Method of making bore holes
United States Patent 1898926

Inventors:
Godefridus, Aarts Christianus J.
Alphonsus, Mekel Johannes Anton
Publication Date:
02/21/1933
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Assignee:
Walter, Franciscus Cornelis Baa
Primary Class:
175/16
Other Classes:
175/309, 266/129, 266/287, 219/121.110
International Classes:
E21B7/15; E21B7/14