Drill steel centralizer for coal drill
United States Patent 2788194
US Patent References:
Centralizer for drill steels
- - 1776594

Drill steel guide
- - 2350661


Inventors:
Hale, Ralph F.
Publication Date:
04/09/1957
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Assignee:
JOY MFG CO
Primary Class:
173/147
Other Classes:
175/323, 175/421, 175/170, 173/37
International Classes:
E21B19/24; E21B19/00