When and what to flatten

So i looked and didnt really find my answer so i’m going to just post this question.

ive had the shapeoko for almost 6 months and once i put it together i never did any sort of flattening, just set it up and ran with it. in the beginning (as i was learning) i made some mistakes and put some mild grooves in the hybrid table MDF of my Pro XL.

in some of my projects (usually pine) i can see a cut depth difference along the Y axis (front to back). this may be due to the pine but i would imagine i want a perfectly flat surface to start with.

i went and bought a fancy Whiteside 6210 CNC Spoilboard Surfacing Router Bit, 1/4" Shank so my question is…do i flatten the hybrid table or just keep flattening sacrificial boards on top of it.

sorry if this has been answered already but i couldnt find it
thanks gang

Opinions vary here’s mine. I surfaced my hybrid spoil board and always zero to the machine bed
This eliminated cutting into it unless I do something stupid. I will also surface stock unless I am positive it is of uniform thickness. Surface super thin since you may need to tram and probably surface again. Truthfully either strategy works and you can do both

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ok i think a light bulb just went off.

originally i read to zero to the bottom of the project piece and then i read to zero to the top. am i “correct” in thinking to zero to the bottom if i want to cut all the way through but to zero the top if i’m just doing engraving?

i guess, is there a downside to zeroing to the bottom if i now have a perfectly flat bed?

I don’t think that there is a downside to zero at machine bed

Key to engraving is a surfaced and trammed machine and consistent stock thickness. A perfect carve will require both. A 3d relief carve should take off a consistent couple of thousanths off the top but you don’t have that in a simple engraving… but your surfacing cutters can do it as well

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so im standing in front of my machine and planning to flatten the spoilboard. because the router will only travel a certain distance on the x/y and not the entire way is this a mistake? what if i have a large piece that spans the “flattened” area and the non-flattened area?
am i better off removing the mdf and running them all through the planer instead?

just trying to keep from making a huge mistake and causing more issues

Yes, the typical way to flatten will result in a pocket because as you note, the machine can’t reach the entire surface of all of the hybrid filler strips — if you wish to use stock larger than that, it is a problem.

The alternate way to handle this is to flatten the entire surface by removing and flipping the hybrid filler strips, flattening them, and then swapping them back.

Josh Tenny put a fair bit of effort into this:

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so with regards to tramming, i think i get it but i want to be sure thats where my issue is. i put together a quick tramming tool and here is what i see…its clearly nothing fancy and definitely not perpendicular but not sure it matters

wanted to post these before i started taking things apart. history shows that can tend to make things worse
feels like it is tilting to the front right

facing the machine.

12 oclock position

3 oclock position

6 oclock position

9 oclock position