While I agree that tramming the spindle on a Shapeoko 3/4/Pro is not the easiest thing, you can still do it. I have trammed mine to within 0.002" over a 12" diameter using a spindle mounted indicator. Beyond tramming, here is what I have learned from my experience:
- Go slower.
Be sure to keep your chipload high enough for the tool you are using though. A balanced single flute is great for helping you to slow down while keeping chipload high enough.
- Keep tool engagement low and stable
Pretty straight forward. Your finishing pass should not be removing much material and sudden changes in tool load will show up in the finish.
- Use a balanced endmill.
Vibration caused by an unbalanced single flute is quite easy to see in a floor finish. It is one of the reasons I no longer use Amana single flutes. Go to a Datron 4 in 1 or a 2 or more flute.
- Keep endmill stickout as short as possible
The longer the stickout, the longer the moment arm on your tool, spindle and Z axis is. Keeping that whole stack as short as possible increases rigidity and decreases tool deflection therefore improving finishes. Raising your work as high as possible will help.
- Avoid sharp changes in direction.
Our machines are desktop grade machines and vibration from direction changes can be pretty significant depending on speed and acceleration.
- Reduce your acceleration values in GRBL (Optional)
I have reduced my acceleration values by 20% in my GRBL settings and found a decent improvement in finishes.