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Thread: Miter Fold bit selection/recommendations

  1. #1
    Join Date
    Dec 2011
    Location
    Rapid City, SD
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    623

    Default Miter Fold bit selection/recommendations

    Chemetal / Pure Freeform aluminum laminates are spec'd on an upcoming project. The Pure Freeform is only available pre-laminated to 3/4 MDF, so only option is miter fold method for edge treatment.

    Thanks to all previous posts regarding this technique, but have a few
    remaining questions:

    - Anyone else already experienced with these materials and this method?
    - Source/size of bit
    - True 90 degree bit, or do you agree with the 91 for glue line thickness allowance that i'm reading about elsewhere?

    Thanks!

    Jeff

  2. #2
    Join Date
    Dec 2011
    Location
    Rapid City, SD
    Posts
    623

    Default

    Okay, now that project is done, I've learned the miter method is likely best to avoid. I got lucky in regards to material - was able to use raw laminate, not laid up on MDF as originally spec'd. As project evolved, here's what I've learned:

    1- Previous work in the building had been mitered - possibly cut on panel saw, but more likely miter-folded. Aluminum edge is filed off at the seam to expose the bright aluminum, while the face remains painted. This gives a nice, sharp looking detail to the item, but miters all have some level of visibility/openness to the seam.
    2- Based on layering process this item needed, it was terribly difficult to predict exactly the right size to pre-cut material on the CNC, due to variables of laminate thickness, plus glueline x 4.... At close to $500 a sheet with shipping and 10-14 days to arrival, mistakes are simply not affordable. Again, as observed in previous work, many open miters were visible, and client was aware and nonplussed with the rough look.
    3- I achieved a much tighter, cleaner look by applying last layups after fitting/flush trimming substrate to adjacent faces in the more traditional method of laminating.
    4- If you attempt such a project, you may use a file made for laminates to dress the edges. However, even brand new laminate file had a tendency to chatter with a zipper sound, leaving a series of witness lines accordingly. Not real good looking, so I recommend a block of wood with 120-150 grit sandpaper adhered. Leveled out the chatter and left a really nice brushed aluminum edge.

    Important note: Some of the panels installed by contractor were located in an area of trapped heat behind the panels (30-40 feet in the air, no less!). Shrinkage of the substrate caused straight line bulges where the aluminum was arching up off the substrate - like 1/4" of lift.( Aluminum and wood do not move at the same rate -who would have guessed, the architect who spec'd this material???). As a local fellow tradesman commented regarding working with all this fuss in trimming/filing/brushing: "I would rather have toothpicks shoved under my toenails than do another metal laminate job"
    I agree to an extent, but if you're able to exert the patience required, this is a very sharp, modern look. However, it is not for the faint of heart or someone looking for a quick buck.

    I'm really looking forward to my next project, where I can be a woodworker again. Hot aluminum shavings stinging my skin just is not a lot of fun, and a hell of a mess to clean up.

    Jeff

  3. #3
    Join Date
    Mar 2004
    Location
    Delray Beach, FL
    Posts
    3,630

    Default

    Miter fold machines have not only precisely machined beds but also really precise z adjustment.
    You can actually pull this off on a shop bot but you need to:
    1. run your surfacing routine first to insure your spoilboard is dead flat to you your gantry.
    2. Make sure the bit is a true 90-Note some miterfold bits are slightly over 90 for sufficient adhesive, but if yours is one of those make sure you use your machinist square when folding for dead on accuracy.
    3. Your part has to be completely in contact with your spoilboard. Any warp at all and you are dead.
    Then it can work, but it still isn't really the right machine for doing it on a regular basis.
    Frankly, I always did it on a table saw in my own shop, but again, there are some "tricks" that make it work and if you don't use them your joins will be a failure.

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