Trouble taking head off tripod legs
 

I have been trying to take a Manfrotto 200 head off my 117 tripod legs. The three locking screws have been taken out completely, and the whole joint has been sprayed with WD40, but it will not unscrew. I have tried tapping the head plate with a screwdriver and hammer, but all this does is make indentations on the plate. Please can anyone help?