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Thread: Downspirals for MDF

  1. #1
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    Downspirals for MDF

    I am not a fan of downspirals for basically anything (though we run compressions so sort of) but we have a bunch of MDF (devils wood) to run in the future and I am trying to get as close to a flawless finished surface off the machine as possible. No fuzzies on the edges, little to no sanding required before primer. I dont mind taking and RO and knocking down the top surface before it comes off the machine which is what weve been doing. Virtually anything you seem to find and a couple of tooling suppliers have stated that a downspiral will give the best results. I only have a few 1/2" solid carbide down spirals and havent loaded one up to try (we will be running either 3/8" or 1/4" for this work). Even with smalll diameter compressions in MDF we dont have any luck clearing the cut (packs in pretty tight) but I was hoping to avoid the compression and having to cut so far into the spoil board. Have been running straight 2 flutes but still a bit of cleanup.

    What tooling have you found to give you the cleanest possible finish on MDF (top surface, bottom surface, and as little fuzz as possible).

    Even though we could single pass I was wondering if multi-passing 1/2" and 3/4" MDF would help clear the chips as well as clean the cut. Hoping to minimize testing/trying different setups a bit.

    Thanks.
    Sometimes I just want to look at pretty pictures,... Thats when I go to the Turners Forum

  2. #2
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    What tooling have you found to give you the cleanest possible finish on MDF (top surface, bottom surface, and as little fuzz as possible).
    It seems to me that a compression cutter remains the best choice for the job based on your requirements. It's the only one that's going to give you the best edge on both top and bottom. A down-spiral will provide an excellent top surface, but not so when you break through the bottom. The compression bit is up-spiral on the bottom and down-spiral on the rest. The compression bit will also be less prone to burning at the bottom than a pure down-spiral will be. Down-spirals bring greater risk of ignition.

    My understanding is that it's best to dedicate the cutter(s) to the MDF, however, because of the nature of the material and what it does to tooling edges.
    Last edited by Jim Becker; 07-01-2018 at 1:24 PM.
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  3. #3
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    Quote Originally Posted by Jim Becker View Post
    It seems to me that a compression cutter remains the best choice for the job based on your requirements. It's the only one that's going to give you the best edge on both top and bottom. A down-spiral will provide an excellent top surface, but not so when you break through the bottom. The compression bit is up-spiral on the bottom and down-spiral on the rest. The compression bit will also be less prone to burning at the bottom than a pure down-spiral will be. Down-spirals bring greater risk of ignition.

    My understanding is that it's best to dedicate the cutter(s) to the MDF, however, because of the nature of the material and what it does to tooling edges.
    Yeah, we do relegate cutters to MDF as they will never perform well in solids or ply once they have come in contact with the devil spawn. One issue we have with compression's, and why I was trying to avoid them, is they can very quickly tend to form an ever so slight ridge in the cut where the up/down shear meet. Its super small and is never an issue in ply or material that is going to be edge banded. But when your running MDF that is going to be edge finished that slight ridge is a nuisance if it has to be dealt with (which is impossible in intricate profiles). This was what was behind my considering a single shear or straight profile.

    The ignition issue in the bottom of the cut doesnt bother me as we never leave the parts sitting or the DC full after working with the evilest of materials. If it wants to combust outside so be it.

    Thanks Jim.
    Sometimes I just want to look at pretty pictures,... Thats when I go to the Turners Forum

  4. #4
    Can you use a continuous air blast at moderate pressure pointed at the bottom of the bit to clear the channel as it is cut? Just a copper line will likely do the trick unless you already have piping in place for that purpose. If it can be very close to the bit and pointed down at the channel at sufficient pressure to clear the channel and yet stay inside the dust shoe then that will likely do the trick for whichever bit you choose.

    David
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  5. #5
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    How about running a downcut bit on the top surface and coming back with a upcut for the majority of the thickness? You might have to run the second bit a couple thousandths in from the first to avoid a step, but I am guessing that would not fuzz up the top surface too badly. Otherwise a compression bit and whatever cleanup is necessary. Could you run the compression bit again at a different height to eliminate the ridge?

  6. #6
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    I've always cut MDF with compression spirals. I've had hundreds of customers over the years do all their MDF cutting for edge banded pieces with compression cutters. I don't remember anyone having an issue the edge quality (that was bit related, anyway).

  7. #7
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    Mick, The issues isnt with pieces being edge banded. Those are gravy. But these parts are going to be finished and painted. So the slight ridge on the edge from the compression shows. These parts are fairly intricate so are not easily sanded (if all has to basically be done by hand one at a time).

    The two cut method is one I have played with but may of the parts are thin and will not respond well to a second cut.

    We have an AUX air line run to the spindle that I use for a mister when we cut aluminum (with a noga mini cool). I use it often with just a lockline air line pointing at the cutter to clear chips. Oddly this is one of the rare situations where leaving the cut full of chips helps with support and vac.

    Thanks so much for all the input.
    Sometimes I just want to look at pretty pictures,... Thats when I go to the Turners Forum

  8. #8
    I like single flute carbide for speed. Especially the narrow less balanced type.

  9. #9
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    Quote Originally Posted by Mel Fulks View Post
    I like single flute carbide for speed. Especially the narrow less balanced type.
    Mel, not sure if your being witty or do you mean a solid carbide o flute singe edge cutter? I have never looked at the CEL but that may actually be an option.

  10. #10
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    Mark...
    Look at single flute compression bits
    Gary Campbell
    CNC Technology & Training

  11. #11
    Not sure of the proper term. But some of the single flute bits have a lot more metal than others, I'm guessing that is for balance. That type cuts slower than the the leaner type which can be out of balance after a sharpening.

  12. #12
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    Have you considered cutting in a two-pass operation? I think you have a MultiCam with ATC, right? Compression followed by a downspiral?

  13. #13
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    Thanks for all the input. Ordered some different tooling this morning. And Mick, yes, I'm thinking a roughing pass leaving a few thou for a light finish pass and onion skin followed by cleanup pass and a final to cut the skin would be the flawless route.

    At that point I'll have to decide whether a different material may be better.

  14. #14
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    Look into Plum Creek MDF it gives better finish on cuts. We use that for projects that require a good edge that needs painting

  15. #15
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    So will any of the above suggestions work for plywood or veneer as well? I am tooling up for my new Saturn 2 4x4 machine with a 2.25 Hp router motor.
    Retired Guy- Central Iowa. , LightObject 40w CO2 Laser and Chiller, MakerGear M2 3D Printer. Fine Line Automation 4x4 CNC Router- Mach4 ESS

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