#*$*#@@# Brake lines keep slipping out of my flaring clamp!

[yody]

So i am trying to do some double flares on regular brake lines. I cut the brake line smooth it flat and then chamfer the outside and inside, I then put it in the clamp and use the black piece to guage the height, then i put the black piece with the nipple going into the inside of the line. THen i put the assembly in a vice and tighten the hell out of it, then i put the flaring tool onto the clamp and tighten the living day lights out of it. then i proceed to do the first step of flaring, but the damn brake line keeps slipping out of the clamp!! I have a ridgid 345 tool which some people like. I have super tighten both my work vise and the flaring clamp and it still slips out. what is going on here??