Tube Holder On A Machine

Hey, does anyone ever have trouble putting a tube through one of those tube holders on a machine? I'm talking about the round protrusion coming off the machine where you would normally thread a tube through. I've had two machines with these little protrusions and the only thing I can tell you is I have one hell of a time, almost forcing, if you will, the tube through this thing! If your still clueless of what I'm talking about, take a look at Seth Ciferri's micro liner. Yeah, THAT thing! It's a pain in the ass. Do any of you have any suggestions that would make like a little easier, such as a certain circumfrence for a tube to fit with ease? Thanks

Get 5/16(.312) reamer or jam a screwdriver in there and open it up.

DO NOT JAM A SCREWDRIVER IN IT AND OPEN IT UP!!!! Take the vice screw out. Put a spare rear spring in the slot, then thread the screw til it pushes on the spring, this will open the slot. You only need to do it a very little and it will make a huge difference. AND NEVER TIGHTEN THE VICE W/O A TUBE IN IT!!!