Free CNC Feeds and Speeds Calculator

Calculate optimal cutting parameters for CNC milling, turning, and routing. Get accurate RPM, feed rates, chip loads, and depth of cut recommendations for 50+ materials.

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50+ Materials Database

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Calculate Your Cutting Parameters

1Material Selection

Material Type *

2Tool Specifications

Tool Type *

Tool Diameter *

Number of Flutes *

Tool Coating *

Coatings increase speeds by 15-50% and tool life up to 5x

3Operation Parameters

Operation Type *

Machine Type *

Coolant / Lubrication *

Coolant can increase speeds 10-30% and extend tool life 50-100%

💡 Quick Tip: Start with recommended parameters and fine-tune based on your machine's performance. Listen for chatter (reduce speed/feed), watch chip formation (chips should be golden/silver, not blue/smoking).

Material Cutting Speeds Quick Reference

Surface speeds (SFM) for carbide tools with coolant

Material	Roughing (SFM)	Finishing (SFM)	Machinability	Notes
Aluminum
Aluminum 6061	800	1200	90%	Excellent machinability, use sharp tools
Aluminum 7075	600	900	85%	Harder than 6061, may work harden
Aluminum 2024	700	1000	87%	Good machinability, watch for stringy chips
Low Carbon Steel
Steel 1018	130	180	70%	Common mild steel, moderate feeds
Alloy Steel
Steel 4140	80	120	55%	Hard alloy steel, reduce speeds
Steel 4340	65	95	50%	Very hard, requires carbide tools
Stainless Steel
Stainless 304	70	100	45%	Work hardens quickly, keep cutting continuously
Stainless 316	60	90	42%	Difficult to machine, use coolant
Stainless 17 4ph	50	75	38%	Precipitation hardened, very tough
Titanium
Titanium Ti6al4v	60	90	35%	Low thermal conductivity, use flood coolant
Superalloy
Inconel 718	30	50	20%	Extremely difficult, ceramic tools recommended
Copper Alloy
Brass	400	600	95%	Excellent machinability, sharp tools for finish
Copper
Copper	250	400	80%	Soft and gummy, sharp tools essential
Cast Iron
Cast Iron Gray	100	150	65%	Abrasive, use dust collection
Engineering Plastic
Acetal Delrin	600	900	92%	Easy to machine, watch for heat buildup
Polycarbonate	500	750	88%	Sharp tools prevent melting
High-Performance Plastic
Peek	400	600	80%	Expensive material, optimize for minimal waste
Composite
Carbon Fiber	500	750	60%	Very abrasive, diamond-coated tools, dust hazard
G10 Fr4	400	600	70%	Fiberglass composite, abrasive, use ventilation

High Machinability (80-100%):

Easy to machine, high speeds possible, long tool life

Medium Machinability (50-79%):

Moderate difficulty, standard speeds, normal tool life

Low Machinability (<50%):

Difficult to machine, reduced speeds, short tool life

📝 Note: Values shown are for carbide tools with flood coolant. Reduce speeds by 20-30% for dry cutting or HSS tools. Increase by 15-35% for coated carbide (TiAlN, AlTiN, Diamond). Always start conservative and adjust based on results.

📚 Quick Start Guide

1. Select Your Material

Choose from 50+ materials including aluminum, steel, stainless, titanium, and plastics.

2. Enter Tool Specifications

Input tool diameter, number of flutes, and coating type for accurate results.

3. Set Operation Type

Choose roughing for material removal or finishing for surface quality.

4. Get Results

Receive RPM, feed rate, chip load, depth of cut, and optimization tips.

⚠️ Safety First: Always start with conservative parameters and test. Monitor machine performance and adjust as needed.

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How to Calculate Feeds and Speeds

Calculating optimal feeds and speeds is critical for CNC machining success. The right parameters maximize productivity, extend tool life, and ensure high-quality surface finishes. Our calculator uses industry-standard formulas and material-specific data to provide accurate recommendations.

Understanding the Core Formulas

1. Spindle Speed (RPM)

RPM = (Cutting Speed × 12) / (π × Tool Diameter in inches)

Or in metric: RPM = (Cutting Speed in m/min × 1000) / (π × Diameter in mm)

The spindle speed determines how fast the tool rotates. It's calculated based on the desired surface speed (SFM) and tool diameter. Smaller tools require higher RPM to achieve the same surface speed.

2. Feed Rate

Feed Rate = RPM × Number of Flutes × Chip Load

Feed rate is how fast the tool advances through the material. It depends on spindle speed, number of cutting edges (flutes), and the desired chip load per tooth.

3. Chip Load

Chip Load = Feed Rate / (RPM × Number of Flutes)

Chip load represents the thickness of material removed by each cutting edge per revolution. Too low causes rubbing and premature wear; too high risks tool breakage. Optimal chip load varies by material and operation type.

Material-Specific Considerations

Aluminum Alloys

• High speeds: 800-1200 SFM
• Sharp tools essential
• 2-3 flutes for roughing
• Use coolant or air blast

Stainless Steel

• Low speeds: 50-100 SFM
• Work hardens quickly
• Never let tool dwell
• Flood coolant mandatory

Mild Steel

• Medium speeds: 130-180 SFM
• Good machinability
• 4 flutes typical
• Coolant recommended

Engineering Plastics

• High speeds: 500-900 SFM
• Sharp tools prevent melting
• Single flute often best
• Air blast for chip removal

Optimization Strategies

For Faster Material Removal (Roughing)

• Maximize feed rate within machine capability
• Use larger diameter tools when possible
• Increase depth of cut (up to 1.5-2× tool diameter)
• Use coated carbide tools for higher speeds
• Employ climb milling for better chip evacuation

For Better Surface Finish (Finishing)

• Increase RPM (higher surface speed)
• Reduce feed rate and chip load
• Use more flutes (6-8 for finishing)
• Minimize radial depth of cut (5-10% stepover)
• Ensure tool is sharp and well-balanced

For Extended Tool Life

• Use appropriate coolant (flood coolant for difficult materials)
• Select TiAlN or AlTiN coatings for steel
• Reduce cutting speed by 10-15% from maximum
• Maintain proper chip load (avoid rubbing)
• Monitor tool wear and replace before catastrophic failure

Frequently Asked Questions

Feeds and speeds are the fundamental cutting parameters in CNC machining. "Speed" refers to the spindle speed (RPM) or surface speed (SFM), which is how fast the cutting tool rotates. "Feed" refers to the feed rate (IPM or mm/min), which is how fast the tool moves through the material. Together, they determine cutting efficiency, surface finish, tool life, and part quality. The right combination depends on material, tool type, operation, and machine capability.

CNC Machining Best Practices

Before Machining

✓ Verify workpiece material and hardness
✓ Inspect tool condition and coating
✓ Check tool holder taper cleanliness
✓ Ensure adequate workpiece clamping
✓ Set up coolant system properly
✓ Program work offsets accurately

During Machining

✓ Listen for unusual sounds (chatter, squealing)
✓ Watch chip formation and color
✓ Monitor spindle load percentage
✓ Check for vibration or deflection
✓ Verify coolant flow is adequate
✓ Be ready to stop if issues arise

After Machining

✓ Inspect part dimensions and surface finish
✓ Examine tool wear under magnification
✓ Document successful parameters
✓ Clean machine and work area
✓ Log tool life for future reference
✓ Note any adjustments made

Troubleshooting

✓ Chatter → Reduce RPM or depth of cut
✓ Poor finish → Increase RPM, reduce feed
✓ Blue chips → Reduce speed or add coolant
✓ Tool breakage → Check chip load and DOC
✓ Rapid wear → Verify speeds and coolant
✓ Deflection → Reduce tool overhang