PCB Milling

Sainsmart 20k RPM Spindle
Spindle start code 
 M03 S5000.0
G4 P.25 
M03 S10000.0
G4 P.25 
M03 S15000.0
G4 P.25 
M03 S20000.0

PCB Milling In FlatCAM
If cutting the back (underside) of a board, as would be the case for most single sides PCB's, the gerber MUST be flipped in FlatCAM.