Feeds & Speeds
Onefinity CNC · PWNCNC air-cooled spindle
Dial in cuts across wood species and bit types. Pick a material, bit, and diameter — the calculator gives feed rate, plunge, depth of cut, and stepover, with an aggressiveness read so you can start conservative and work up. Numbers are hobby-CNC starting points synthesized from Amana/Onsrud chip-load charts, PWNCNC, and the Onefinity community — always verify by ear and eye.
Calculator
Feed = RPM × flutes × chip load
Upcut spiral: Best chip evacuation; can fuzz the top edge of the workpiece.
Softwood (pine, cedar): Cuts easily; can fuzz/tear — a downcut or a light finish pass cleans edges.
Feed = RPM × flutes × chip load = 18,000 × 2 × 0.0050 = 180 IPM. Starting point — verify by ear/eye and adjust. Rated 8k–24k RPM, but treat ~12k as the practical floor — torque falls off sharply below it. Set via the VFD (Modbus from the Onefinity controller).
Chip-load reference
Feed per tooth (inches), 2-flute basis — the numbers behind the calculator
| Material | 1/8" | 1/4" | 3/8" | 1/2" | Start RPM | DOC / pass |
|---|---|---|---|---|---|---|
| Softwood (pine, cedar) | 0.002–0.004 | 0.004–0.007 | 0.006–0.011 | 0.009–0.015 | 16–18k | 1× Ø |
| Hardwood (oak, maple, walnut) | 0.002–0.003 | 0.003–0.006 | 0.005–0.009 | 0.007–0.013 | 18,000 | 0.4× Ø |
| Plywood / laminated | 0.002–0.004 | 0.004–0.007 | 0.006–0.010 | 0.008–0.014 | 18,000 | 0.75× Ø |
| MDF | 0.003–0.005 | 0.005–0.008 | 0.007–0.012 | 0.010–0.016 | 16–18k | 0.75× Ø |
| Acrylic / plastics | 0.001–0.003 | 0.003–0.006 | 0.004–0.008 | 0.005–0.010 | 12–16k | 0.4× Ø |
Ranges are conservative starting points. Scale for flute count. When cutting a full-width slot, halve the DOC (both flanks engaged).
Bit guide
Pick the right geometry for the cut
Upcut spiral
2FLGeneral cutting, pockets, slots — pulls chips UP and out
Best chip evacuation; can fuzz the top edge of the workpiece.
Downcut spiral
2FLClean top edges, thin veneers, tabs
Pushes chips DOWN — clean top surface but poor evacuation; take shallow passes.
Compression spiral
2FLPlywood & laminated sheets — clean both faces
Up-cut tip + down-cut body; first pass must be ≥ the up-cut flute length.
Straight / O-flute
1FLAcrylic & plastics (O-flute), general wood (straight)
O-flute (1 flute) clears gummy plastic chips; less clean than spiral in wood.
Ballnose
2FL3D contour carving & finishing passes
Feed is measured at full diameter; use small stepover (~8–12%) for smooth 3D.
V-bit (60°/90°)
2FLV-carve lettering, chamfers, engraving
Effective cutting diameter changes with depth — let the software drive feeds.
Surfacing / spoilboard
2FLFlattening slabs & spoilboards (large Ø)
Big diameter → low RPM (12–15k) and slower feed; light DOC, ~40–50% stepover.
Cut-type playbook
How settings shift by operation
Profile / cutout
Use tabs to hold parts; conventional milling for cleaner outer edges; add a finish pass leaving ~0.02" then a full-depth cleanup.
Pocketing
~40–50% stepover for roughing; ramp or helix into the material instead of straight plunging; leave a finish wall pass.
Engraving / V-carve
Let the CAM set feeds from the effective diameter; light DOC; sharp V-bit; slow down on hardwood to avoid burning.
3D finishing (ballnose)
Small stepover (8–12% Ø) for smoothness; climb-mill the finish pass; more passes beat one aggressive pass.
Surfacing / flattening
Large surfacing bit, RPM 12–15k, ~0.01–0.03" DOC, 40–50% stepover, moderate feed; multiple light passes for a glassy top.
Wood by application
What to reach for — matched to the job
Fine furniture & heirloom
Strong, stable hardwoods with rich grain that age beautifully and finish to furniture quality.
CNC · Sharp bits + light DOC cut clean; keep the feed up on maple/cherry or they scorch.
Outdoor / weather-exposed
Natural rot & moisture resistance (cedar/oak/teak) — or HDPE for a zero-maintenance, fully weatherproof part.
CNC · Cedar is soft (downcut for clean edges); teak is oily & abrasive (dulls bits); HDPE machines superbly with an O-flute.
Cutting boards & food-contact
Closed-grain hardwoods resist bacteria and are food-safe with the right finish. Avoid open-grain (red oak) and softwoods.
CNC · End-grain is tough on tooling — light passes. HDPE = O-flute, keep chips clearing to avoid melt.
Signs & lettering
Even surfaces take crisp V-carve detail; acrylic/Corian/PVC for weatherproof outdoor signage.
CNC · MDF V-carves razor-sharp but is dusty; a sharp 60° V-bit and light DOC give clean lettering.
3D relief carving
Soft, even, tight grain carves clean with a ballnose and minimal tear-out — basswood is the standard.
CNC · Small stepover (8–12% Ø) + sharp ballnose; a raster + perpendicular pass kills scallops.
Inlay & contrast work
Bold, stable color contrast for inlays and intarsia.
CNC · Exotics can be brittle/abrasive — climb-mill the finish pass for crisp edges; some dust is a sensitizer, wear protection.
Jigs, fixtures & spoilboards
Flat, stable, cheap and dimensionally consistent — ideal for repeatable fixtures and a sacrificial spoilboard.
CNC · Compression bit for clean plywood edges; MDF/phenolic dull bits fast but hold tolerance well.
Paint-grade cabinetry & millwork
Smooth, affordable, and take paint cleanly without prominent grain telegraphing through.
CNC · Poplar fuzzes — use a downcut or a finish pass; seal/prime MDF edges before painting.
Toys & kids' items
Durable, splinter-free, smooth, and safe with food-grade finishes.
CNC · Round over all edges; skip softwoods that dent and splinter.
Prototyping & one-offs
Cheap and forgiving for test fits and quick iterations before committing good stock.
CNC · Fast to cut; MDF is best for dimensional test fits (no grain movement).
Material cheat-sheet
Hardness, grain, machinability & cost — sortable at a glance
| Material | Type | Janka | Grain | CNC | Cost | Best for | Notes |
|---|---|---|---|---|---|---|---|
| Hard maple | Hardwood | 1450 | Closed, fine | 4/5 | $$ | Boards, furniture, toys | Premium light wood; burns if the feed is too low. |
| Walnut | Hardwood | 1010 | Open–medium | 5/5 | $$$ | Furniture, inlay, boards | Machines beautifully; rich dark color. Dust can sensitize. |
| Cherry | Hardwood | 950 | Closed, fine | 5/5 | $$$ | Furniture, boards | Cuts clean but scorches easily; darkens with age. |
| White oak | Hardwood | 1350 | Closed-ish | 4/5 | $$ | Outdoor, furniture | Rot-resistant & tough; closed grain is food-friendlier than red oak. |
| Red oak | Hardwood | 1290 | Open, bold | 4/5 | $$ | Furniture, trim | Prominent grain; open pores — not for cutting boards. |
| Ash | Hardwood | 1320 | Open, straight | 4/5 | $$ | Furniture, handles | Strong and light-colored; bends well. |
| Poplar | Hardwood | 540 | Closed, plain | 5/5 | $ | Paint-grade, prototyping | Cheap and soft; fuzzes on edges. Green/gray streaks. |
| Basswood | Hardwood | 410 | Very even | 5/5 | $ | 3D carving, signs | The carving benchmark — holds fine detail, little tear-out. |
| Padauk | Hardwood | 1970 | Open, coarse | 3/5 | $$$ | Inlay / accent | Vivid orange-red; abrasive, staining dust. |
| Purpleheart | Hardwood | 2520 | Closed | 2/5 | $$$ | Inlay / accent | Very hard — can burn and gum; stunning purple. |
| Western red cedar | Softwood | 350 | Straight | 4/5 | $$ | Outdoor signs, siding | Soft, aromatic, rot-resistant; can fuzz — sharp bits. |
| Pine | Softwood | 380–870 | Knotty | 4/5 | $ | Prototyping, rustic | Cheap; knots/resin cause tear-out and pitch buildup. |
| Baltic birch ply | Sheet good | — | Void-free plies | 5/5 | $$ | Jigs, boxes, furniture | Clean edges with a compression bit; consistent, no voids. |
| MDF | Sheet good | — | None | 4/5 | $ | Spoilboards, signs, painted | V-carves crisp; very dusty & abrasive — seal edges before paint. |
| Melamine / particleboard | Sheet good | — | None | 3/5 | $ | Shelving, fixtures | Chips easily — use downcut/compression; dulls bits. |
| HDPE | Plastic / composite | — | None | 5/5 | $$ | Outdoor, boards, jigs | O-flute, keep chips clearing; weatherproof and food-safe. |
| Acrylic (cast) | Plastic / composite | — | None | 3/5 | $$ | Signs, displays | Melts if rubbing — O-flute, moderate RPM, keep the feed high. |
| Corian / solid surface | Plastic / composite | — | None | 4/5 | $$$ | Durable signs, inlay | Machines like a dense plastic; holds excellent detail. |
| Phenolic / Richlite | Plastic / composite | — | None | 3/5 | $$$ | Jigs, tough parts | Very abrasive (carbide required); waterproof and stiff. |
Janka = hardness in lbf (higher = harder). CNC = machinability (5 = cleanest/easiest). Sheet goods & plastics have no Janka rating.
Dial it in
Reading the machine — and the PWNCNC spindle
Signs & rules of thumb
- ▸Onefinity hobby baseline is ~40–60 IPM; work up toward 100 as you dial in — don't start at a calculator's max.
- ▸Burning/scorching = feed too slow or RPM too high — the bit is rubbing. Speed up the feed or drop RPM.
- ▸Fine powder instead of chips = rubbing (heat + fast bit wear). You want real chips.
- ▸Chatter / deflection / rough walls = too aggressive — reduce DOC or feed, shorten stickout, re-clamp.
- ▸Rough with conventional milling (safer on a hobby gantry); finish with a light climb pass for a cleaner edge.
- ▸Chip thinning: on light finish passes (radial engagement < ½ bit Ø), raise the feed or the tool rubs and burns.
- ▸Keep the air-cooled spindle at ~12k RPM or above — torque falls off sharply below it.
Spindle
Rated 8k–24k RPM, but treat ~12k as the practical floor — torque falls off sharply below it. Set via the VFD (Modbus from the Onefinity controller).