A Calculator To help With CNC Setups

I created a spreadsheet calculator tool to help understand the interactions between RPM, Feed Speed, Chip Loads, Bits and etc. Hopefully, it will be of some value to others struggling with all the terms. A very useful feature is the ability to compare two different spindles like the Makita vs. a speed-controlled spindle. If you choose to use it please use your best judgment until the recommended settings have been reviewed and tested. The instructions and download links are on my blogsite.


Thanx for sharing, my experience so far is that cnc router feeds and speeds are as much art as science.

some observations:

  • Single flute is great when you can find them

  • Most of the time you will be technically too low on chip load but if you’re not burning you tend to be okay.

  • After a while you can tell bad settings by the sound. Too deep and/or too fast is a horrible sound. Start a little shallow and slow and work up.

  • The most important thing with plastics and aluminum is cooling. Once things start to soften due to heat your screwed.

  • Like all rules of thumb, your mileage may vary.


Thanks so much for sharing this with us! You’ve done a great job putting a wealth of information together in an intuitive format. Sure beats the hand-written notes and trial-and-error approach!

Thank you Stephen. My goal was to have the information in one place to help understand the limits of your system. I am working on a paid version with some enhancements like compensating for chip thinning.
Beyond that I am starting to look look into the idea of an app. Excel is great but it does have limitations.

Let me know if you would like to stay informed.