Feed Rate vs Cutting Speed in CNC Machining: The Complete Guide

Blog / Feed Rate vs Cutting Speed in CNC Machining: The Complete Guide

Aug 21,2025

Getting to Know Feed Rate and Cutting Speed in CNC Machining

Why Feed Rate and Cutting Speed Matter

(mellowpine)

When you're running a CNC machine, two settings can make or break your results: feed rate and cutting speed. These numbers influence how quickly you can remove material, the lifespan of your cutting tools, and the quality of the finish on your parts. But it's easy, especially when you're just starting out, to mix them up or assume they mean the same thing.

At JLCCNC, we see this mix-up all the time when clients send in CAD files. It's one reason we review every project before production, making sure feed and speed settings are optimized for both the material and the machine. Getting them right can save you money, reduce cycle times, and help you hit your tolerances every time.

In this guide, we'll walk through the difference between feed rate and cutting speed, explain how to figure them out, share charts you can reference, and give you real-world tips for setting them correctly on your next CNC project.

What is Cutting Speed?

(Differencebox)

Think of cutting speed as the pace at which the very tip of your tool sweeps across the surface of your material. We usually measure it in meters per minute (m/min) or surface feet per minute (SFM). The “right” cutting speed changes depending on what you're machining and the tool you’re using.

For example:

Mild steel might use a cutting speed of 30-40 m/min with HSS tools.
Aluminum may be machined at 150-300 m/min with carbide tooling.
Plastics often require much slower speeds to avoid melting.
In CNC machining, setting the right CNC cutting speed helps extend tool life and achieve a clean finish. At JLCCNC, our CAM programmers factor this into every job, matching cutting speed to material data for consistent, repeatable results.

What is Feed Rate?

(Differencebox)

Feed rate, on the other hand, is all about how quickly the tool pushes forward into the material. It can be measured as:

mm/rev (millimeters per revolution)
mm/min or inches/min (linear feed rate)

It's more than just speed, feed rate controls the chip load, which is the thickness of material each tooth of the tool slices off in a single revolution. That means it can make or break machining efficiency.

Example:

In milling, cranking the feed rate too high can overload the tool, leading to chatter, poor finishes, and a very bad day for your cutter.
Too low, and you risk rubbing instead of cutting, which dulls tools faster.

When JLCCNC receives a file, we check if the part geometry will require adjustments to feed rate, especially for thin walls, small features, or delicate materials. This ensures machining is efficient without risking damage.

Feed Rate vs Cutting Speed

Aspect	Cutting Speed	Feed Rate
Definition	Speed of tool's cutting edge over material	Speed of tool's advance into material
Units	m/min or SFM	mm/rev, mm/min, in/min
Purpose	Optimizes tool-material interaction	Controls chip load and machining pace
Effect	Affects tool wear and surface finish	Affects cycle time and part quality

Common beginner mistake: Setting both high without considering material or tool limits. At JLCCNC, we often adjust both settings for clients before starting production, ensuring they complement each other.

How to Calculate Cutting Speed and Feed Rate

These cutting speed and feed formulas form the foundation of machining calculations. JLCCNC’s quoting tool automatically applies these formulas when you upload your CAD file, so you don’t have to guess at the numbers.

Cutting Speed Formula (Metric)

V = cutting speed (m/min)
D = tool diameter (mm)
N = spindle speed (RPM)

Feed Rate Formula

Vf = feed rate (mm/min)
N = spindle speed (RPM)
fz = feed per tooth (mm)
Z = number of teeth on cutter

If you want parts machined to spec without worrying about all these calculations, upload your CAD file to JLCCNC and relax.

Cutting Speed & Feed Rate Charts

Cutting Speed Chart (Metric & Imperial)

Material	Cutting Speed (m/min)	Cutting Speed (SFM)	Notes
Aluminum Alloys	150 – 300	500 – 1000	Carbide tools can run at higher speeds.
Mild Steel (Low Carbon)	30 – 50	100 – 165	Increase with coated carbide.
Stainless Steel	20 – 40	65 – 130	Requires good coolant to prevent work hardening.
Tool Steel (Annealed)	20 – 35	65 – 115	Reduce speed for hardened conditions.
Brass	90 – 200	300 – 650	Machines well at high speeds.
Bronze	60 – 120	200 – 400	Adjust based on alloy type.
Cast Iron	20 – 60	65 – 200	Gray iron tolerates higher speeds than ductile iron.
Plastics (Nylon, ABS)	100 – 200	325 – 650	Avoid heat buildup, keep tools sharp.
Titanium Alloys	20 – 30	65 – 100	Keep speeds low, use rigid setup, lots of coolant.

Feed Rate Chart (Metric & Imperial)

Material	Feed per Tooth (mm/tooth)	Feed per Tooth (inch/tooth)	Notes
Aluminum Alloys	0.05 – 0.15	0.002 – 0.006	Larger chip loads possible with rigid setups.
Mild Steel (Low Carbon)	0.04 – 0.12	0.0015 – 0.005	Reduce slightly for small-diameter cutters.
Stainless Steel	0.03 – 0.10	0.001 – 0.004	Keep feeds moderate to reduce work hardening.
Tool Steel (Annealed)	0.03 – 0.08	0.001 – 0.003	Lower end for finishing passes.
Brass	0.05 – 0.15	0.002 – 0.006	Handles aggressive feeds well.
Bronze	0.04 – 0.12	0.0015 – 0.005	Watch for tool deflection on gummy alloys.
Cast Iron	0.04 – 0.12	0.0015 – 0.005	Feeds depend on brittleness of alloy.
Plastics (Nylon, ABS)	0.05 – 0.20	0.002 – 0.008	Avoid melting, moderate speeds with higher feeds.
Titanium Alloys	0.03 – 0.08	0.001 – 0.003	Keep chip load steady to avoid rubbing.

JLCCNC's machinists use reference charts like these daily, adjusting numbers for each tool, material, and machine.

Tip: We recommend starting with the lower end of the range for prototypes and adjusting upward for production runs

Factors Affecting Optimal Cutting Speed & Feed Rate

Factor	Feed Rate	Cutting Speed
Definition	The speed at which the tool advances into the workpiece (mm/rev, mm/min).	The speed of the tool's cutting edge moving across the material's surface (m/min, SFM).
Impact on Tool Life	Too high feed → faster tool wear from heavy chip loads. Too low feed → rubbing, heat buildup.	Too high speed → thermal wear and tool edge breakdown. Too low speed → inefficient cutting, work hardening in some metals.
Effect on Surface Finish	High feed → rougher finish, visible feed marks. Low feed → smoother finish (up to a point).	High speed → generally smoother finish if feed is correct. Low speed → risk of tearing or poor surface quality.
Chip Formation	Controls chip thickness and load. Large feed → thicker chips. Small feed → thin chips.	Influences chip temperature and shape; higher speeds create hotter, more curled chips.
Cutting Forces	Higher feed → greater cutting forces on tool and machine.	Higher speed → less cutting force per tooth but higher heat generation.
Direction of Chips	Primarily influenced by feed direction and toolpath.	Influenced by cutting edge geometry and rotational speed.
Cycle Time	Higher feed → faster material removal, shorter cycle times.	Higher speed → faster cutting per revolution, potentially shorter cycle times if feed is matched.
Heat Generation	Higher feed generates mechanical stress heat.	Higher speed generates more frictional heat at the tool-workpiece interface.
Machine Load	Directly increases load on spindle drive and tool rigidity.	Less effect on spindle torque but more on thermal limits.

Cutting speed recommendations vary significantly by material type. Our CNC machining materials guide breaks down the ideal speeds and feeds for metals, plastics, and composites.

Common Problems and How to Fix Them

Poor surface finish: Reduce feed, increase speed.
Excessive tool wear: Lower speed, check coolant.
Chatter or vibration: Adjust both feed and speed, check setup rigidity.

JLCCNC clients benefit from our in-house process adjustments, we solve these issues before they happen.

FAQ

Q: What is cutting speed in CNC machining?

A: It's how quickly the cutting edge of a tool travels across the surface of the material. You'll usually see it measured in meters per minute (m/min) or surface feet per minute (SFM).

Q: And what about feed rate?

A: Feed rate describes how fast the tool moves forward into the workpiece, often measured in millimeters per revolution (mm/rev) or millimeters per minute (mm/min).

Q: How do I figure out the right feed rate and cutting speed?

A: You can work it out using the formulas mentioned earlier, or simply upload your design to JLCCNC's quoting tool — it does the math for you.

Q: Can using the wrong settings ruin my part?

A: Unfortunately, yes. Settings that are too high or too low can lead to rough surfaces, premature tool wear, or parts that don't meet spec.

Q: Does JLCCNC adjust these settings for every job?

A: Definitely. Our team checks each project and fine-tunes the feed and speed based on the material, tooling, and finish you're aiming for.

Final Tips for Choosing the Right Feed and Speed

Check tool manufacturer's recommendations.
Test and adjust in small steps.
Use CNC toolpath simulation to verify settings.
Our team will recommend the best feed rate vs cutting speed for your material and application, and handle the machining from start to finish.