YOu can find the long shank drill bits from specialty stores, or Woodcrafters, Brownell's, and other suppliers. You probably want something like a brad point bit for this kind of work. Antler is notorious for having soft and hard spots, that can turn a drill bit. ALWAYS use a pilot hole First.
As to size of the hole, measure the stems of some of your other pipes you like, and draw well. The outside diameter of the part of the stem that enters the NECK of the bowl varies.
I just measured two of my pipes, and one measures .270, and the other measures .302" ! A quarter inch diameter drill bit is obviously close. Then reamers are typically used to smooth the hole and enlarge it a bit. How much depends on the reamer used, and the craftsman. The diameter of the main bowl also varied. One is .730. The other .837". If you are going to make a pipe to smoke, then make it comfortable to do so. Don't make the bowl so small or narrow that you can't get your finger down in it, easily. I have smoked pipes with shallow bowls, and deep bowls. I have had wide bowls, and narrow ones. I didn't like the narrow deep bowls because they became too hot. I didn't like the wide shallow bowls, because too much tobacco burned too fast, and the bowl got hot, but the tobacco didn't last very well. The pipe was okay for a short smoking break, but gave me no other option. I can pack a pipe with only half a bowl of tobacco for a short smoke, if that is my time constraint. Then, when I have more time, the same pipe can be packed with more tobacco, for a longer, more leisurely smoke. My best pipe now is a Danish Briar, made by Knute, I bought back in the late Fall of 1972, right after I finished law school and passed the bar exam. I used some of the money I was sent by relatives to buy myself an early Christmas present. I still have the pipe, and its still one of the coolest smoking pipes I have ever smoked. But, its a heavy pipe, with a deep bowl, so I don't carry it around to smoke on the street. It stays at home, well protected, and is used for a nice long, slow smoke once in awhile.
Don't expect that antler pipe to smoke cool. It can't. So, consider a more shallow depth for the bowl, and use as thick a piece of antler so you have plenty of antler around the bowl to absorb the heat. especially on the bottom of the bowl. :thumbsup:
