I just ditched my printed bowden clamp for a blind rivet nut.They are less bulky than standard nuts, and they also feature a very convenient shoulder, to be embedded in printed parts.The result is incredibly solid.Sanding the tube makes its easier to grip and let the thread dig their way better at the beginning.Insert a nail or rod with the appropriate diameter to clamp the tube with pliers so as not to pinch it.Then screw the nut on the tube.Check here for further explanations: http://betterprinter.blogspot.fr/2012/10/robust-bowden-attachment-with-blind.htmlOne final note: you can use them also in your printed parts themselves when you want very solid and clean threads.