Saturday, November 22, 2025

Too Flexible Endmill

Why was my rectangle not completely square?  I do not mean in the corners where a round emdmill necessarily guarantees the corner will be limited by the diameter of the endmill.  Then I watched the endmill cutting circles.  It was definitely bending.

This is a Kodiak 1/8" diameter, 3" long endmill, made in USA.  This is a tradeoff issue. The extra length means deeper reach, but also it can bend a little.  This also makes it less likely to break when overloaded.  I am now using my Taiwanese Speed Tiger end mills which are 1" long.  They seem to flex less.  Again, this is a question that requires a level of knowledge by the machinist that I just starting to reach.  Do you need the deeper reach?  If so, slower feed rates to reduce flex, or a shorter endmill.

The flex doubtless increases vibration, making the endmill holder set screws less effective.  I need to put a flat on the SpeedTiger endmill shank too.

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