Drill point geometry for hard alloy steels When drilling harder alloy steels, how should the drill point angle be selected relative to the standard 118° point used for mild steel?

Introduction / Context:
Drill point angle directly influences cutting edge strength, thrust, chip flow, and heat generation. Harder materials demand stronger cutting edges and improved support near the chisel edge to reduce wear and edge breakdown.

Given Data / Assumptions:

• Work material is a harder alloy steel.
• Standard point angle for general purpose drilling in mild steel is about 118°.
• Goal is improved edge strength and reduced chisel-edge rubbing.

Concept / Approach:
Increasing the point angle (for example to 130–140°) thickens the wedge near the cutting edges, improving strength and heat dissipation. It also reduces the length of the chisel edge and the included angle at the lips, which helps when thrusting into hard materials. Conversely, smaller angles suit softer materials and thin sheets where easy penetration is preferred.

Step-by-Step Solution:
Identify requirement: stronger cutting edge for hard alloys.Modify geometry to increase wedge angle: choose a point angle more than 118°.Result: reduced wear and better life when drilling tough/hard steels.

Verification / Alternative check:
Tool catalogs list heavy-duty and cobalt twist drills for hard steels with 130° or 135° split-point geometries to strengthen lips and lower walking.

Why Other Options Are Wrong:
118° is general-purpose for mild steel; less than 118° weakens the edge and increases rubbing. “Any angle” and 90° ignore well-established practice.

Common Pitfalls:
Using a sharp but weak angle on hard steels, leading to rapid chipping; not providing adequate coolant or peck cycles.

Final Answer:
More than 118°