This wont help you stem drillers, but is an interesting story and approach.
Having had access to an X-ray machine when I worked in an Indian Reservation medical clinic years ago, I drilled a 1 1/4 x 18 pipestem blank out of red pipestone I traded for near Pipestone MN. I simply clamped the blank gently in a vise horizontally, and used a long 1/8 drill bit in a hand held electric drill to eyeball the holes from each end. About every 2, I took the blank over to the clinic and X-rayed it, correcting my course as I went. The holes met at the middle of the blank with only a 1/16 offset, which I worked carefully to ream smooth. It became a beautiful pipe, has been blessed by a Medicine Man, and used in two Arapahoe Sun Dances and numerous medicine sweats and private ceremonies. However, the pipestone is easier to drill straight than hardwood, and would never hold up as a tomahawk handle!
Bill Paton, M.D.