Do you mean for pulling out your blades and attacking? That time delay?
If that's of interest for anyone, I tried to take a look at it myself by recording my character hitting a standing still target switching between normal attack chains and chains forcing redraw (all gapless), then watching it frame by frame. As far as I can tell for Dual Blades the delay with redraw seems to be about 0.55s.
Does anyone know the exact redraw times/delays for different powersets? I'm specifically looking for Dual Blades, but interested in everything else as well.