Recurring Speeds & Feeds Calculator
Calculate spindle RPM and table feed rate for CNC milling and drilling. Enter your tool diameter, cutting speed, and feed per tooth to optimize your machining parameters.
Machining Parameters
Enter your tooling details to calculate optimal speeds and feeds
Select your preferred measurement system for all inputs and outputs.
Diameter of the cutting tool in mm or inches.
Recommended surface speed for your workpiece material.
Number of cutting teeth on the tool.
Thickness of material removed per tooth in mm or inches.
Machining Results
Spindle speed, feed rate, and parameter breakdown
Enter your machining parameters above and click Calculate Speeds & Feeds to reveal your spindle RPM and feed rate.
Common Cutting Speeds
Cutting speeds vary significantly based on the workpiece material and the type of cutting tool (HSS, Carbide, Coated). Below are typical starting ranges for various materials.
| Workpiece Material | SFM (Imperial) | m/min (Metric) | Feed per Tooth (Carbide) |
|---|---|---|---|
| Aluminum (Soft) | 800 – 1,500 | 240 – 450 | 0.002 – 0.005 in |
| Mild Steel (Low Carbon) | 100 – 150 | 30 – 45 | 0.001 – 0.003 in |
| Stainless Steel | 50 – 100 | 15 – 30 | 0.0005 – 0.002 in |
| Cast Iron | 80 – 120 | 24 – 36 | 0.001 – 0.003 in |
| Titanium Alloys | 40 – 60 | 12 – 18 | 0.0005 – 0.0015 in |
| Brass / Bronze | 150 – 300 | 45 – 90 | 0.001 – 0.003 in |
| Plastics (Acrylic/Delrin) | 200 – 600 | 60 – 180 | 0.002 – 0.006 in |
| Hardened Steel (>45 HRC) | 40 – 80 | 12 – 24 | 0.0002 – 0.001 in |
Speeds & Feeds FAQ
Everything you need to know about calculating machining parameters, spindle speeds, and feed rates for CNC operations.
Speeds and feeds refer to the cutting speed (how fast the tool spins or moves across the material) and the feed rate (how fast the tool advances into the material). Properly calculating these parameters is critical for achieving good surface finish, maximizing tool life, and ensuring efficient material removal.
Spindle speed (RPM) is calculated using the formula: RPM = (Cutting Speed × 1000) / (π × Tool Diameter) for metric, or RPM = (Cutting Speed × 12) / (π × Tool Diameter) for imperial. The cutting speed is determined by the workpiece material and tooling.
Feed rate (table feed) is calculated by multiplying the spindle speed (RPM) by the number of flutes (teeth) on the cutter, and then multiplying that result by the feed per tooth (chip load). Formula: Feed Rate = RPM × Number of Flutes × Feed per Tooth.
SFM (Surface Feet per Minute) measures the linear speed at which the cutting edge of the tool passes across the surface of the workpiece. RPM (Revolutions Per Minute) measures how many full rotations the spindle makes in one minute. SFM remains constant for a given material, while RPM changes depending on the tool diameter.
Harder materials require lower cutting speeds to prevent excessive heat generation and premature tool wear. For example, aluminum can be machined at very high speeds (800+ SFM), while hardened steel or titanium requires much lower speeds (40-80 SFM) to maintain tool integrity.
Feed per tooth, often called chip load, is the thickness of the material removed by each cutting flute (tooth) as it passes through the workpiece. It is usually measured in inches per tooth (IPT) or millimeters per tooth (mm/tooth). Maintaining the correct chip load is essential to prevent tool deflection and work hardening.