I scratch built a (CNC) milling machine. In steel.
2000 kg, 1300x1300x400 mm capacity, bridge mill, bolted welded assemblies, ballscrews, 3+phase VHF, with BP M head as spindle.
Took 13.000 hours.
And a 12x industrial lathe, with 1 micron res on x and z.
Servos, 10.000 counts-turn at 1:3 with HTD belts, secondary drive on spindle (servo indexed spindle as secondary drive).
I now work selling HAAS machines as sales manager for Spain.