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If I cut a dado 2mm (1/16"+) bigger than a panel leaving space for movement, do I also need to leave 1mm of space on each side of the panel when inserting it or will the panel adjust itself?

This is for a shaker door in a cabinet where the styles and rails are made of 20mm maple and the panel is 9mm birch plywood. I was planning on making the dado 6mm deep.

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    What is the panel made of? Solid wood, or MDF, or plywood, or? Edit the question and make it as complete as possible so you attract a good answer. I simple drawing with dimensions will not go amiss, either.
    – jdv
    Mar 20 at 23:49
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    jdv is right, we need more information, not just the type of wood fitting in the dado, but the overall width of the panel. The amount of expansion depends upon the type of wood and other factors such as the orientation of the grain and the situation the project exists in. Furniture in a conditioned space does not expand and contract as in uncontrolled locations with greater temperature and humidity fluctuations. There are plenty of folk who can help here, but we need more information about the size and construction details to give meaningful responses. The more you share, the better.
    – Ashlar
    Mar 21 at 2:16
  • Yes you normally want to centre the panel. 2mm total would not normally be enough but as mentioned already the material of the panel is critical here. If using solid wood both the species and the cut are vital to knowing how much you should give; QS wood moves much less than flat-sawn. And obviously the dimensions too, since total movement is directly related to width (wider panels expand/contract more than narrower panels of the same material). But if using plywood or another manmade board material you may get away with a tight sliding fit; many drawer bottoms are fitted this way for example.
    – Graphus
    Mar 21 at 5:09
  • All that above, but the answer probably comes down to 'panel spacers'. (Google "spaceballs panel spacers" for one generally available brand.) They will center a loose panel and prevent rattling. Mar 21 at 14:28
  • Well since it's ply you can allow basically no extra space (so maybe 0.5mm clearance) and you can get away with it. Some woodworkers still do but for what I call 'personal voodoo' reason because like I say commercial drawer bottoms are often made to be a tight sliding fit and don't give any issues in the long term, and these are frequently wider than a floating panel in a typical cabinet door.
    – Graphus
    Mar 21 at 17:07
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There are specific situations where solid-wood wooden panels are installed to allow expansion and contraction to occur outwards from one edge. This is chiefly used for tabletops that will be positioned against a wall, like the classic demilune (see image in previous Answer to What general considerations do I need to take into account for wood movement?). While in principle this same thing could be adopted for a floating door panel the convention is to centre them.

However, since you're using plywood for your panels movement is basically a non-issue. Ply panels can, and often are, sized to be a tight sliding fit into the grooves of the frame (or box sides) that they are mounted in.

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  • Does one need to account for the fact that the frame into which the panel slides is solid wood and will move even though the panel won't?
    – FreeMan
    Aug 23 at 10:57
  • @FreeMan, do we account for aprons expanding enough to lift tabletops off? Same thing basically.
    – Graphus
    Aug 23 at 17:11

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