I picked up a Craftsman lathe w/ tools and a pen mandrel shipped to the house... I ordered some pens kits and got ready to turn , and after glueing the tubes in the wood, they would not fit on the mandrel. I then checked some new tubes with nothing attached, and they would not fit either. So, either the tubes are too small, or the mandrel is set up for 8mm tubes.
Can anyone measure the mandrel for the 7mm and 8mm tubes and let me know what the measurements are? I may have to do some more shopping.