It CAN be done, but that doesn't mean it SHOULD be done. They do make covers that can go right over the present drain cover, and then you can tile right over its flange, and that's what holds it down. You first need to make sure there's no foreign material on the tile-- no soap scum, no body oils, no nothing. Then hit it with a sander to rough up the face of the tile, and use an unmodified thinset mixed with a liquid latex additive.

This does not sound like a do it yourself job. Maybe I should just bite the bullet and have someone bust it up-since the old cast iron tub will have to be busted up to replace with a shower. I know how I felt when I tried to remove the wallpaper and found the walls ill prepared-then discovered that there were at least 2 different layers of wallpaper under the one I was trying to remove. Boy was I hot!!!. Wallpaper had to become part of my wall and get painted. That is probably how someone would feel about tile over tile.

Johnny _holbert - This is a 11 year old thread. I see you are going through many old threads placing links within your comments. Is this a new HOUZZ version of SPAM? Current technology provides products specifically designed to promote bonding for this exact scenario. A flooring professional would be aware of this. Structural integrity would be a concern. The following links address this threads topic. https://www.mapei.com/us/en-us/products-and-solutions/products/detail/eco-prim-grip https://laticrete.com/en/tile-and-stone-installation/adhesives-and-mortars/multipurpose-bonding-primer/prime-n-bond

if it were mine tear it all out. the tile is only as good as the foundation its put on. the cracks will telegraph through the grout joints and tiles. putting tiles on sealer that is no good would be faulty as well. if the sealer gives way so does the tile. 3 to 4 years down the road youll wish it was done right.