| HK diamond core drill bits material | Recommended drill head pressure (lbs.)* |
|---|---|
| Fiberglass | 10 to 15 lbs. |
| Limestone & Marble Stone | 12 to 18 lbs. |
| Glass, Ceramic & Porcelain China | 12 to 18 lbs. |
| Ceramic/Porcelain Wall Tile | 15 to 20 lbs. |
| Stone Style Porcelain Floor Tile | 18 to 30 lbs. |
| Granite Stone | 18 to 30 lbs. |
*WARNING: Drill press arms leverage hand pressure by a factor of about 6 to 8. So 2 lbs. of hand pressure on the drill press arm will apply about 14 lbs. of pressure to the drill head.
If a drill bit develops yellow, brown, blue or black ‘burn marks’ around the tip, it is an indication of extreme heat caused by the excessive drill speed or by too much pressure on the drill. Impact type “hammer drills” should never be used with diamond drills as they have no benefit and will cause the tip of the bit to mushroom or split.
If a hole is being drilled completely through a piece of material, it is also important to “lighten up” considerably on the pressure when the drill bit is near the back of the material. This reduces chipping or fracturing on the back of the material when the bit emerges from the back. Using a similar “backer” material may also help prevent accidental and damaging breakthroughs.