IllustrationArtifact · Authenticated · London
Petrie core No.7 (7 G)
Petrie said a drill cut 1 inch into granite per 60 turns. Christopher Dunn says that is 500 times too fast.
A feed of 1 inch in 60 turns, in granite. What test would settle whether copper and sand can do it?
Illustration made for The Nommo, not a photograph.
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