Frequently Asked Questions
What is SFM in machining?
SFM (Surface Feet per Minute) is the speed at which the material moves past the cutting tool. It's determined by the material you're cutting and the tool material. Different materials have different recommended SFM values - for example, aluminum typically uses 200-400 SFM, while steel uses 80-150 SFM.
How do I calculate RPM from SFM?
RPM = (SFM × 3.82) / Tool Diameter. For example, if you're cutting aluminum at 300 SFM with a 0.5" end mill: RPM = (300 × 3.82) / 0.5 = 2,292 RPM.
What is IPM in CNC machining?
IPM (Inches Per Minute) is your feed rate - how fast the tool moves through the material. It's calculated from RPM, IPT (inches per tooth), and number of flutes: IPM = RPM × IPT × Number of Flutes.
What is Material Removal Rate (MRR)?
MRR tells you how much material you're removing per minute in cubic inches. It's calculated as: MRR = IPM × Depth of Cut × Width of Cut. Higher MRR means faster material removal, but requires more power and can reduce tool life.
What speeds and feeds should I use for aluminum?
For aluminum, typical SFM is 200-400, with IPT around 0.005 inches per tooth. Start conservative and work your way up based on your specific setup, tool condition, and coolant usage.
How do I calculate speeds and feeds for stainless steel?
Stainless steel requires slower speeds than aluminum. Typical SFM is 60-120, with IPT around 0.002 inches per tooth. Always use coolant and start with conservative parameters, especially for harder grades like 304 or 316 stainless.
What factors affect speeds and feeds?
Key factors include: material hardness, tool material (carbide vs HSS), tool condition (new vs worn), setup rigidity, coolant usage, and tool manufacturer recommendations. Always start conservative and adjust based on your specific conditions.