To explain WHY I picked the "R" Bit:
I measure the OD at .335" (it is my habit to measure every tube before I start a pen, so this was what my first few were)
The 11/32 hole seemed sloppy to me (.3438)
"R" was available at .3390
I use almost all resin blanks, which do not shrink after drilling. Also, I don't feel a need to expect high heat on the pen, so the brass tube should not expand.
IF I were making pens for shows, I would make the hole larger, so there is room for brass expansion and for painting the hole. But, I usually use black chrome, chrome or white tubes, these days---no real need to paint.
So, take your choice, based on how you expect your pens to be treated and what concerns you have about the brass tube expanding. The "R" is a SNUG fit---which may NOT be optimum for a wood that you think MAY shrink, while the tube expands!!
CRACK!!!
FWIW,
Ed