Hahaha!
Well this evening you start with? Newly mounted spindle, new feeds and speeds, what else?
I’m still leaning a little on that spoilerboard/mount thing. 4x4x3/4" MDF on the way home… 
Yeah, moved and reseated the spindle mounts. Going to try a run with GWizard prescribed speeds resulting in 0.0013" chipload.
I did raise the spoilboard so I think we’re good there. I basically just took a 4’x2’x3/4" MDF board and screwed it to the spoilboard I already had, that raised the work piece 3/4" closer to the axes and definitely helped. Will grab another full 4x4 sheet this weekend maybe.
10-4
So the saga continues.
This time I was at 0.5doc, 500mm feed, 19646rpm. This gives 0.001" chipload. Looks better but still that nasty chatter on the last pass and I am once again out of round.
From watching this one it sounded like there’s a little chatter on the stepover maybe so I am doing it again same settings but slower stepover feed rate.
So…reducing stepover feedrate helped a little, this started me thinking down a whole other path. What if its not just deflection on the bit, but what if the movement towards the wall is causing ringing when it stops?
My jerk settings on my TinyG G2 firmware were at 5000M mm/min^3 which is what they recommend for Shapeoko, and I’ve been using these settings for ages (as has @Brandon_Satterfield ) But at this point I thought I’d try anything.
Reducing jerk to 1000M mm/min^3 helped a bit, and finally reducing it down to 500M mm/min^3 has resulted in something passable I suppose.
More chatter on that final pass than I’d like, but its not throwing the entire hole massively out of round anymore, there’s a very slight deviation where the chatter is but its in the <0.5mm range now. And checkout the surface quality of the finished cut:
So, is it possible this is all just tool deflection? And the reduced jerk has hidden what is actually a badly deflecting system? Or is it actually ringing on that last move out to the wall?
In the end I asked the machine for a 28.45mm hole, and I got a 28mm hole dead on as far as I can tell, maybe a hair over. The 28mm bearing the hole is intended for fits perfectly with no interference and no detectable movement with the limited sensing abilities of my finger.
Ben I’m glad you have something off the machine.
There are three differences between your and my own machines.
Collet
Spoiler board
Controller
The above hints that it could be any of these.
As I said though, very happy to here you could get one off there.
Yeah, going to try and do a proper part tonight which involves some spiral cut holes for 5mm screws and an outside profile cut. I will try messing around with the max jerk settings a little more.
I think this might all be down to using G2, do we know if anyone else is using TinyG G2 for their CNC cutting aluminum?
Dumb question, but does your end mill have flutes for the full depth of your cut? Can’t tell from the video because it’s always spinning, but it does look shinier very close to the to top of your work.
Worth checking @Len_Sherman but yeah it does. It’s got way more than enough. I think it’s 14mm flute and I’m cutting only 1/4".
Just out of curiosity did you tram your z axis?
I did, but clearly not well enough I think. Since this post I’ve moved on a bit and through different machining methods have avoided this issue. But there’s definitely some mis-alignment of my z-axis as now when I face some aluminum I can feel and see the passes as ridges on the face of the stock. So the z is definitely mis-aligned somewhat and I’m going to have to work on that.
Another thing to consider is the type of bit that you are using as well. Do you get the same result using a conventional cutting method
Switching to conventional definitely helped. But it’s still there just much reduced. It’s an issue of deflection but only in a certain plane across the machine from +X+Y to -X-Y. I think it just be z acis misalignment to be honest.
Just a few more ideas that have also helped me, Use double stick tape to hold the sheet more securely along with your current hold down method and chuck up on the bit as much as you can to reduce the how much of the cutter is protruding from spindle.
never mind. I just saw