Beautiful Buckeye Burl Blanks Ken,
Regarding the Tight Fitting Hardware, are you cleaning out the Tubes after they have hardened in the Blanks, and you have squared off the Blank Length?
I use a Countersink Burr to remove any possible burrs, from the brass tubes, then I use a small Rat Tail File, to clean the ends where the hardware is to fit, of any adhesive or muck that may have got into the Tube.
I notice that the transition to the Hardware diameter is very sharp. It is a common problem with new turners not being confident or experienced to be comfortable taking the Blank, down to the hardware size.
It could be a good suggestion for you to turn down some firewood to the bush diameters to gain the Experience and Confidence, rather than use Expensive Exotic Blanks.
There are some excellent YouTube video's you might like to look at.
I look forward to seeing some of your future Pens.
Regards,
Brian.