CNC Intro
Introduction to CAD, CAM and cutting data for CNC milling. For the machines themselves, see CNC Machines.
Getting started
New to CNC: start on the Carvera Air. The NYC CNC YouTube channel covers most basics in short, well-made videos.
New to CAD: get a free hobby licence for Fusion. It takes you from model to G-code (the file the machine runs). More on CAD.
Tools and consumables
End mills and cutting fluid are your own responsibility. For metal you also need lubricant/coolant (typically T-röd).
There's a box of shared tools ("Allas verktyg") you may use. If you break one, please replace it with something.
Some end mills are sold in the makerspace webshop.
Post-processor (LinuxCNC)
For the LinuxCNC machines (Betongsuggan, Portalfräsen):
General → Arc radius: on
Built-in → Allow helical moves: off
Arc radius errors in LinuxCNC usually mean wrong post-processor settings.
Feeds and speeds
Chip load is what matters
Chip load (feed per tooth) is the most important number. Get it from the tool manufacturer, then calculate feed:
Feed (mm/min) = rpm × chip load (mm) × number of flutes
Example: 6000 rpm, 3-flute, 1000 mm/min → 1000 / 6000 = 0.167 mm per revolution → / 3 = 0.055 mm chip load.
Too thin: the tool rubs instead of cutting — heat and fast wear.
Too thick: too much force — chatter and broken tools.
Plastics tolerate a wider range of feeds; metals need tighter control and slower feed at the same rpm.
Fusion calculates feed automatically if you enter rpm and feed per tooth for your tool.
Surface speed matters for tool life in industry, but for hobby use, keeping the right chip load is enough. Video
Climb vs conventional milling
Use climb milling by default on CNC — it gives better-defined chips and less wear. Video
Depth and width of cut
An end mill cuts along its whole flute length, not just the tip. Spreading the load over more of the flute makes the tool last longer: take deep cuts with smaller stepover rather than shallow full-width cuts.