Hi I have just purchased a Festool DF 500 Domino tool, I also have a CT15 dust collector, And it need some sort of connection piece, Can any advise me what to buy please.
Sometimes the hose end can be really stiff and hard, just push it on really hard while rotating slightly, but do this without twisting it side to side so you don't split the end of the hose connector.
CT hoses are designed for a tight fit with the Festool machines so the hose won't get disconnected accidentally when the hose is pulled or drags along the edge of the workbench, etc. Try angling the hose end slightly when you push it into the Joiner's port. These videos may help:
Start the clip at 0:42 -=42s
I've seen some third-party 3D printed connectors that aim to change the angle of connection away from the body of the machine. I have no idea how tight those connectors are with the CT hoses. By the way, welcome to the Domino Joiner Club.