CNC Feeds & Speeds Calculator
Feeds & speeds
Material setup
Geometry
Machine constraints
Feeds & speeds
Cutting parameters
Material removal
Understanding your result
RPM — Spindle speed. Keep within your machine's range; cap at spindle max if needed.
Feed rate — How fast the tool moves through the material (mm/min). Higher = faster cutting but more tool stress.
Chip load — Material removed per tooth per revolution. Too low = rubbing and heat; too high = tool breakage risk.
Surface speed — Peripheral speed at the cutter edge. Used to derive RPM from diameter.
Start conservative and increase feed if the cut sounds clean. Burning, fuzzing or chatter means something is wrong.
How feeds & speeds work
What is chip load?
Chip load (mm per tooth) is how much material each flute removes per revolution. Feed rate = Chip load × Flutes × RPM. If chip load is too low, the tool rubs instead of cutting — heat builds up and you get burning. Too high and the tool is overloaded.
Cutter types at a glance
Upcut / Downcut spiral — Standard for through-cuts and pockets. Upcut evacuates chips; downcut gives cleaner top edges. Compression — Best for veneered boards and MFC; clean edges both sides. Bullnose — Rounded bottom for 3D carving and smooth fillets. V-bit — Engraving, signs, inlays; use lower chip load and light stepdown to protect the tip. Chamfer — Angled edges and deburring.
Why MDF burns
MDF is resin-bonded fibre. When chip load drops too low, the cutter rubs rather than shearing. Friction heats the resin, which chars. Keep chip load in range and use adequate feed — slow feed causes burning.
Why compression cutters matter
Upcut pulls chips up (good evacuation, rough top surface). Downcut pushes down (clean top, chips pack in slot). Compression combines both — upcut in the middle, downcut at top and bottom — ideal for veneered and melamine-faced materials.
How to tell if settings are wrong
Burning — Chip load too low or feed too slow. Fuzzing — Tear-out; reduce chip load or use downcut/compression. Chatter — Tool or machine overloaded; reduce feed or stepdown. Rapid tool wear — Too aggressive; reduce chip load or surface speed.
Why metric matters
CNC programming is metric-first. Feed in mm/min, chip load in mm/tooth, and surface speed in m/min give consistent, repeatable results. Imperial conversion is available for compatibility.
Frequently asked questions
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What does the CNC feeds & speeds calculator do?
It recommends spindle RPM, feed rate (mm/min) and chip load for CNC routing in wood and panel materials. You select material, cutter type, diameter and flutes to get workshop-safe baseline settings.
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Why are the recommendations conservative?
We prioritise tool life and safety. Start with these values and increase feed if the cut sounds clean. It's easier to speed up than to replace a broken tool or repair a burnt workpiece.
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What is chip load?
Chip load is the thickness of material each flute removes per revolution, in mm per tooth. Too low causes rubbing and burning; too high overloads the tool. The calculator keeps you in a safe range.
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When should I use a compression cutter?
Compression cutters are ideal for veneered boards, melamine-faced chipboard (MFC) and materials where you need a clean edge on both top and bottom. They combine upcut and downcut geometry.
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When should I use a V-bit or bullnose?
V-bits are for engraving, signs and inlays — use lower chip load and light stepdown to protect the sharp tip. Bullnose bits have a rounded bottom for 3D carving, smooth fillets and edges; they behave similarly to downcut spirals for chip evacuation.
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Can I use imperial units?
Yes. Toggle imperial units to see feed in in/min and chip load in in/tooth. Inputs remain in mm; outputs convert. Surface speed stays in m/min as it's the industry standard.
