Hi Joe;

The 2 CNC mills have cost between 500 and $700 to build depending on the 
availability to free materials and parts.    About $1000 if I purchased 
100%.    Linear bearing purchased on Ebay.

Backlash-Mill #1 used 1/2-20 threaded rod and machine tapped brass nut, 
backlash a couple of thou.   Mill 2 uses Rockford ballscrews.

Spindle-both mills have hardened and ground A-2 spindles that I made.  Mill 
1, 1/2 dia spindle, milll2, 1" dia.  Both use a 1/8 hp Dayton 90 V DC motor. 
   Also variable speed.   I find these in the dumpster at work. Replace the 
brushes and clean them up, good enough for me.    The 550 oz/in steppers 
came from work as well.

Mill #1 was never designed to be rigid mostly a learning project.   No way 
is that head rigid.   Hangs out 10" beyond the  linear slide.   However, it 
is smooth.   Machines wood and splastic well.  Great for engraving any 
material.     In time I'll convert the head to the mill #2 style.

Mill #2;  Has a 6" sqr steel tubing for a column.   1/2" steel plates welded 
top and bottom for mounting flanges.  The ram is 4" steel tubing with 3/8 x 
4 CRS welded as mounting flange.   The ram is clamped to the column and has 
12" of adjustment kinda like a Bridgeport.   I can engrave a sign 24 x 24.   
Mill #2 machines aluminum well.   Not sure about steel.   The "Z" axis uses 
square gibs instead of rods and bearings.    Defection will only take place 
in the ram and that is not likely.

Got to run,
Jim