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| All Patents in class 175/392 | |||||
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| Picture | Number | Date | Patentee | Title | |
 | 47,812 | May 23, 1865 | W.W. Grier, R.H. Boyd | Improved drill-bit | |
| 627,659 | Jun. 27, 1899 | F.B. Spry | Expanding Auger | ||
| 2,863,640 | Dec. 09, 1958 | G.A. Petersen | Offset Boring Head for Auger | ||