IBM EGX-400 - Manual (Page 55)

51 Chapter 3 - Preparations
Lock nut
Lock nut : Tighten
[AUTO Z CONTROL] : OFF
[REVOLUTION] : ON
Collet for end mills (optional)
End mill
3-5. Cutter Installation Method 4 (End Mill)
This is for when you perform three-dimensional cutting of reliefs and the like using an end mill. An optionally available
collet set for end mills is required to install an end mill.