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Thread: Blind Dadoes

  1. #1
    Join Date
    Oct 2006
    Location
    Ottawa, Ontario
    Posts
    189

    Default Blind Dadoes

    I am considering taking the plunge and moving away from plane old butt joints for a few reasons now that may familiarirty with E-cabinets is on the rise (thanks to the videos everyone has been nudging me to take advanatage of)

    My primary box material is 16 mm thick partical core Melamine . Initially my primary reason for going to this joinery is to get the registration offered by an interlocking joint AND to give me a means to identify better through assermbly marks orientation of key parts so I don't end up with parts upside down


    My questions are:

    - is 16mm too thin to use this construction
    - what percentage of the material should be used for the tenon and what depth and tenon clearance is a good number to start out with . I use 1//4" compression from centurion at the moment .
    - If I move up to a 3/8" cutter will my material be too weak at the joint to use this joint ?

    I have only applied the joint to the deck where it meets the sides in a base cabinet .When the Cabinet Editior draws this joint it would appear one tenon is 'transparent' and the other is 'filled in' ... Should this be a concern ? In the nesting drawings it appears the parts cut properly .

    Thansk Bill

  2. #2
    Join Date
    Jan 2006
    Location
    Un-Employed Westminster, Ca
    Posts
    578

    Default

    Tenon construction will work with 16mm material.
    I would use 50% for the tenon size and 8mm the depth. You will have to test on your machine but you could start with .020 clearance.
    You will have to use a 1/4" bit.

    What you are seeing on the screen may be your computer not rendering everything due to memory or processor speed. I would not worry about it.

  3. #3
    Join Date
    Apr 2007
    Location
    Marquette, MI
    Posts
    3,388

    Default

    Bill...
    Echo what Roger says. No reason not to use the tenon dado joinery. We use this almost 100% in 18mm material. We also have been using the assembly marks, especially for our flat pack wholesale jobs and the customers love it.

    To answer your questions:

    16mm is not too thin

    You will need to select a % that allows use of the 3/8 bit. The minimum would be 58% (.3653) plus .010 side clearance allows a 3/8 bit to machine the dado. You dado depth minimum would need to be .375 to match the bit. (or .355 with .020 depth clearance)

    I would use a 1/4" bit for 1/2" material, but really prefer the 3/8. I feel it allows much faster cutting and the evacuate chips much better. They last longer and there are many more options, like chipbreakers for the 3/8.

    I am not sure how partical board will hold up on the panel end between the blind dado and the end of the part. You will have to test to see if your material holds up.

    I agree with Roger on the rendering, if the parts cut good, they are good!

    Gary

  4. #4
    Join Date
    Oct 2007
    Location
    Ernest Klassen Kitchens, Fenwick Ontario
    Posts
    116

    Default

    I've been building cabinets with 5/8" (16mm) particle core melamine and blind datto construction since May of last year. Made the switch when the link first came out. I use 40% tenon size and 1/4" depth which with the 5/8" melamine works out to be 1/4" x 1/4". I use a 1/4" compression spiral bit for all datto and outline cuts. A 3/8" cutter won't leave enough strength in the 5/8 melamine and cuts slower on a non-alpha machine. I use a melamine glue for assembly. One thing I'm still trying to improve is that the particle board gets rather ragged on the tennons, probably because I'm not using a mortise end compression bit.

  5. #5
    Join Date
    Jan 2006
    Location
    Un-Employed Westminster, Ca
    Posts
    578

    Default

    Bill,

    Something I forgot to add is that on mid-shelves I always use 100% thick tenons. I have not used assembly marks. But with 100% thick mid-shelves assembly is fool proof. You can't put it together wrong.
    I have used several people assemble my cabinets with only about 10min training.

  6. #6
    Join Date
    Oct 2006
    Location
    Ottawa, Ontario
    Posts
    189

    Default

    Thanks everyone for the input . I tried a few test this evening and found a good fit with .007" side clearance but I saw something that concerns me a bit . I am using a 1/4" bit (all I have at the moment) with a 1/4 X 1/4 tenon . I do a two pass cutting strategy with the onion skin coming off in the last pass . However that last pass goes out around the tenon so that it does not clean up the shoulder of the tenon and there is a small 'bump' on the shoulder where the tenor begins . Should this be a concern and is there a way to solve it other than a 3 pass cut of some sort (the link only supports 2 pass' I think) .

    If I use Melamine glue in the joint will it fill in any possible gap caused by the above .

    Thanks Bill

  7. #7
    Join Date
    Jan 2006
    Location
    Un-Employed Westminster, Ca
    Posts
    578

    Default

    Bill,

    A picture is worth a thousand words.

  8. #8
    Join Date
    Oct 2006
    Location
    Ottawa, Ontario
    Posts
    189

    Default

    This is it . The bump is in the top surface .
    50363.jpg

  9. #9
    Join Date
    Apr 2007
    Location
    Marquette, MI
    Posts
    3,388

    Default

    BIll...

    There are differences in the paths of the bit from your tenon dado cuts and your perimeter cuts. 3 things cause this:

    1) Improper bit size. Mic to confirm

    2) Deflection, either machine or bit. Use larger bit, sharper bit, more aggresive bit or slow down cut speed should cure the bit portion.
    Make sure all V rollers in X, Y and Z are snugged up, along with pinions to the racks.

    3) Cutting directions:
    How do you have your 2 pass ouline cutting setup? Have you tried for your perimeter settings:
    Direction: Climb
    Check: "run all through cuts last" AND "Run opposite direction"

    For Rout Dado: check conventional

    Keep us posted
    Gary

  10. #10
    Join Date
    Oct 2007
    Location
    Ernest Klassen Kitchens, Fenwick Ontario
    Posts
    116

    Default

    I've had that problem before too. The 2 pass outline cutting strategy as Gary has explained above helped reduce it. Judging by 0.007 side clearance I'm thinking your V rollers need to be tightened up. When you do, you'll likely need to adjust your side clearance higher maybe 0.015" - 0.020"

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