasonable prices. For example the 24" .75 in shafts and four pillow blocks I purchased for less than $100, the two 1.25" 42" shafts were less than $40 and the two 1.25 inch pillow blocks less than $100 for the pair. One point I would make, is that when you buy bearings and shafts seperate you save money. It takes some patience and shopping, but the savings over buying a "complete" set of shafts and bearings is considerable.