Precision holes are critical. In high-performance parts—especially in aerospace, medical, and automotive—every micron counts. If your drilled holes aren't meeting spec, CNC reaming may be the missing piece.
Work with Rapid Model to solve your toughest hole quality problems.
What Is Reaming—And Why CNC Reaming Is Different
Reaming is a precision machining process used to slightly enlarge and refine pre-drilled holes. It improves diameter accuracy, roundness, and surface finish—beyond what drilling alone can achieve.
CNC Reaming vs. Traditional Methods
Compared to manual or semi-automatic methods, CNC reaming offers repeatability and tight control over speed and feed. It allows for micron-level tolerances in high-volume production.
Reaming vs. Drilling vs. Boring: Tolerance Comparison
| Process |
Typical Tolerance |
Surface Finish (Ra) |
| Drilling |
±0.005" – 0.010" |
~3.2 – 6.3 µm |
| Boring |
±0.001" – 0.003" |
~1.6 – 3.2 µm |
| Reaming |
±0.0005" – 0.001" |
~0.4 – 1.6 µm |
Where CNC Reaming Matters Most
Precision reaming is essential in applications where hole tolerance is mission-critical:
Medical Implants: Ti64 bone screws with Ø0.5mm reamed holes
Aerospace Fasteners: Tight-fitting wing spar bores
Fuel Injection Systems: Smooth, concentric flow paths
Rapid Model’s Reaming Capabilities
We deliver micron-level accuracy using high-performance tools and engineering insight.
Precision: Achievable tolerances of ±0.0002" (Ø0.008") using AlTiN-coated reamers
Material Expertise: Chrome-nickel alloys, titanium, PEEK
Tooling Partner: Harvey Tool® certified reamer selection
Our CNC Reaming Process: Step-by-Step Accuracy
1. Smart Pre-Drilling
We follow the 90-94% Rule—reamers work best when holes are pre-drilled to 90–94% of the final diameter.
Case Study: Reducing scrap rate by 32% in auto valve bodies through optimized pilot drilling.
2. Intelligent Tooling
Straight-Flute vs. Spiral-Flute: Spiral preferred for blind holes
AlTiN vs. Uncoated: High-temp alloys benefit from coated reamers
3. Process Tuning
Quick-reference charts for cutting speeds and feeds by material:
| Material |
Speed (SFM) |
Feed (IPR) |
| Aluminum |
300–500 |
0.004–0.006 |
| Mild Steel |
80–120 |
0.002–0.004 |
| Composites |
100–150 |
0.003–0.005 |
Advanced vibration-damping helps achieve mirror-like surface finishes.
When Reaming Becomes Mission-Critical
Medical: Ø0.5mm micro-reaming with customized coolant delivery
Aerospace: On-machine CMM verification of wing spar bores
Automotive: Reamed sealing surfaces in brake calipers with chip evacuation optimization
Beyond Basics: Advanced Reaming Strategies
Avoid Costly Mistakes
Common failure modes include:
Wavy Holes – due to unstable fixturing
Bellmouths – caused by poor pre-drilling
Reamer Breakage – due to incorrect feed rate
Real Fix: A pump client reduced over-sized bore defects by switching to balanced AlTiN-coated reamers and adjusting RPM.
Smarter Monitoring: We implement IoT sensors for in-process reaming quality feedback.
Industry Applications
Medical Devices
Aerospace Components
Hydraulic & Pneumatic Systems
Automotive Assemblies
Precision Pumps & Valves
Frequently Asked Questions
How much stock should I leave for reaming?
Typically 0.1–0.3 mm, depending on material and reamer type.
Can reaming straighten a crooked hole?
No. It refines but doesn’t correct misalignment—proper pre-drilling is key.
What’s the cost difference between reaming and boring?
Reaming is faster and more cost-effective for consistent small-diameter holes.
What’s the maximum length-to-diameter ratio for micro-reaming?
Up to 5:1 is safe; longer requires custom tool support.
