I don't use either and haven't had any related failures that I know about. I don't see a need for a solvent after roughing with sandpaper. Just my 2 cents and relatively small sample size ( couple hundred pens).
Be careful with acetone or alcohol although they are good degreasers they can cause a tube to sweat. Napatha will leave an oily film. I have found gray scotch-Brite does a good job. It not removes oily finger prints, but roughens the brass slightly for a good grip.
The point is to assure the strongest possible bond between the tube and the wood/plastic blank.
Wiping with acetone (or some other solvent) is intended to remove any grease left on the tube from its manufacturing process.
Many folks scuff the tube with an abrasive to provide a mildly rough surface for the glue to adhere better. The thinking is that the glue may not form a good chemical bond with the metal tube, but it will cure in the gap between the wood and the tube, and if the tube has been scratched, the glue will cure in those scratches to lock the tube into the blank mechanically.
Thanks for the information. It is very useful. I do scuff the tubes and have been careful about making sure the tube is covered in epoxy. I also twist the tube in one end, then remove it and insert it in the other end while twisting hopefully to smear the epoxy well so the entire inside is covered. Anything else I should be doing?
I've not done pens in a long time but last Christmas I gave our pastor a pen and this year her husband ordered seven to give to his management team. The gift that keeps on giving.
I do scuff the tubes...usually between centers on the lathe and then file off any sharp edges on the ends of the tubes. Brass tubes make great scrapers .....as you will find out when you insert them into blanks which were painted inside. That is why I soften the sharp ends.
Back to the question...I will wipe the tubes prior to gluing with denatured alcohol. Even though the scuffing probably removed any manufacturing oils, I also want to clean the dust from sanding as well as my fingerprint oils.
Yes, 5 minute epoxy and I use a toothpick to spread some epoxy in each end of the blank as well as applying to the tube and most times I too insert from one end and then insert the tube from the other end for good glue coverage