In the past, if the tapers are in good shape, I have taken a piece of chalk and made about half a dozen lines of chalk along the taper. Fit up the chuck twisting it on the arbor to spread out the chalk, then tap the chuck into place with a plastic hammer. It works like a charm getting a loose taper to hold. In fact, I've had trouble separating ones that I have used chalk on. Be careful not to get chunks of chalk on the taper, that can cause runout.
Richard
Richard