Spindle, 3MT, SX3 Small Mill 

Chris' Tips
Here is a drawing of the spindle.

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

Item No	Models
2	BusyBee CX611 Craftex Small Mill Grizzly G0619 Grizzly Small Mill Various SX3 SIEG Small Mill Travers Tools OT2225SX3 OTMT Small Mill

Click your model to see the complete parts list.