Listen for high-pitched whines or grinding. Check for "runout" (wobble) using a dial indicator.

Check if the seller is including tool holders (BT40, CAT40, etc.). Buying these new can cost thousands. 🏁 Pro Tips for the Hunt

This is the "play" in the lead screws. Excessive backlash means the machine can’t hold tight tolerances. 💻 Don't Ignore the Controller