Title:
Wear of bit indicator
United States Patent 2669871

Inventors:
Arthur, Lubinski
Publication Date:
02/23/1954
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Assignee:
Arthur, Lubinski
Primary Class:
Other Classes:
702/34, 703/3, 703/7, 173/20, 73/152.490
International Classes:
E21B12/02; E21B44/00; E21B12/00