Folder Permissions

I run a studio with five G5's (all running 10.4.2) networked to a G4 (10.2) runnning sharepoints for network volume mounts

My problem is that whenever a user creates a new folder on the server it is automatically assigned the priveledges of r/w to that user and then only read rights for anyone else.

How can I set this so that when any user creates a new folder everyone can r/w to it - at the moment we have to manually do a "Get Info" and change the permissions.

I have tried TinkerTool 3.4 - but it doesn't seem to work.