8/4 Stock flip milling

I am looking to carve out a piece from some 8/4 maple so I know I will have to carve out the shape on one side, then flip the stock over and carve out the same shape flipped horizontally.

Although this was only the first time I tried it, I was very cautious to place the material in the same exact spot once flipped, ensured the artwork was centered before and after flipping horizontal in Easel and I was fairly certain the same xy start position was on the lower left corner for both sides.

However, it still needed up being pretty off when I looked at either the shape carved out or the remaining stock (picture below).

I may need to watch the 30 min Inventables video I believe I saw, but I also saw this post below speaking of doweling - how would that work?


Without an exact reference is almost impossible to get a perfect match. One degree off will snowball to a bad result. Just add holes and then mirror them for the other side

Let me ask a rookie question here…how would the hole process work? Are these drilled separately or CNC cut out? I’m thinking the latter is problematic on 8/4 stock where I can cut all the way through without flipping and thereby creating the same problem. And once you have the holes, what do you use to make them attach to the wasteboard or something else for reference when you flip?


  • Home the machine (sync machine with model enviroment
  • Set your work zero
  • Carve two holes in the wasteboard, center aligned with your part (no stock in place)
  • Carve seperate, matching holes on your stock part (partial hole is fine)
  • Flip stock, use dowels to align stock with alignement holes
  • Carve two new holes (for later when you flip again to face 2nd side)
  • Carve 1st face
  • Flip material, align using dowels
  • Carve 2nd face

Outstanding, thank you! Somehow I just couldn’t put all the steps together in my head so this is perfect!!!

Having not done this, I’m having trouble visualizing this and just want to make sure of two things on this technique:

  1. For step 3 where you carve the two holes in the wasteboard, does this need to be done in the same session, meaning do I need to do all of these bullets without stopping? Or if I do step 3 for the wasteboard holes once, can I re-use these holes every time I do this same job, even if I have done other jobs with other work zeros in between?

  2. Overall, when doing this technique, it’s not critical for the work zero to be absolutely in the perfect lower left of the stock because the dowels control the precision, right?


1 - This need to be done using the same reference system, aka machine homing. I home the machine, set a work zero and carve the reference holes into the carve surface/board. Then I insert my blank over these holes and carve the same holes on the blank itself after re-zero of Z only. Then turn the blank over, using dowels and carve holes for the 3rd time. You now have a blank with aligned and matching reference holes for both sides :slight_smile:

2 - The above method do assume the blank is slightly oversized. If you have a fixed blank size to work with I´d simply carve a slight recess to align your blank. If its oversized it is not critical.

All sounds good. So for #1, it sounds like all of these steps need to be done sequentially in that “job”, meaning that if another day we want to do this job again (and we’ve done a new work zero for another job), then we’d have to do all of these steps all the way through.

In doing so, this probably creates a lot of holes in my wasteboard, making it eventually look like swiss cheese, is that a problem? Or I guess each time we should be mindful and move the stock around so that the next set of holes doesn’t conflict with the side of an existing hole (thereby making a misshaped hole that doesn’t hold a dowel).

I often will put a sacrificial board between my stock and wasteboard to account for this, but with 8/4 stock, I can barely get the stock under the carriage, so I know I wouldn’t be able to get a sacrificial board under there that would hold a dowel.


Yeah, those holes will be “job specific” and I see the stock vs available height issues.

What one can do, if this will be a typical workflow for “you” then perhaps a pilot hole grid could be implemented, references off machine home. The accuracy will be determined by the accuracy of the machine and switches.

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