I want to clean up and zinc plate the casings on my bilstein struts so i need to remove the inserts from the casings, "Markk" one of the users on here said just undo the nut on the bottom of the casing and unscrew the insert but that doesn't seem to work... it just spins and spins even when pulling on it whilst turning as i assume the insert is just turning in the insert,

i also tried giving the screw that sticks out the bottom casing a tap with a hammer and some wood over it to protect it but only lightly as i didn't want to damage anything and that didn't work either

Any ideas please people?

Here's the struts


Also the screws that stick out the bottom are slotted and hex so is this for adjustment of rebound?

Thanks
Marc