TLDR: The pass from X min to max is lower than the pass from X max to min. This is creating very consistent ridges. Mostly prevelant in the center of the sheet.
I’m surfacing my MDF with a 1/2" Dovetail with a 1mm DOC at it’s deepest point( the mdf is old and not very flat). It’s cutting good with no chatter or skipping steps. It is cutting higher in one X direction than the other.
Have you checked the core bearing tension?
This looks to me like the core can tilt a bit.
I’ll check. I didn’t feel any movement last week in it but I’ll check again. Thanks 
Do you think the lifting only in one direction could be related to climb vs conventional milling?
Sure could be.
So if the bearings arent makjng good contact, the core would be shifting in both directions.
When doing conventional milling, the teeth of the bit rotate to pull the core closer to the beam. Because the router isn’t centered on the beam, this will pull the bit downwards.
Climb milling, the other way, will pull the bit further from the beam, and because of the offset of the router this will lift the tool higher.
This sort of is related to tramming, because the ideal position for the router is not where it will naturally sit when it can move like this.
I checked this morning and there is a very small amount of play… I’m going to tighten it and run another pass. Thank you.
This fixed it. I’m quite embarrassed to say that NONE of the 4 tensioning bolts were tightened at all. I’m amazed I was able to get some cuts in at all!
That’s actyally good. Too loose and the machine works. Too tight and the core cracks. It should only be 2 bolts to tension, and they should only be tight enough for all of the bearings to touch the rails.
