BISECT AN OBJECT
The steps listed below will guide you to bisect an object into two pieces.
1. Add an object in Object mode. Now switch to edit mode and select all the vertices of the object.
2. If tool shelf is not visible in the 3D window, press "T" key to make it visible on the left side of your 3D window.
3. In the tool shelf, click on Tools > Mesh>Add>Bisect.
4. Place the cursor near the object and draw a line across the object so as to cut across it.Press Enter key to confirm.
5. In the tool shelf, look below, under the panel named "Bisect" you will find three check boxes, Fill, Clear Inner, Clear outer. Selecting clear inner will delete the lower half of the object, selecting Clear outer, will delete the upper half of the object. Selecting the Fill check box will cover the cut edge with a face.
7. Go to object mode, Object>Transform>Origin to Geometry.
8. Deselect both objects, select the upper portion and pull it away.
