For silver to be safely used requires a close fit, for enough surface area, to attain the needed strength level. Not what a butt joint offers unless a sleeve/plug is used, which is a common method and one that I've done quite a few times in varying tube diameters (although not yet a steerer). How deep into the steerer your stem needs to be and where is the steerer's upper edge of the butt transition are two more factors I would want to know. I have recycled a couple of fork crowns in my past and would consider replacing the entire steerer first. Andy