Ok, this is a late response to the question, but better late than never. Being is South Texas and deer roaming free all over the place, I get lots of materials free for the picking up. Free is always good in my book. While I spin all kinds of woods and other materials, my customers overwhelming purchase antler pens.
First the question of 'freshness'. Natural sheds are always better than any other antler development stage. By then the velvet is gone, and the antler has 'calcified' fairly well. Depending on the breed of the deer will also determine whether the antler is solid from base to tip. Antler is very solid and hard at the tips, but this usually diminishes the closer to the base of the antler. Some breeds have a hollow vein that runs thru the core branch. Not usually a problem since you are drilling it out any way.
I used to just store all the racks in the shop until I was ready to use them, but now I go ahead and band saw all the branches off the trunk and store them in big trays in my shop. Easier to manage that way. This has the added advantage in that I can determine how much color is in the antler from looking at the cross-section. Not all antler is bone white. Diet and environment plays a big part. I have had grey-blue, green, pink, ivory, purples, and other shades. Pretty cool.
I usually discourage customers from ordering a pen with upper and lower barrels of antler. Any sealant with eventually wear thin, and antler is porous, and any oils from the skins will be absorbed and discolor the pen. I have seen pens very yellow and grungy after only a year or two, while pens I made 6-7 years ago still look factory fresh.
So, when I am ready to make a pen, I pick a piece of antler that is of appropriate thickness and not too curved. Curved is ok, as long as I can drill from one end of the blank to the other without penetrating the external bark. This to have to do by eye. Take your tube and line it up against the antler and locate it where the curve and thickness are suitable. I then mark off the end of the tubes on the antler with a pencil. Try to get the marks across the antler at a 90 degree line from the tube. I then use a band saw to cut my blank. I ALWAYS cut it long. You can always trim it down to the final length, but adding a filler is problematic. Excess antler goes back into the storage tray. Short pieces are saved as well to be used as fillers or center rings or such.
I guess I should also mention that you should wear a good quality air filter/mask. Antler is a nasty material to begin with and breathing in air-borne particles is just asking for health problems.
To help with drilling, take your pencil and lightly mark a vertical line down the entire blank. If the blank is fairly straight, you can skip the next step. Go around the blank and mark a vertical line for each quarter segment of the blank. Some people I know use the blank holding jig that holds onto one end of the blank is a vise-like arrangement. This works for straight blanks, but curved blanks is prone to problems. I created a jig from a 4x4 block that has a 45-degree nock cut into it. The block is about 5" tall, so most pen blanks will fit without slipping over the top. This block is screwed to a base mounted on my drill press. The antler blank is placed into the jig with the curved side out (away from the jig). The pencil lines now help you visually determine if your blank is vertically centered in the jig. You may have to shim you blank to get it vertical. Once you do this, I pressure clamp it into place and drill it out.
Take your time drilling. Stop and back out your bit frequently. If the antler is old and completely dried out, you'll get lots of fine dust everywhere (remember the mask warning?). If not, then the antler tends to be moist internally and this will stick to your drill and keep gumming it up. When I finish drilling, I keep up my bits before any antler material can dry out on the bit. Absolute pain to remove later on.
Now dry fit your tube. I hate it when I butter up a a tube and it jams in the blank before sliding all the way in. So dry fit your tube. If it doesn't slide thru, I use a round rasp to smooth out the bore. Once it fits, glue the tube in. I use CA, but other use epoxy.
Once your glue is cured, square up your blank. One end of the tube should be fairly flush already. I start there. The other end should be long (you cut your blank long, remember?). Depending on how much excess needs to be trimmed, I may go to the bandsaw again and trim off the excess, then square up the blank.
Now, before starting to turn, check your blanks core near the tubes. If it appears porous, drip some thin CA into the porous sections and let it wick into the blank. Do one or two drops at a time and let it wick in as much as it will take. If the blank is solid, skip this step. Let the CA cure and harden before starting to turn. You may have to square up your blank to remove any excess CA that has expanded during curing.
Mount and blanks and spin. Remember to wear your mask. My spinning speed varys based on the hardness of the antler. The harder the blank, the faster I spin it. Use sharp tools. Take your time. You may to stop a couple of times and 'freshen' your tool edge. You also will get an acculumation of antler dust on the top side of your cutting tools edge. You'll need to clean it off the same as you did your drill bits.
If your blank is solid and hard all the way thru, then life is good and easy. If you encounter some porous areas, you'll need to stop and drip some thin CA into the area and let it wick up as much as it will hold. After wicking, I shoot it with some accelerator to quick dry it. Otherwise, when you start spinning again, you'll get CA glue throwed all over the place. Turn the blank down where you need it. If you do it the way I do it, you should still have some bark exposed and have a pen with some extra character.
Finish the blank as you normally would. I tend to use a friction polish or other material to seal the antler to prevent the antler from absorbing anything extranous and unwanted.
Anymore questions? Email and I'll give you some more guidance.
Travis