Mike Tyson once said:
“Everyone has a plan, until they get punched in the mouth.”
The same could be said when discussing the runout of an endmill assembly. As soon as one tooth of that endmill makes contact with the workpiece, it will deflect the entire endmill and when it exits, the endmill will rebound past its original centerline. That prompts another quote, this time from Sir Isaac Newton:
“For every action, there is an equal and opposite reaction.”
In other words a toolholder’s touted “close to zero” runout doesn’t survive the first revolution of the endmill in a cut. Claims that improving runout alone will automatically improve tool life are misleading. If the spindle speed (and resulting tooth impact interval) is not in time with this back and forth, deflection and rebounding cycle, the tool is running out in the cut, not matter what it measures at rest. Of course, minimizing runout is a good practice to create a robust repeatable process, IF you know its dynamic behavior.
“Everyone has a plan, until they get punched in the mouth.”
The same could be said when discussing the runout of an endmill assembly. As soon as one tooth of that endmill makes contact with the workpiece, it will deflect the entire endmill and when it exits, the endmill will rebound past its original centerline. That prompts another quote, this time from Sir Isaac Newton:
“For every action, there is an equal and opposite reaction.”
In other words a toolholder’s touted “close to zero” runout doesn’t survive the first revolution of the endmill in a cut. Claims that improving runout alone will automatically improve tool life are misleading. If the spindle speed (and resulting tooth impact interval) is not in time with this back and forth, deflection and rebounding cycle, the tool is running out in the cut, not matter what it measures at rest. Of course, minimizing runout is a good practice to create a robust repeatable process, IF you know its dynamic behavior.
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