Home › Blog › Buying Guide › Technical Evaluation Guide: How to Identify a Quality Used, Secondhand, Pre-Owned, Surplus Ingersoll Masterhead 4th/5th Nutating Spindle 25804 – 45 Unit Milling Head 1) Machine / Head Overview & Key Terminology Nutating spindle (also called “nutating head” or “Masterhead”) is a tilting / oscillating head designed to provide 4th / 5th axis motion (tilt / rotation) in heavy milling machines....