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That is where i ge mine.
Arent that a little on the tight side? AFAIK I’ve seen 3.5 lbs mentioned as a good value.
Too tight may introduce some jagged motion meaning the bit may be doing equally jagged “bite sizes”.
The primary parameter for how fast one can go, ignoring the individual machine differences, is "width per bite, aka slice thickness. One balance RPM vs feed rate to keep the slice thickness constant.
Any chatter/vibration/jagged motion will affect slice thickness and is therefore unwanted.
Have you confirmed that your movements in the X, Y, and Z directions match what they should be? If the Z scale is wrong you could be carving to deep. You should be able to check this by telling each axis to move an inch and measure how far each moves. Also if you have one of your failed pieces, measure how deep the end mill cut. You really should not be breaking bits cutting pine. I’ve cut much more aggressively through pine plywood with cheep single flute bits.
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