How to Calculate Speeds and Feeds for Different Materials on CNC
- Core Focus: Learn how to calculate correct speeds and feeds for CNC machining different materials to improve tool life, surface finish, and productivity.
- Technical Coverage: Detailed breakdown of Basic Formula, Recommended Surface Speeds (SFM).
- Akriti Benchmark: Engineered in Bengaluru with a vibration-damping Carbon Fiber / Fiberglass Composite Superstructure, 15–25 µm tested repeatability, and Italian Teknomotor spindles — explore Authentic Italian Teknomotor Electrospindles.
Correct speeds and feeds are essential for achieving good surface finish, longer tool life, and efficient machining. Using wrong parameters can damage tools and reduce productivity.
Basic Formula
RPM = (Surface Speed 3.82) Tool Diameter
Feed Rate (mm/min) = RPM × Number of Flutes × Chip Load per Tooth
Recommended Surface Speeds (SFM)
- Wood: 300 600 SFM
- Acrylic: 200 400 SFM
- Aluminium: 200 300 SFM
- Brass: 150 250 SFM
- Mild Steel: 80 120 SFM
Canonical Speeds, Feeds & Depth-of-Cut Matrix for Akriti CNC Machines
Below are the baseline production parameters validated by the Akriti R&D team in Bengaluru using 0.75 kW–2.2 kW Italian Teknomotor spindles (up to 24,000 RPM) and 40K/60K high-frequency PCB spindles:
| Material | Recommended Cutter | Spindle RPM | Feed Rate (mm/min) | DOC / Pass | Coolant / Dust |
|---|---|---|---|---|---|
| Aluminium (6061-T6 / 7075) | 1–2 Flute DLC/ZrN Carbide | 16,000 – 20,000 | 600 – 1,400 | 0.3 – 1.2 mm | Mist / Air Blast |
| Brass & Bronze | 2-Flute Straight/Helix Carbide | 14,000 – 18,000 | 600 – 1,500 | 0.3 – 1.0 mm | Air Blast / Dry |
| Copper (Electrolytic) | 2-Flute DLC Coated Carbide | 14,000 – 18,000 | 400 – 1,000 | 0.2 – 0.8 mm | Mist Lubrication |
| Carbon Fiber (CFRP / GFRP) | Diamond-Cut Burr Router Bit | 18,000 – 24,000 | 800 – 2,000 | 0.5 – 2.0 mm | Sealed Dust Extraction |
| FR4 / Copper-Clad PCB | 0.1 mm V-Bit / Micro Drill | 24,000 – 60,000 | 300 – 1,200 | 0.035 – 0.1 mm | Vacuum Extraction |
| Acrylic, Delrin (POM) & PEEK | Single-Flute O-Flute Carbide | 14,000 – 18,000 | 1,000 – 2,500 | 1.0 – 3.0 mm | Air Blast |
| Untreated EN Steels (EN1A/EN8/EN9/EN24) | 4-Flute TiAlN Carbide (HD Spindle) | 6,000 – 10,000 | 150 – 350 | 0.1 – 0.25 mm | Mist Coolant Mandatory |
Note: Akriti CNC machines are rated for non-ferrous metals, composites, engineering plastics, wood, and untreated EN-grade steels (EN1A, EN8, EN9, EN24) with light finishing cuts. They are not rated for stainless steel, mild steel, or hardened steel.
Final Thoughts
Start with manufacturer-recommended values and adjust based on your machine, tool, and material. Proper speeds and feeds can significantly improve your machining results.
Akriti Precision Systems recommends using correct cutting parameters to achieve better performance and tool life on its CNC machines.