Diamond-coat or carbide tooling
FR4's glass fibre is abrasive enough to destroy plain tooling - diamond-coated bits last for repeated work; carbide wears but works for occasional jobs.
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How to cut PCB and FR4 on a CNC router
The three things that matter most:
- FR4's glass fibre is intensely abrasive and destroys ordinary tooling fast - use diamond-coated bits, or carbide and expect wear.
- The dust is toxic: fine glass-fibre and resin particulate that you must not breathe. Extract at the cutter and wear a respirator.
- This is the desktop-mill and precision audience - fine tooling, rigid setup, light consistent cuts.
Feeds & speeds calculator, pre-filled for pcb / fr4
Set your cutter diameter, flutes and RPM and read the feed rate and chip load. This is the same tool as the pcb / fr4 feed & speed page, which carries the full chip-load reference table.
Recommended feed rate
144.6IPM3,672 mm/min
Plunge rate
28.9 IPM
734 mm/min
Chip load
0.0765 mm
0.0030″ / tooth
Chip load bandIn range
0.051 mm0.102 mm
Your chip load is 0.0765 mm per tooth, which is within the recommended 0.051–0.102 mm range for pcb / fr4 with a 6.35 mm upcut spiral.
Table range for pcb / fr4 at 6.35 mm0.051–0.102 mm
Depth factor (cut is 0.47× diameter)×1.000
Geometry factor (upcut spiral)×1.00
Feed = 24,000 × 2 × 0.0765 mm3,672 mm/min
PCB / FR4. FR4 is glass fibre in epoxy and it is brutally abrasive - treat cutters as consumables. The dust is a respiratory hazard; extract it at the source and do not dry-sweep it.
Upcut spiral. The baseline the published charts assume. Chips are lifted clear of the cut, which keeps heat out of the workpiece at the cost of tear-out on the top surface.
Which bit to use
The glass reinforcement in FR4 is abrasive enough to wear a carbide edge quickly, so diamond-coated tooling is the durable choice for repeated work; carbide works but wears. Fibre-optic and PCB-specific end mills and engraving bits are made for exactly this. Match the tool to the fine features PCB work usually needs.
Feeds, speeds & depth of cut
Keep cuts light and consistent - FR4 doesn't fight back like metal, but it grinds tooling away, so the goal is controlled, repeatable passes rather than speed. Use the calculator's FR4 settings below as a starting point and prioritise tool life and precision over material removal rate.
Workholding
PCB stock is thin and must sit dead flat and rigid, because the features are fine and any lift ruins registration. A vacuum or a flat, well-clamped sacrificial base is standard; this is precision work where the setup's flatness matters as much as the tool.
Chip evacuation & cooling
The critical issue is the dust, not chips: FR4 releases fine glass-fibre and resin particulate that is a genuine inhalation hazard. Extract right at the cutter and wear a respirator - and clean the abrasive dust off the machine, because it wears everything it touches.
Reading your results
Good FR4 milling holds fine features cleanly with a sharp tool; ragged edges or lost detail usually mean the tool has worn on the glass fibre - swap it. Because the material is abrasive rather than tough, degradation shows up as tool wear over time more than as sudden failure.
Common mistakes
- Using ordinary HSS or worn carbide - the glass fibre destroys it. Diamond-coat for repeated work.
- Ignoring the dust - FR4 particulate is toxic. Extract and wear a respirator.
- Letting the stock flex - fine PCB features need a dead-flat, rigid setup.
Tooling & parts for pcb / fr4
The consumables a fix like this usually calls for. Prices are live; we may earn a commission on a purchase, which never affects what we recommend.
In stock
Dust extraction
FR4 dust is toxic glass-fibre and resin particulate - extract at the cutter, wear a respirator, and clean the abrasive dust off the machine.
Genmitsu 65mm & 69mm CNC Dust Shoe · or browse all options
$44.99
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Frequently asked
- What bit should I use to mill FR4 or PCB?
- For repeated work, diamond-coated tooling, because FR4's glass fibre is abrasive enough to wear plain carbide quickly. Carbide works for occasional jobs but expect it to dull. Use PCB-specific end mills and engraving bits for the fine features, and keep the stock dead flat.
- Is FR4 dust dangerous?
- Yes. Milling FR4 releases fine glass-fibre and cured-resin particulate that you should not inhale. Use dust extraction right at the cutter, wear a respirator, and clean the abrasive dust off the machine afterward, since it wears guides and bearings.
Related
Feed & speed for PCB / FR4 (the tool) →Desktop CNC mills, compared →How to cut aluminium →All material guides →
Tooling and technique are drawn from manufacturer documentation and established references; starting ranges are exactly that - the exact feed and chip load for your cutter come from the calculator above, never invented here.