Vacuum chucking is becoming more common. From home built systems to more expensive commercial systems, they all have some common issues. One of those is getting a good seal between the chuck and the bowl.
The editor of the Segmented Woodturners newsletter recently tested out a new rubber chuck gasket specifically made for the OneWay™ Vacuum Drum Chuck and the Hold Fast™ Drum Chuck. He reports that the OneWay™ version fits his chuck perfectly, is robust and that he has seen good results. This is a reusable seal that does not require any adhesive. You can check them out at rubberchucky.com