Vent: Feeds and speeds debate after my spindle crash in Toledo

I was running a 1/4 inch end mill on a job at a Toledo shop and dropped the RPM from 12k to 8k to save tool wear, then it grabbed and snapped the holder clean, so is it better to trust the machine's default settings or your own gut when the finish looks fine?

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markh853d ago

The default settings exist because someone already did the math on that exact tool and material combo, so going off feel when you haven't changed anything else is basically asking for trouble. You dropped the RPM for no real reason if the finish was already good, and that lower speed changes how the flutes bite, which is exactly when chips load up and snap things. Your gut told you saving tool wear was worth it, but the machine was telling you the correct cutting speed for that setup, and one of those sources has actual data behind it. Next time, trust the numbers over the vibe until you can change the tool or the material, because a snapped holder costs way more than a little extra wear on a $15 end mill.