General CNC Wood/Metal/Plastic/Composites Router Bit Information

Several decent links:

– This from the Fab Academy: Router Bit Basics

– Decent basic description of the material types used in the above: Onsrud Cutter Tools (

–’s description of various cutters: CNC Router Bits


Cutting MDF/Plywood/Laminates:

 – MDF is abrasive due to glue content and should be cut with at least carbide cutters. HSS will die very quickly with MDF, plywood and other similar materials.

  – Using a Compression Endmill is best on laminates. It cuts both up and down, which leaves both surfaces clean, but is designed so that it is done in ONE pass. If the machine cannot manage a single pass, another style of bit needs to be used.

– Next best is straight flute cutters. Upcutting alone (for good-one-side plywood would leave the bottom side clean, much better for clearing chips, but will mar the top surface and require extra cleaning up. In addition, an upcutting spiral bit can also (with aggressive feeds) actually pull the work material off the table if it is not secured well enough.

– A downcutting bit would save the top of the material, but risks re-cutting the chips and damaging the lower side.

– According to some sources, Plywood likes to splinter when cutting in climb milling, so conventional is better. Having said that, I have seen representatives state that one should do a test cut, and see which is a cleaner cut (the waste material or non-waste), and adjust the cutting method to accommodate that. In my own recent use, I had a better finish in climb (Home Depot 1/2 inch SPF plywood; had lots of voids). This site states Climb Milling is better with wood. *shrug*.

– It is said that high speed steel with cut smoother than carbide, but as with anything, that depends on feed rates, condition and type of tool; I have used straight flute carbide and had (to me) acceptable finish on plywood (conventional worked better with that bit, as climb caused splintering)

– Several sources state the same methodology should be used in wood as metal; use a rouging tool to remove the bulk of the material at a high rate of speed, and use a finishing tool to complete the job. This will extend the life of both tools, but will require more than one pass, and possibly more than one Gcode session.