The ten drills in this picture have obviously been

worn down from excessive use. Two or three of them

may have had one end snapped off during the drilling

process. The drills in this picture range in size from

1/2 inch (1.2cm) to 15/16 inch (2.3cm) long.
   According to Morse (1983) Michael Sierzchula's drilling

experiments in 1980 showed that with the use of a bow

drill he could effectively drill one shell bead in 10 minutes.

He reports that after 12 holes the two microlithic drills were

still functional. He was able to drill a fresh dog canine tooth

in less than two minutes.