I just purchased my first ROS, it is a porter cable model 333. The problem I'm having is keeping the sanding disc on it's pad. It is a 5 inch, 5 hole hook and loop. Not sure why it is called that, should be call press and stick. Unless I'm doing something wrong, the adhesive backing on the back on the discs are not working very well. As soon as I lift the sander off of the work piece, the disc flys off. The only way I can keep it on is to turn it off while keeping the disc on the workpiece.
Greg, assuming that you're using the correct discs (Hook & loop aka Velcro), the hook part of the system sometimes gets clogged with sanding dust. Just use a brush or shop vac to clean off the pad before you attach the sandpaper. PSA discs will not work on H&L.
Sounds like you may be trying to use adhesive backed discs with your hook and loop sander. The sticky discs need a smooth surface to stick to - the hook and loop discs have a kind of fuzzy surface that attaches to the 'hooks' on the sander pad.
Congrats on your purchase. It does sound like you got the wrong sandpaper. Five hole hook and loop means velcro with five holes through the paper for dust collection, no peel and stick.
Greg, I think the previous posters were on the right scent. If you have sanding discs with a fuzzy back then the pad on the sander has to have the rough hooks. If this is what you currently have then something must be defective about your hooks because the velcro-hook system holds great. I've had pads fly off with the adhesive backed system but never with the velcro-hook. Boyd