Screw, Spindle Sleeve Guide 

In your instruction manual, this part appears on the parts list as:

Item No	Models
55	Harbor Freight 47158 Central Machinery Micro Mill Clarke CMD10 Metalworker Micro Mill Various X1-US SIEG Micro Mill
60	LittleMachineShop.com 4660 HiTorque Micro Mill LittleMachineShop.com 4700 HiTorque Micro Mill
85	Harbor Freight 47158 Central Machinery Micro Mill Clarke CMD10 Metalworker Micro Mill Various X1-US SIEG Micro Mill

Click your model to see the complete parts list.