You need three plates say 12mm wide by as long as you think necessary, all three are drilled with two holes, one at each end to clear a threaded spacer, fixed top and bottom by two nuts. The top plate has a screw thread in the center, through which you fit a screw to apply pressure to the sliding middle plate. Place tube between the bottom plate and the sliding one and squeeze.
How about that for a start for use on air?
Edited By KWIL on 28/08/2010 19:33:46