I’m new to woodworking and was wondering about the best way to cut dados in MDF. I’ve seen tutorials on cutting dados in real wood using chisels, but I don’t know if it applies to MDF as well because I’ve heard MDF is much more flaky/crumbly than actual wood. I have access to a circular saw, which I was told by a friend I could use to cut them iteratively, but that just sounds like a pain in the rear. I don’t have any planes, and the only electric tools I have are the circular saw and my power drill. Is there a good way to do this without having to purchase other tools?

  • A router with a pattern bit is your best bet. Feb 23 '18 at 20:19
  • 1
    "sounds like a pain in the rear" Many things in woodworking take longer than you want or expect, especially if being done correctly. Adjusting your expectations early on about the time and effort something 'should' take will prepare you well for any future woodworking endeavors. FWIW everyone starts out thinking things will take X amount of time and finds out slowly, iteratively if you will, that in reality it takes XX or XXX time instead :-)
    – Graphus
    Feb 24 '18 at 12:36
  • You have revealed only your power tool line up. This includes a circular saw which is on the short list of the most commonly used tools to cut dados. However, it sound's as though you may be averse to it's use in this application. If so, in order to know whether other options might be available to you without purchasing more tools, we would need to know what, if any, non-electric tools you have at your disposal. Also, Graphus' comment is good wisdom.
    – Otto
    Feb 27 '18 at 7:50
  • @Graphus, thanks; this is good to know. I'm ok with taking the necessary time, I just wasn't sure if there was a better way to go about it under my constraints.
    – KSchank
    Feb 28 '18 at 22:27
  • @Otto, in addition to my circular saw and power drill, I have a mini hacksaw, a hand saw, and some cheap chisels that I haven't ever used yet (but no cash for a sharpening stone), so my options are pretty limited.
    – KSchank
    Feb 28 '18 at 22:28

MDF is worked with the same tools, but it will be characteristically flaky, as you say, and it will tend to dull edges faster. It's not clear what hand tools you have exactly, but I am guessing you have chisels? If have only chisels and circular saw (power drill isn't very useful here), here's what I would do with your setup:

  1. lay out the dado. scribe the lines with a marking knife to assure a clean appearance.

  2. rough in the joint using the circular saw. Stay ~ 1mm away from your layout lines, but use the depth control to sneak up on the exact depth.

  3. finish the joint using chisels.

  • This technique works well in wood as well, and with MDF being so soft chiseling the waste is easy. The biggest concern is defining the edges, due to MDF's tendency to chip and flake.
    – Eli Iser
    Feb 20 '18 at 15:37
  • I just put this method to the test and it worked well. A few taps on the chisel created an outline. Then I hammered the chisel hard a few times in each section until it broke free.
    – ChrisB
    Aug 28 '20 at 3:15

To add on to @aaron's answer. A router plane, dado plane or rabbet plane will work fine in mdf. I would score a deep line if your tool does not have a knicker when starting. I would also take small bites. You will end up sharpening more.

  • As I mentioned, I don’t have any planes.
    – KSchank
    Feb 21 '18 at 19:42
  • 2
    look up Paul Sellers' "poor mans rabbet plane" - he makes a rabbet plane out of a chisel and a block of wood. Ditto for "poor man's router plane."
    – aaron
    Feb 22 '18 at 12:36

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