Center Drill Dimensions
Center drills are used to make a dimple to ensure that a drill doesn’t “walk” when it first contacts the flat face of a piece of metal. We also use them to drill the end of a cylindrical part we will be turning with a lathe.
| Size | Body Dia (A) | Drill Dia (D) | Drill Length (C) | OAL (L) |
|---|---|---|---|---|
| 00 | 1/8 | 0.025 | 0.030 | 1 1/8 |
| 0 | 1/8 | 1/32 | 0.038 | 1 1/8 |
| 1 | 1/8 | 3/64 | 3/64 | 1 1/4 |
| 2 | 3/16 | 5/64 | 5/64 | 1 7/8 |
| 3 | 1/4 | 7/64 | 7/64 | 2 |
| 4 | 5/16 | 1/8 | 1/8 | 2 1/8 |
| 5 | 7/16 | 3/16 | 3/16 | 2 3/4 |
| 6 | 1/2 | 7/32 | 7/32 | 3 |
| 7 | 5/8 | 1/4 | 1/4 | 3 1/4 |
| 8 | 3/4 | 5/16 | 5/16 | 3 1/2 |
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Bell Type Dimensions
| Size | Body Dia (A) | Drill Dia (D) | Bell Dia (E) | Drill Length (C) | OAL (L) |
|---|---|---|---|---|---|
| 11 | 1/8 | 3/64 | 0.1 | 3/64 | 1 1/4 |
| 12 | 3/16 | 1/16 | 0.15 | 1/16 | 1 7/8 |
| 13 | 1/4 | 3/32 | 0.2 | 3/32 | 2 |
| 14 | 5/16 | 7/64 | 0.25 | 7/64 | 2 1/8 |
| 15 | 7/16 | 5/32 | 0.35 | 5/32 | 2 3/4 |
| 16 | 1/2 | 3/16 | 0.4 | 3/16 | 3 |
| 17 | 5/8 | 7/32 | 0.5 | 7/32 | 3 1/4 |
| 18 | 3/4 | 1/4 | 0.6 | 1/4 | 3 1/2 |