There is a threaded 'cup' that screws down over the external thread on top of the spindle. Screw this down lightly (i.e. not even finger tight). When you then unscrew the drawbar using an 8 mm spanner on the square section on top, the drawbar pushes against the cup and thus ejects the tooling from from the taper at the lower end of the spindle.
Hope this helps
Martin
Note there is a very detailed manual for a very similar, but not identical machine (e.g. it uses R8 tooling rather than MT2) at cdn0.grizzly.com/manuals/g0704_m.pdf
Edited By Martin Whittle on 17/07/2014 22:31:55