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CNC for MDF cabinet panels

Discussion in 'd.i.y.' started by Adam N, May 18, 2020.

  1. orangeart

    orangeart KJF Audio Ltd.

    The clearance of .25 is fine. The main problem you have though is that your stock isn't a uniform size and this presents 2 problems with your rabbet joint. First and most obvious is the width of your rabbet, you may specify it 18.25mm wide to accept 18mm MDF, but that MDF might well be 17 or 19mm. You'll not get the CNC place to compensate for that. The second and less obvious is that the CNC place will need to set a reference height for cutting, that will either be the top face of the board or the bed of the machine. You might ask them to cut a rabbet half the depth of the MDF sheet for maximum glue area. If they measure 9mm up from the base and the MDF is only 17mm deep, the inside of your box is smaller. If they measure up 18mm from the base (assuming 18mm thick stock) the rabbet will end up being 8mm deep not 9 mm deep and so your board with .25mm tolerance will now be 2mm to wide to fit in your aperture...
    Adam N likes this.
  2. JimmyB

    JimmyB pfm Member

    That much? I hadn't realised there could be that range in thicknesses of standard MDF. Maybe worth using Medite Premier as it has a thickness tolerance of 0.2mm @ 12-18mm.
    misterdog likes this.
  3. orangeart

    orangeart KJF Audio Ltd.

    MDF and stuff like Valchromat tend to be a bit better, but you only need a little variation to throw off the construction process.
    Last edited: May 21, 2020
    misterdog likes this.
  4. misterdog

    misterdog Not the canine kind

    Stored in a high humidity warehouse for example, I bought some '6' mm MR MDF once and it measured 6.8 mm.

    The wonder of wood.

    I have 2 Altendorf sliding table saws, the beds are steel/cast iron and the sliding tables and fences are alloy. In order to cut to 0.2mm accuracy you need to re-calibrate every month because the different metals expand/contract at different rates.
    orangeart and JimmyB like this.

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