Antler is a trick to drill for a fact. Couple of hints. If you spin a curved piece between centers, and look down at it, you can see a shadow or ghost of the solid hourglass shaped center that represents the largest hole you will be able to drill through that piece WITH THOSE CENTERPOINTS. Move the ends around to maximize the size of this section, and if you don't think it is big enough to drill through, try boiling the section for about 5 minutes and then clamp it in something to straighten it enough to get the bit through, and leave it to dry, then drill.
Even after it is turned round (or close thereto) between centers, a 7mm drill bit will still tend to wander when it tries to go from the soft marrow and into the harder wall of the antler. One way to minimize this is to drill to the center from one end and then swap ends and go through all the way.
