Drilling brass safely For drilling free-cutting brass and similar ductile, grab-prone nonferrous alloys, which drill helix/rake configuration is commonly recommended to prevent the tool from digging in?

Introduction / Context:
Brass and some bronzes can “grab” a drill due to their machining behavior. Tool geometry adjustments reduce the tendency to self-feed and jam, improving safety and hole quality.

Given Data / Assumptions:

• Material is free-cutting brass (or similar).
• Conventional twist drills can dig in with excessive rake.
• Goal is stable cutting and controlled chip formation.

Concept / Approach:
Reducing effective rake at the cutting edge mitigates grabbing. This can be achieved by using straight-flute (zero helix) drills or by dubbing/grinding a small flat to reduce rake on a standard twist drill. The intent is to stabilize cutting forces and prevent self-feeding.

Step-by-Step Solution:
Identify the problem: excessive rake causes the tool to pull into soft ductile material.Select geometry: zero helix (straight flute) or zero rake edge by dubbing.Apply: drill brass with controlled feed; avoid aggressive helix.

Verification / Alternative check:
Shop practice widely recommends straight-flute or modified rake drills for brass; manufacturers offer specific “brass” drills with reduced rake.

Why Other Options Are Wrong:
(b) Low helix helps but zero helix is the standard recommendation. (c) High helix increases the grabbing tendency. (d) Geometry does matter. (e) Reverse helix is not standard for drilling.

Common Pitfalls:
Failing to deburr; using excessive feed as the drill breaks through; not supporting thin stock to avoid snatch.

Final Answer:
Zero helix angle (straight-flute or zero rake)