HDD Platter Removal

We want to be able to dismantle HDD's and destroy the platters to
ensure the data is destroyed. This seems to require a special tool to
remove the platters from the spindle on some of the older drives. The
spindle appears to be held on with some sort of odd plate type thing
with 6 slots on the edges. Is there a tool somewhere to remove this?
Any recommendations on getting them off? Thanks.