I am boring a small (4.5mm) hole with a 1/8" bit on an Altmill. My original plunge rate was 1400 mm/min which caused the entire mill to shake rather violently. I dropped it down to 700 mm/min and while it reduced the amount of shaking, it still seems excessive to me.
Is there anything I can do to reduce shaking (short of bolting the mill to the wall)?
@Jens What toolpath are you using to bore the holes. On my LM, I use a profile tool path with a spiral ramp. I do them with a feed rate much faster than your settings - depending on the material, somewhere around 2000 mm/min, with a small pass depth.
I am using fusion with a boring tool path which uses a spiral ramp. I will have to double check but the default ramp angle is 2 degrees which, as I am contemplating this, causes quite a few ‘revolutions’. I think I will play with the angle and possibly the maximum step-down. Maybe that can tame things a bit. I will have to look at my feed speeds again.
The entire Altmill moves probably 1/2 inch and at a rather frightening speed but the holes are perfectly fine.
I like to go at rather conservative speeds for small bits as I have a nasty habit of breaking endmills (this was when I was cutting steel on a knee mill)
@Jens My apologies, Jens, for writing with the context of VCarvePro.
LIke you, I go conservative with 1/8" end mills.
I don’t think it makes a difference what cam program is used, it’s a matter of physics and throwing around a heavy object (the spindle/router).
I just ran another (air) test with a ramp angle of 20 degrees (vs 2 degrees). There are now 6 rotations in the spiral as the mill is fed in vs probably a hundred. It solved my issue.
Funny thing is that the counterbore, done with a 1/4" endmill had no issues even with the default 2 degree ramp. I suspect it’s because the circular path is very tight with the small endmill with less than 1.2 mm between the tool diameter and the hole diameter.
Thanks!
@Jens I completely agree. My point was only that, not knowing that CAM application you use, I could not know if a spiral ramp was even possible.
Ah, sorry I wasn’t clear in my original post.
@Jens No apology required. 
The important thing is that you are squared away now.
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