CNC Router Bit Size

Pros select why to choose a larger or smaller bit. July 3, 2005

I am in the process of installing my first CNC router and have a question about tooling. How come you guys all use 1/2" or 3/8" router bits instead of 1/4"? It would seem to me that 1/4" would leave more material on the deck and less dust in the collector. Also the vacuum should hold parts better if the kerfs are 1/4" instead of 1/2". Is breakage an issue with 1/4" bits? Or do they wear out faster?

Forum Responses
(CNC Forum)
From contributor J:
With 3/8 compression, I can cut at almost any speed in my 1/2 birch nests without breakage. But more importantly, the 3/8 kerf allows room for dadoes and grooves to cut past the radius of the cutters without cutting into a neighboring piece.

From contributor G:
With a .250 tool you will not be machining as quickly as a .375 or a .500 tool. The gullet space from a 1/4" to a 1/2 tool is deeper, which allows for more chip evacuation, thus increasing tool life.

Your yield will be much better on the 1/4 vs. 1/2 tool. Depending on your needs, a 1/4" tool may be the way to machine, or a .375 may be the way to go.