How to remove kitchen sink basket with no locknut?

[rsobers]

I have a kitchen sink basket that's leaky and has a bunch of gunk caught under it. I want to replace it. All the instructions I see for removing and replacing a kitchen sink basket start by removing the lock nut underneath.

My sink, however, doesn't have a lock nut. The pressure cup is plastic and I have no idea how to remove it.

This is what the basket looks like:

http://i.stack.imgur.com/Jti91.jpg

Here's what it looks like from the top.

http://i.stack.imgur.com/mNYFi.jpg

I tried holding that little center piece steady with a screw driver and tried to unscrew the basket from beneath, but it just turns and turns and won't loosen. Any ideas?

Thanks!

 

[Mr_David]

the bottom and top piece are held together with the screw you can see looking down from the top

 

[Matt30]

I always find a flat head screw driver is a pain to get in there so I use a coin (usually a toonie...yes...our $2 coin is a toonie).