I have begun doing casting pen blanks of various materials that have proven to be difficult to trim or turn. I collected a bunch of cool sea shells from the beach and cast them into a nice pen blank only to have it get ripped up when doing some of the processing for getting the blank to length with a typical end cutting tool.
My solution (not totally original) was to sand the blanks instead of cutting them. Worked nicely. Then I tried to trim the blanks to length with my disk sander. Sorta worked. If you have ever trimmed a pen blank, it is essential that the ends of the blank be dead perpendicular to the center line of the pen, and be consistently flat across the entire surface. Hard to do on a drum sander without some help.
I read a great article on the International Association of Pen Turners (IAP) on using your lathe with a holding jig to cleanly sand the pen blank ends on your lathe. It used a 3/4" piece of MDF attached to a threaded collar which you then threaded onto the headstock. One of the IAP members created and sells a holding jig for the tailstock, allowing me hold the blank perfectly perpendicular to the sanding disk. Using a sticky sanding disk on the mdf plate and turning the lathe speed to medium slow, putting the pen blank into the jig has allowed me to get dead on perfect ends!
Here is my setup in pics. Feel free to ask questions if you need more -
Wood plate without paper attached to headstock
flange plate attached to center of MDF which was attached to a larger block of MDF then turned to round
Tailstock mounted holding jig, with punch pin attached holding the pen blank for end finishing. The jig is made by Rick Harell, a member on the IAP site. The metal jig cost about $40 with the #2 Morse taper attachment. The pins are from PSI - their pen disassembly kits (also available at Harbor Freight). Sanding disks are about $1 each.
This setup gives me really great control over the end sanding of the blanks, and has eliminated the tear out sometimes caused by by end milling jig.
Enjoy!
Kevin