Retaining Ring, M20 External 

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

Item No	Models
33	Harbor Freight 47158 Central Machinery Micro Mill Clarke CMD10 Metalworker Micro Mill Various X1-US SIEG Micro Mill
97	BusyBee CX611 Craftex Small Mill Grizzly G0619 Grizzly Small Mill Various SX3 SIEG Small Mill Travers Tools OT2225SX3 OTMT Small Mill
A018	LittleMachineShop.com 6700 HiTorque Large Bench Mill LittleMachineShop.com 6750 HiTorque Large Bench Mill Various SX3.5-US SIEG Large Bench Mill
A23	LittleMachineShop.com 5500 HiTorque Bench Mill Various SX2.7-US SIEG Bench Mill LittleMachineShop.com 5520 HiTorque Bench Mill LittleMachineShop.com 6500 HiTorque Bench Mill LittleMachineShop.com 5550 HiTorque Bench Mill Various SX2.7L-US SIEG Bench Mill LittleMachineShop.com 6550 HiTorque Bench Mill

Click your model to see the complete parts list.