Many people have questions regarding end mills and why they break. Below are the things to always check during milling out your 80% lower project. 

  • Always apply cutting fluid prior to milling each layer. WD-40 or similar lubricants may be used instead of cutting fluid.
  • The end mill and lower must be coated with a lubricant at all times to prevent damage to the end mill and lower.
  • Set the router to the maximum RPM speed if using a variable speed router. 
  • Make sure the end mill is completely stopped before removing and inserting the end mill into the lower.
  • Make sure the end mill is centered in the pilot hole and not touching the lower before starting the router.
  • Keep a firm grip and use 2 hands on the router at all times. 
  • Maintain moderate downward pressure on the router at all times. 
  • Mill in small clockwise circles, about the size of a US Dime.
  • Move the router slowly and smoothly. 
  • The slower the router is moved, the better the finish.
  • Make shallow cuts. The less material cut per pass, the better the finish.
  • To avoid breaking and premature dulling of end mills, move slowly, and take shallow cuts.