Summit Tunnel Air Drills in 1867

From: kylewyatt@aol.com

Evidence that the Central Pacific did at least try power drills in Summit Tunnel. I wonder what patents the drills were built under.

—Kyle

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Summit Tunnel – Air Drills in 1867

April 1, 1867 – San Francisco Alta Californian – from GM Best notes

Central Pacific – Summit Tunnel

Vulcan Iron works built "atmospheric drilling machines", four of which were used by the Central Pacific in Summit Tunnel.

Drilled 1 1/2" holes for nitro-glycerin.

Drilled at rate of 1 1/2" per minute.

Air supplied by air pump – steam powered - on surface.

Air pressure 20 lbs.