How to Cut Wood With a CNC Machine

• 1
  Key takeaways
• 2
  What to prepare before you cut wood with a cnc machine
• 3
  Pick the cutter before you pick the speed
• 4
  Feeds, speeds and depth of cut for wood
• 5
  Workholding and dust control decide the result
• 6
  When wood routing is the wrong process
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  Step by step: cutting wood on a CNC machine
• 8
  Cutter and parameter guide for common wood work

Routing wood rewards preparation. A machine that holds ±0.005 mm in aluminium will still produce fuzzy edges in oak if the blank moves or the cutter is dull. Before any program runs, decide three things: which wood, which face stays visible, and how the part will be held. Those answers drive tool geometry, feed rate and fixture design.

Wood is not a homogeneous block. Earlywood and latewood cut differently, and grain direction flips from face grain to end grain across a single contour. A cutter that leaves a clean edge along the grain can lift fibres when it crosses the end grain. That is why the same program can pass on one blank and fail on the next.

Moisture content matters more than most shops admit. Kiln-dried hardwood at 6–8% moisture machines cleanly and stays stable after cutting. Material straight off a truck at 12–15% will move after the clamps come off, and the part may twist within days. Let the blank acclimate in the shop before you commit to a tolerance callout.

Decide the tolerance you actually need. Wood moves with humidity, so ±0.1 mm is realistic for a routed hardwood part, while ±0.005 mm belongs to metal work. Telling the shop the real requirement keeps the process honest and the price sane.

The cutter decides chip evacuation and which face survives. A two-flute spiral up-cut pulls chips upward and leaves a clean top surface, which suits through-cut parts where the top face is cosmetic. A down-cut pushes chips down, protecting the top face but packing dust into the kerf on deep passes.

Compression spirals combine both: up-cut geometry at the tip, down-cut at the shank. They are the standard choice for plywood and melamine, where both faces must stay clean. They cost more and need a deeper first pass to engage both zones, so they are a poor fit for 3 mm sheet.

Flush trim and template bits follow an existing profile. Use them when a part is nested against a jig or when you are trimming veneer after glue-up. Their bearing or shank rubs the template, so the template has to be harder than the workpiece, typically MDF sealed with lacquer or a phenolic sheet.

Solid carbide lasts far longer than high-speed steel in abrasive species such as teak or MDF. Coated cutters help in MDF and particle board, where resin builds heat. For most hardwoods and softwoods, an uncoated two-flute carbide spiral between Ø3 mm and Ø12 mm covers the majority of work.

Start from chip load, not from a feed number copied off the internet. Chip load is the thickness of material each cutting edge removes per revolution. For a Ø6 mm two-flute carbide cutter in hardwood, a chip load of 0.1–0.2 mm per tooth keeps heat down and produces a clean edge.

Feed rate follows from chip load: feed = chip load × flutes × RPM. At 18,000 rpm with two flutes and 0.15 mm chip load, the feed lands near 5,400 mm/min. If the machine or the fixture cannot hold that speed, reduce RPM instead of dropping the chip load too far, or the cutter will rub and burn.

Depth of cut should be conservative on the first pass. A common starting point is one times the cutter diameter for softwood and half the diameter for dense hardwood, with a finishing pass of 0.3–0.5 mm left on the walls. Full-depth single passes work in foam and soft pine but chatter in maple.

Ramp or helix into the cut rather than plunging straight down. A vertical plunge in hardwood loads the centre of the cutter where surface speed is lowest, and the tool will heat and dull. A 2–3° ramp angle spreads the load and keeps the chip load stable through entry.

A wood part that moves during the cut is scrap, no matter how good the program is. Vacuum tables hold full sheets well but lose grip as soon as you cut the perimeter and break the vacuum seal. Plan tabs or leave an onion skin of 0.3–0.5 mm so the part stays attached until the last operation.

For smaller blanks, screw the workpiece to a sacrificial MDF spoilboard from underneath, outside the finished profile. Double-sided tape works for thin panels when the tape covers most of the underside, but it releases with heat, so keep spindle speed and feed in a range that does not scorch the surface.

Clamps reach only the edges of the blank. On a 600 × 600 mm part, the middle can lift under cutter pressure even when the corners are tight. Add a mid-span hold-down or reduce depth of cut in the centre region. Listen for a change in pitch: it usually means the part has started to move.

Dust extraction is a safety and quality item, not an accessory. Airborne fine dust from MDF and hardwood is a health hazard, and chips left in the kerf are re-cut, which dulls the tool and burns the edge. A 100 mm hose at the shoe plus a downdraft table covers most routing setups.

Routing stops making sense when the drawing demands metal-level tolerance on a wood part. A ±0.05 mm callout on a 400 mm oak rail will fail on humidity alone, even if the machine holds the number on the day of cutting. If the function needs that tolerance, switch the material or redesign the joint.

Deep narrow pockets are another limit. A pocket 40 mm deep and 6 mm wide needs a long, thin cutter, and wood has little stiffness to resist deflection. The tool will bend, the wall will taper, and the finish will burn. Either open up the pocket or split the part.

Very small batches of flat panels are often faster on a panel saw or a waterjet-cut template. Routing wins when the part has contours, pockets, 3D relief or repeated features where one program replaces many manual setups.

Finally, some species machine badly. Highly abrasive tropical hardwoods dull carbide quickly, and resinous softwoods gum up cutters. In those cases, plan shorter tool life into the quote rather than assuming the same cutter will run all day.