Helix angle in drill – how it affects cutting, and applications
The helix angle in drill has a big difference on the cutting efficiency. The higher the drill helix angle, the greater the force pushing chips axially out of the hole. However, the higher the drill helix angle, the smaller the cross sectional area of the drill and the weaker it is.
| DRILL TYPE | DRILL HELIX ANGLE | APPLICATION |
|---|---|---|
| High helix angle (alias fast spiral drill) | 40 | Used for high feed rate, low cutting speed. On soft non-ferrous metals like brass, aluminum, magnesium, zinc, plastics. |
| Standard helix angle | 30 | Has optimal chip ejection and strength of drill cross section. Most widely used. |
| Low helix angle | 12 | Used with high spindle speeds on (alias slow spiral drill) hard to drill materials, because it has high cross section strength. |
| Straight drill | 0 | Used on low tensile strength materials like copper and brass and on sheet metal, because it does not have a tendency to ‘pull in’ the material (and thereby bend it, if it is a sheet or of thin cross section). |
Action point
The general rule is that the deeper the hole, the higher the helix angle must be, for better chip removal. The higher the cutting forces (harder, stronger material), the lower the helix angle must be.
