CNC Spirograph

Step 5: Selecting the Bit

On our homemade CNC machine, is a Porter Cable Trim Router. It will accept ¼” shank bits, and with collets, will size down to 5/32” and 1/8” shank tooling.  As I had selected Baltic birch plywood, I chose a ¼”shank 1/8” end mill. This means it is strong (thicker shank), and will cut 1/8” wide with a square bottom.
Our router only goes one speed in rotation and maxes out at 25 linear inches per minute, so the only control we have is how deep it cuts per pass, and the inches per minute speed it travels thru the material.  Before any machinery is turned on, install the bit into the router you have. Be VERY careful, they are quite sharp. I wouldn’t know that, but there are a wide range of band aids and compresses readily available in our shop, just in case.