Cut Threads vs Formed Threads for 10-24 Aluminum Internal Threads | Best Practice in CNC Machining

Introduction

In precision CNC machining, choosing the right threading method can significantly impact product performance, assembly experience, and long-term durability. For a recent internal 10-24 UNC threading project, we evaluated two common processes: thread cutting and thread forming (roll forming). To better understand the differences, we sectioned both threaded holes and inspected them under a projector for micro-structure comparison.

Thread Cutting (Cut Tapping)

Process
Material is removed to create thread profile.

Advantages

• Excellent for hard or brittle materials
• Lower torque during machining
• Clean and sharp thread profile
• Chips provide visible cutting feedback

Considerations

• Thread path can be slightly weaker due to material removal
• Requires chip evacuation
• Potential for burrs at entry/exit

Best for: general-purpose machining, wide material range, sharp thread profile needs

Observation in our test:
Cut threads created a sharper crest profile and smooth initial engagement, allowing screws to align and enter easily.

Thread Forming (Roll Forming / Extrusion)

Process
Threads are created by displacing and compressing material — not cutting it.

Advantages

• No chips — cleaner machining
• Stronger thread structure (work-hardening effect)
• Excellent for softer metals (e.g. aluminum, brass)
• Better fatigue resistance

Considerations

• Requires precise hole dimension control
• Higher tapping torque
• Threads are more rounded by design

Best for: high-strength thread applications, chip-free environments, softer materials

Observation in our test:
Formed threads showed rounded crests due to material flow. During assembly, screw entry required a slightly more careful alignment at the first thread engagement, which is normal in some forming cases and can be optimized further.

Visual Comparison

📷 Projector Inspection Images