Substitutability of Drills and End Mills in Specific Machining Scenarios

When a Drill Bit Meets a Milling Cutter: Emergency Tool Solutions for Atypical Conditions

In feedback from overseas customers, we have noticed that small and medium-sized machining workshops often face the dilemma of "temporary tool shortages." This article explores the feasibility of substituting high-speed steel cobalt (HSS-E) and solid carbide tools in non-standard conditions based on their characteristics, providing overseas buyers with emergency machining references.

Innate Structural Differences (Differentiation Entry Point)

Hidden Geometric Properties of Cutting Edges

• Helix Angle Advantage: The drill bit’s helix angle (25°-35°) offers chip evacuation benefits. When substituting for a milling cutter in deep slot machining, it can help reduce aluminum adhesion. (Test case: A Φ6 solid carbide drill bit machining a 5052 aluminum keyway with compressed air assisting chip evacuation.)
• Axial Cutting Strength: The end relief angle (8°-12°) of a milling cutter enhances axial cutting capability, performing better than standard twist drills in thin sheet stack drilling. (Mexican customer feedback: A 4-flute flat-end milling cutter successfully drilled through a 10-layer stainless steel shim stack, each layer 0.5mm thick.)

Fatal Weakness of Neck Strength

Stress Concentration Risk: Compared to milling cutters of the same diameter, the transition fillet radius of drill shanks is 30%-50% smaller. This makes drills prone to stress concentration at the fillet when used for side milling. (Attached metallographic analysis: Microcrack initiation in an M35 drill under a lateral load of 300N.)

Boundary of Material Substitution (Technical Breakthrough Point)

Scenario-Based Substitution Matrix

Compensation Strategies for Machining Parameters (Value-Added Point for Customers)

Speed Conversion Formula

Equivalent Milling Speed = Standard Drill Speed × (Drill Helix Angle / Milling Cutter Helix Angle)⁰·⁵

(Brazilian customer verification: When machining ABS with a Φ8 drill bit, using 1.2 times the normal speed improved surface roughness.)

Optimization of Tool Paths

It is recommended to use a "spiral progressive" approach instead of conventional reciprocating milling to reduce instantaneous lateral load on the drill edges. (Turkish auto parts factory case: Drill bit machining aluminum heat sink slots improved efficiency by 40%.)

The Feasibility Code of Tool Interchangeability

Shape Defines Function

• Drills Resemble Twists: Their spiral flutes excel at chip evacuation, making them suitable for deep slot machining in aluminum. (Like using a straw to drink bubble tea—the pearls don’t clog the straw.)
• Milling Cutters Resemble Knives: Their flat-end design allows for planar cutting, providing better stability than drills for temporary hole-making. (Like using a kitchen knife tip to poke small holes in thin wooden sheets.)

Material Hardness Comparison

Three Practical Scenarios for Tool Interchangeability

One Tool for Two Jobs: Saving Tool Change Time

• Drilling + Chamfering: Use a 140° pointed drill; after drilling, lightly press and rotate twice at the hole entrance to create a 0.5mm chamfer. (Like outlining with a pencil and refining with an eraser.)
• Slotting + Positioning: A flat-end milling cutter can first cut a shallow slot, then use its tip to mark an accurate positioning hole. (German customer test: Processing circuit board brackets saved 15% processing time.)
• Thin Sheet Machining: A two-flute milling cutter can be used as a drill for stainless steel sheets under 2mm thickness. (Key technique: Reduce speed by 30%, feed per revolution 0.02mm.)

Dangerous Operations to Avoid

• ⚠️ Side milling deep slots over 3 times the drill diameter with a standard drill. (Like trying to draw straight lines on a wall with an electric drill.)
• ⚠️ Using a milling cutter as a deep hole drill (over 5 times diameter). (Like making a sprinter run a marathon.)

Three Practical Substitution Techniques

Using a Drill as a Milling Cutter

• Applicable Scenario: Shallow slotting not exceeding 2 times the drill diameter
• Technique: Increase speed by 20%, reduce per-pass cutting depth by half (Like outlining carefully with a ballpoint pen.)
• Case Study: A Brazilian automotive supplier used a Φ5 drill to mill motorcycle bracket slots, saving 2 hours of tool waiting time.

Using a Milling Cutter as a Drill

• Applicable Scenario: Positioning holes on thin sheets
• Technique: First mark a shallow indentation, then gradually drill deeper (Like using a screwdriver tip to pierce an eggshell.)
• Warning: Stop immediately for thicknesses above 3mm.

One Tool for Dual Use

• Recommended Tool: Flat-bottom drill bits (capable of both drilling and chamfering)
• Test Data: Processing 100 parts saved 15 minutes of tool change time.

Three-Tier Risk Control Measures

• Primary Alert (Acoustic Monitoring): Issue an overload warning when machining noise exceeds 8kHz.
• Intermediate Alert (Chip Morphology): Stop immediately if deep blue curled chips appear in stainless steel machining.
• Ultimate Alert (Torque Fluctuation): Use a simple current sensor to monitor spindle load variations.

Conclusion

Tool substitution is like using a Swiss Army knife in emergencies—it works temporarily but is not a long-term solution. We provide both high-quality specialized tools and safe emergency machining techniques, ensuring your workshop maintains productivity at all times.