Abstract: The CNC Lathe machines are constructed base on conventional lathe machine. This paper is the conventional lathe can be modified to CNC lathe machine. For 2.5 m length conventional lathe machine to be CNC lathe machine, reassembling is done. With the disloged parts of conventional lathe, some changes, substitutions and necessary parts construction is done to be CNC. For converting to CNC, some necessary parts for changes and substitutions fagor materials are used. Gear box design of the spindle unit in CNC lathe machine and design calculation of Gears and Shafts in Head Stock are expressed. This study is including Gear Train, Gear Design, Strength Check, Dynamic Check and Shaft design material.