Ive had tubes pull out on accident because I had a little epoxy inside the tube and gotten them stuck on the mandrel. I heated the mandrel on both sides of the mandrel with a lighter and kept pulling on the blank. heating and pulling, heating and pulling, over and over until the blank came off the tube instead of the mandrel,. They were 7mm tubes and close to the mandrel. I dont know what size tube you have so how you heat it is up to you. Good Luck!