Choosing drill helix for aluminum machining When drilling aluminum and other ductile, free-cutting non-ferrous alloys, which helix characteristic is preferred for the twist drill to improve chip evacuation and reduce built-up edge?

Introduction / Context:
Aluminum tends to produce long, continuous chips and can form built-up edge at the tool tip. Drill flute geometry, particularly the helix angle, critically affects chip evacuation and cutting temperature.

Given Data / Assumptions:

• Ductile, gummy materials such as aluminum and its alloys.
• Conventional twist drills with flutes and point geometry optimized for non-ferrous materials.

Concept / Approach:
A higher helix angle improves chip lifting and evacuation from the hole, decreases rubbing, and promotes a more positive effective rake along the cutting lips. This reduces the tendency for built-up edge and improves surface finish.

Step-by-Step Solution:
Identify material behavior: long, ductile chips need efficient evacuation.Select geometry: high helix angle increases chip flow capacity of flutes.Outcome: cooler cutting, less BUE, better hole quality → choose high helix.

Verification / Alternative check:
Manufacturers offer “bright-finished, high-helix aluminum drills” specifically for this purpose, confirming the selection.

Why Other Options Are Wrong:

• Zero or low helix (A/B) hampers chip lifting and can cause clogging.
• (D) ignores the strong influence of helix on chip flow.
• Negative helix (E) is not used for standard drilling.

Common Pitfalls:
Using standard steel drills with low helix on aluminum, leading to chip packing and poor finish; insufficient coolant or pecking cycles in deep holes.

Final Answer:
high helix angle