A pcb engraver under 150 dollars.

[Corporate666]

I'll check runout again. Before I could only measure down to .25mil.  I have better measurement options so I can certainly check again.  All I can say for sure is my runout last time I checked was below what I could measure. 
I have been using what I have because I haven't found a source for a better option.  And I refuse to buy from USA companies that charge double advertised price to cross the boarder.  To be honest I stopped looking after 4 months of such dead ends. 

If you have a recommendation for a .18mm end mill I will try and get one.  If I have success I will get .25mm and .5mm end mills also, when I use up what I have.
 
I think machines changes will be effected with a new mill when the time comes. 

I use Eagle and metric.  I can only get imperial exports so there is a double conversion.  Therefore I call the .25mm a 2.4mm, so it won't choke on .25mm isolation paths.  It was the easiest fix because I use a .1mm grid.

eKretz is right about runout... if you are out even by 0.1mm, you could be quadrupling the recommended chip per tooth feedrate when the "high side" of the mill gets buried in the material.  400% of max feed will kill a small bit instantly.

It's important to measure runout as you cut... you can do it on the smooth portion of a cutter extended out of the holder a little...but to check runout where you cut, get a gauge pin in the same diameter (or close) as your cutter and use a 0.0001 dial indicator on the table and slowly rotate the spindle.  You should be able to eyeball to within 1/4 of a graduation which would be 0.000025 inch, or 0.0006mm.  The higher quality the dial indicator, the better... but even something like this will give good results:

http://www.ebay.com/itm/PRO-QUALITY-030-DIAL-TEST-INDICATOR-0005-GRADUATION-/121008094933?pt=LH_DefaultDomain_0&hash=item1c2ca4fed5

Don't underestimate the effect of crap toolholding.  I've got some ER collets on the mill that are wonderfully accurate, and some that are total crap.  I only buy Hardinge brand collets now when I can or Kennametal, because even other supposed premium brands like Lyndex have often been total crap.  Many people cut corners on tooling, buying Chinese collets and such.  Check the runout back to back with a quality part and you will be shocked at the difference. 

[negativ3]

The option I went for as a PCB milling machine. It does involve a fair bit of DIY to get it all setup/working, but it's worth it. Less than $1500 all-in.

A few links to share...

HARDWARE

3-axis Base Machine, Microcarve MV3:
http://www.microcarve.com/mcMV1.html

Stepper control, Gecko G540:
http://www.geckodrive.com/geckodrive-step-motor-drives/g540.html

Spindle, Kress 1050 FME-1:
http://www.damencnc.com/en/tools/kress/kress-milling-motor/87

Spindle Control, SuperPID:
http://www.vhipe.com/product-private/SuperPID-Home.htm

Limit Switches, Homebrew with Honeywell Hall Effect sensors.
http://www.ebay.com/itm/321052908870


PCB Cad software

CADSOFT EAGLE:
http://www.cadsoftusa.com/

PCB-GCode ULP for Cadsoft Eagle:
http://pcbgcode.org/index.php

PCB-GCODE Wizard:
http://www.pcbgcode.com/


CNC Control

MACH 3:
http://www.machsupport.com/

Example PCB...