Example Data Table
| Material |
Bit diameter |
Flutes |
RPM |
Chip load |
Feed estimate |
Depth |
Use case |
| Softwood |
6.35 mm |
2 |
18,000 |
0.10 mm |
3,960 mm/min |
3 mm |
Profile cut |
| Hardwood |
6.35 mm |
2 |
18,000 |
0.08 mm |
2,534 mm/min |
3 mm |
General routing |
| Plywood |
3.175 mm |
2 |
20,000 |
0.045 mm |
1,656 mm/min |
1.5 mm |
Small detail |
| MDF |
6 mm |
1 |
19,000 |
0.12 mm |
2,166 mm/min |
4 mm |
Pocket clearing |
Formula Used
Base feed: Feed = RPM × flutes × chip load.
Adjusted feed: Adjusted feed = base feed × material factor × feed override.
Chip thinning: If stepover is less than half the cutter diameter, factor = 1 / sin(acos(1 - 2ae / D)).
Final feed: Final feed = adjusted feed × chip thinning factor, capped by machine feed limit.
Surface speed: Surface speed = π × cutter diameter × RPM / 1000.
Material removal rate: MRR = feed × depth of cut × stepover / 1000.
Power estimate: Power = feed × depth × stepover × specific cutting energy / 60.
Machining time: Time = total cut distance / feed + plunge allowance.
How to Use This Calculator
Choose the closest wood material first. Enter cutter diameter, flute count, RPM, and target chip load from your tool supplier or shop notes.
Add stepover, depth of cut, toolpath length, work thickness, and machine limits. Use metric units where possible for cleaner CNC setup records.
Press the calculate button. Read the final feed rate, chip load check, power estimate, pass count, and machining time. Review all warnings before cutting.
Download the CSV for spreadsheets. Download the PDF for a job sheet. Test the result on scrap before using it on finished wood.
CNC Wood Router Feed Planning
A feed and speeds calculator helps turn guesswork into planned cutting data. Wood is forgiving, but it still burns, chips, tears, and overloads small cutters when settings are wrong. A good setup balances spindle speed, chip load, cutter diameter, flute count, depth of cut, and stepover.
Why Feed and Speed Matter
Chip load is the thickness removed by each cutting edge. If chip load is too low, the edge rubs instead of cutting. Heat rises and resin can build on the bit. If chip load is too high, the cutter may chatter, deflect, or snap. Feed rate connects chip load to RPM and flute count. That link makes it the main number used by the machine.
Wood Material Behavior
Softwood normally allows faster feed and deeper passes. Hardwood needs more control because grain changes can raise cutting force quickly. Plywood has glue lines and alternating grain. MDF cuts evenly, yet dust load is high. The calculator uses a material factor and specific cutting energy to estimate demand. These values are guides, not machine guarantees.
Advanced Setup Notes
Stepover changes chip thickness during profile or pocket work. Light radial engagement can reduce the actual chip thickness. The calculator applies chip thinning compensation for smaller stepovers. This helps prevent rubbing during finishing passes. Depth of cut and stepover also set material removal rate. That number gives a useful load comparison between jobs.
Using the Results Safely
Start with conservative settings on any new tool, wood, or fixture. Listen for chatter. Watch chip shape and surface finish. Clean chips mean the cutter is working. Brown dust, smoke, or squeal means feed or RPM needs adjustment. Check hold down strength before raising feed.
Practical Workflow
Enter cutter size, flutes, chip load, RPM, stepover, and depth. Add cut length and material thickness to estimate pass count and time. Compare the calculated feed with the machine limit. Review warnings before cutting. Save the CSV or PDF result for job notes. Run a short test slot first. Then adjust in small steps until the cut is clean, stable, and repeatable. Record the cutter brand, flute geometry, and moisture conditions. These details explain why one saved setup may differ from another board later.
FAQs
What is chip load?
Chip load is the thickness of material removed by one cutting edge during one revolution. It connects RPM, flute count, and feed rate.
Why does wood burn during routing?
Burning often happens when the bit rubs instead of cutting. Increase feed, reduce RPM, sharpen the cutter, or clear chips better.
Should hardwood use slower feed?
Hardwood often needs a more conservative feed because grain direction and density change cutting force. Test settings on scrap first.
What does stepover mean?
Stepover is the side distance between adjacent toolpaths. Lower stepover improves finish but can cause chip thinning and rubbing.
Why is chip thinning included?
Small radial engagement lowers actual chip thickness. Chip thinning compensation raises feed so the cutter still makes proper chips.
Can this replace toolmaker recommendations?
No. Use the calculator as a planning aid. Cutter geometry, machine rigidity, hold down, dust extraction, and wood condition still matter.
What feed should I use for a new bit?
Start below the calculated value. Cut a short test path. Then adjust feed and RPM until chips look clean and sound is stable.
Why download CSV and PDF results?
CSV helps compare jobs in spreadsheets. PDF gives a simple setup sheet for repeat routing, shop records, and operator notes.