How to Prevent Chip Packing When Drilling Stainless Steel

Chip packing is one of the most common and costly problems encountered when drilling stainless steel. Many machining engineers have experienced sudden tool breakage, poor hole surface finish, or dramatically reduced tool life caused by chips accumulating inside the hole.

Unlike carbon steel, stainless steel produces long, ductile chips that are difficult to break and evacuate. Without proper chip control, these chips quickly clog the flutes, leading to unstable cutting conditions.

Why Chip Packing Occurs When Drilling Stainless Steel

Understanding the material behavior of stainless steel is essential for preventing chip packing:

• High ductility: Chips are long and continuous, making them difficult to break.

• Work hardening: Improper cutting causes the material to harden rapidly.

• Low thermal conductivity: Heat concentrates at the cutting edge.

• High friction: Chips tend to adhere to the tool and hole wall.

These characteristics make stainless steel particularly sensitive to inadequate chip evacuation.

Common Problems Caused by Chip Packing

• Sudden carbide drill breakage

• Scratched or damaged hole walls

• Inconsistent hole size and tolerance

• Severely shortened tool life

Preventing chip packing is therefore not optional—it is critical for process stability and cost control.

Effective Ways to Prevent Chip Packing

1. Use the Right Carbide Drill Geometry

Drill geometry plays a decisive role in chip formation and evacuation. Optimized point angles, flute profiles, and margin designs help control chip flow. High-precision drills designed specifically for stainless steel, such as our UPX Series solid carbide drill bits,    offer improved centering and stable cutting behavior.

2. Prefer Coolant-Through Carbide Drills

Internal coolant delivery is one of the most effective ways to prevent chip packing. Coolant-through carbide drills force chips out of the hole while simultaneously cooling the cutting zone. ICF Series coolant-through carbide drill bits    are specifically designed for stainless steel drilling applications.

3. Control Feed Rate—Not Just Spindle Speed

Excessively low feed rates produce thin, stringy chips that are more likely to tangle and clog flutes. A properly calculated feed rate promotes chip thickness and improves chip breaking.

4. Use Dedicated Deep Hole Drills for High L/D Ratios

When drilling holes with an L/D ratio greater than 8×D, chip evacuation becomes increasingly difficult. Standard drills are often insufficient. For such applications, dedicated deep hole tools like our  LXD Series deep hole carbide drill bits provide enhanced rigidity and stable chip evacuation.

5. Rethink Peck Drilling

While peck drilling is often used to reduce chip packing, it can increase friction and work hardening in stainless steel. With modern CNC machines and coolant-through drills, continuous drilling is often more effective.

Application-Based Drill Selection

• Thread pre-drilled holes: UPX Series / ICF Series

• Deep holes in stainless steel: LXD Series with internal coolant

• Small or micro holes: ZMD Series micro carbide drills