I was trying to make some dados for a shelf for the first time and unfortunately, they did not come out perfect. The dados on the left and right side are unaligned, about 0.5-1.5mm (~1/32").

The depth of the dado is 9mm (half the material) and not super tight. I have never done this before so I am uncertain. Can I continue gluing up the carcass and inserting the shelves later? If I manage to insert the shelves I understand they will not be leveled, but I am fine with that

Dado1 Dado2 Dado3

  • 0.5mm total error is probably too small to see, while 1.5mm will be noticeable, but if you're fine with the shelves not being level then I don't think this is a big deal (although you can fix this if you would prefer). If the individual shelves are already cut their original length will be slightly off because of the diagonal, but you should still be able to get them in. Do a dry fit and check this first, trim a fraction off if necessary. BTW do you know what mistake was made that resulted in the mismatch, so you can avoid it in future?
    – Graphus
    May 17 at 16:07

This is your project, so in the end, it is your call. You have a few options:

  1. Do nothing! Try a test fit and see it if looks ok. If so, move on to the next step! Generally speaking, a 2 mm difference over half a meter/a few feet will not jump out at the viewer (unless there are other errors). Nor will it compromise the structure of a bookcase (a forgiving design).

  2. Do almost nothing. You can insert thin shims under the shelves (on the side with the larger dado). Again try a test fit - it will work but you may not like the look.

  3. Recut the smaller dado - make sure you pick the correct side of the dado to cut! You want dados at the same height and size to avoid shelves with a slight diagonal across the case.

  4. Use a hand tool to trim the small dado - depending on your hand skills and hand tools this can be quickly cleaned up with chisels or special hand planes. Again, you want to cut the correct side of the dado - the shelf should install with right angles to both sides of the case.

I would advise against trimming the shelf to match the two different dados but you can make that work as well.

Ensure that the shelves are secure when assembled - that is important. :)

  • 2
    Good summary of most of the options! For any grooves that need it instead of wedges I was going to suggest slips of cardboard as packing material, although fitting it could be tricky it'll be invisible or barely noticeably in service.
    – Graphus
    May 17 at 18:57
  • I should have said shims instead of wedges. I’ve seen veneer used to correct similar issues.
    – ewm
    May 17 at 20:43
  • 3
    @ewm this is why you can edit your answer. Always go back and improve answers. The idea is to grow good Q&A.
    – jdv
    May 17 at 21:27

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