Issued Patents 1989
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4873895 | Manufacture of rotary drill bits | John D. Barr, John R. Smart | 1989-10-17 |
| 4862977 | Drill bit and cutter therefor | John D. Barr, Terry R. Matthias | 1989-09-05 |
Showing 1–2 of 2 patents
| Patent # | Title | Co-Inventors | Date |
|---|---|---|---|
| 4873895 | Manufacture of rotary drill bits | John D. Barr, John R. Smart | 1989-10-17 |
| 4862977 | Drill bit and cutter therefor | John D. Barr, Terry R. Matthias | 1989-09-05 |