Can’t get drain assembly out of sink.

[Peelwizard]

Hi, I cannot get the sink assembly out of the sink. There is no nut underneath, it seems the top and bottom of the assembly screw together. It has been in there about 15years I reckon. Any help on how to unscrew it?
There looks to be 4 small recesses inside that you could a tool into and try and unscrew from below, but I don’t have anything to hold it in place.

 

[Deleted member 120897]

It looks like a pop up waste, so the base (the part under the basin) will unscrew counter clockwise.

 

[ShaunCorbs]

Two chisels crossed normally does it for me

 

[Ben-gee]

Make sure you use your “removing excess plaster/brick” third tier chisels; and not your “fine cabinetry hinges” chisels!