I thought that was the case with the old material, so I ordered new stock from Howard Precision Metals confirmed 6061-T651 (“confirmed”, I didn’t actually request a material cert).
From looking at the video some more, it really looks like the Z-axis carriage is rotating about the X-axis.This correlates with the fact that the chatter is worst when the machine is cutting only in the Y direction. It seems like the cutting force from the single flute tool is causing this rotation but the system stiffness is just in the wrong place and it wants to resonate.
What I’m not sure about is if this lack of stiffness is coming from the v-wheel design (probably not, others don’t seem to have this issue) or flex of the Z-axis carriage itself. I just don’t want to spend $300 on an upgraded Z-axis if it’s not going to fix the issue.
I will run some more tests with the recommended settings, but from what I’ve seen from others, the machine should be capable of higher material removal rates. Maybe those people are all using upgraded machines. I just want to make sure I understand what’s going on so I don’t just end up throwing money at the problem.