Support a long gundrill tube every ~40× the drill diameter to stop it whipping under load. Enter drill diameter and depth to get the recommended spacing and support count.
For L/D > 200:1, space supports closer (use the tight value) and consider vibration dampers. Dedicated machines have built-in steady rests and whip guides spaced along the axis.
| Drill dia | Standard spacing (~40×D) | Tight spacing (>200:1) |
|---|---|---|
| 3 mm | 120 mm | 90 mm |
| 5 mm | 200 mm | 150 mm |
| 10 mm | 400 mm | 300 mm |
| 20 mm | 800 mm | 600 mm |
| 40 mm | 1,600 mm | 1,200 mm |