How do I remove a bathtub drain

Is the space below the tub open or is there a finished ceiling? Is the a removable inspection door on the otyher side of the wall from the tub? Tell us why you need to remove the drain to give us a better perspective.

Dry wall around the tub has been removed. The tub is being replaced by a shower. The drain needs to be removed and replaced by a new one, centred in the middle of the shower.

Can you reach underneath? If the inside of your drain has a cross bars within it, you could use a plumbers tool that looks like a two pronged fork with a handle and try to turn it (I use the handle of my old pliers to do it at times). You can use another wrench on those handles if you need more leverage.

A dumbbell wrench like this one may be a bit more universal for your situation. Superior Tool at Lowe's: Tub Drain Removal Dumbell Wrench (http://www.lowes.com/lowes/lkn?action=productDetail&productId=19173-943-06020&lpage=none&cm_mmc=search_gps-_-gps-_-gps-_-Superior%20Tool%20Tub%20Drain%20Removal%20Dumbell% 20Wrench) You have not answered my questions about access from below or behind. Is the tub cast, acrylic or what. Swanstone makes a shower pan made for fitting into an old tub design so you do not have to move the drain, interested?

And here's what everyone's talking about;
A iub tool to fit the cross bars of a tub drain.
A Swanstone shower pan to replace a tub and a drain assembly to help you out. Do you need more directions? Good luck, Tom