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Thread: Looking for tip

  1. #1
    Join Date
    Dec 2007
    Location
    Sarnia, Ontario, Canada
    Posts
    44

    Looking for tip

    Okay.. I just ruined some oak plywood while trying to cut a dado in it. I scribed the cut on both sides before cutting it, and I ran it through nice and slow.. and it still tore the vaneer off the plywood.. it splintered the edge badly.. what did I do wrong..??
    I am using 3/4" oak plywood, and cutting a dado 3/4" wide, by 3/8 deep. with a Freud dado set.. the set is new.. maybe a dozen cuts on half the blades..??

    Could it be old stock plywood maybe.. or maybe I never scored it deep enough.. or maybe it was the loose nut behind the saw..

    Ruined my sheet anyway.. at $80.00 a sheet.. I don't want to do that to often..

    Any ideas would be appreciated ..

    Doug
    Master creator of precision sawdust and slivers.

  2. #2
    Join Date
    Dec 2006
    Location
    Somerton Az
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    4
    On the piece that is ruined try putting masking tape anywhere you want to cut your dado. Reed Kempton

  3. #3
    Join Date
    Apr 2007
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    No, not all of SoCal is Los Angeles!
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    9,076
    Ouch, that hurts. Well, now that you have some material to test on; I am assuming crosscut. You say you scribed each side, here you mean you cut it with a razor knife, not just a marking knife, yes? Some folks have better luck with tape over the cut area and cutting the veneer but I generally don't do either.

    Is this a 200 or a 500 series Freud? The 200 series is supposed to do a pretty good job and my SD508 leaves a very respectable edge crosscutting without other efforts as long as the feed is true. That being said, red oak is probably the most prone to tearing after ash. Razor cuts all the way through the veneer (about 1/32") should eliminate the tearing as long as the dado set is walking the same lines that have been pre-cut with the razor knife.

    Being a crosscut makes me think the piece being fed is long and narrow. Are you using a sled to keep the material at a stable 90* to the blade. In my experience, even the most tricked out miter gauge will not do the job if the piece is too long left to right.

    I hope I have hit on something that may help and not just blathered along with a bunch of stuff you're already trying. ;-)
    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C. Clarke

  4. #4
    Join Date
    Mar 2007
    Location
    WNY, Buffalo Area
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    Doh! - I thought you talking about making the dado with a router. - My Mistake
    Doug,

    Are you trying to take all 3/8in in one pass? That might be the problem.
    Now that you have some scrap, try doing it in 1/8in deep passes.

    Another option would be to change bits. A down cut spiral will do a good job on plywoods and other veneer laminates (like melamine). This is because instead of cutting across like a standard straight bit, it cuts down tending to preserve the veneered surface.

    If you aren't familiar with them, spiral cut bits can get pricey. They generally come in either HSS or Carbide. The Carbide ones cost 2 to 3 times what a HSS costs, but have a much longer cutting life.

    Just my 2 cents.
    We create with our hands in wood what our mind sees in thought.
    Disclosure: Formerly was a part-time sales person & instructor at WoodCraft in Buffalo, NY.
    www.tinyurl.com/thewoodshoppe

  5. #5
    Join Date
    Dec 2007
    Location
    Sarnia, Ontario, Canada
    Posts
    44
    I scribed the lines each side of the dado cut with an exacto knife, and I might not have cut all the way throught the vaneer. I will try cutting a little deeper on the next sheet..

    Thanks guys.. much appreciated.

    Doug
    Master creator of precision sawdust and slivers.

  6. #6
    Join Date
    Dec 2006
    Location
    Charlotte, NC
    Posts
    1,487
    I use a piece of tape along the cut lines. Seems to help with tearout. I have also started using my router for dados instead of the TS. Nice, clean, accurate and I don't have to wrangle the sheet goods!

  7. #7
    Join Date
    Nov 2006
    Location
    Houston, Texas
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    Hi Doug ,
    I think Ed has a good idea on that cross cut at least. Using a router and a home made reuseable jig with a 3/4" cutting bit may save you time and money in the long run. That is if you have the router and the bit already.
    Shaz
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  8. #8
    Join Date
    May 2007
    Location
    Kansas City, Missouri
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    Quote Originally Posted by Ed Nelson View Post
    I have also started using my router for dados instead of the TS.
    I've started using the router as well. Bought some long guide clamps used with a set of boards for setting the off set from the line. I also have a jig for smaller boards (I think it was listed in Wood magazine recently) that one side moves and allows you to set the width based on the board fitting the dado. You then use a pattern bit with a top side guide bearing (1/2") to follow the jig when cutting the dados.
    Darren

    To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault

  9. #9
    Several thought came to mind when I read of your expensive Problem.

    I prefer to Score, either side of the Dado. Not just draw a line and gut the first layer but Tip the piece into the saw and allow the Dado to kiss the edge, back off shut down and then Use the saw's mark as the location indicator, as you may be just a "nanu" fraction off, enough for the edge of the teeth to skip past the scoring. Score from the tooth mark, not the measurement mark.

    Another thought is it may be the blade, yes you say you have a new expensive set, but I know for a fact that New does not mean perfect. They too may have a misplaced tooth, I have seen expensive blades "come from the box" with flaws, check that out...

    Another blade problem my be your set-up... If you swap the left or right blades, sometimes they cut differently, another problem may be the raker blades in the center must align with a space on the outer blades If the contact the teeth of the outer blades they can put out and cause a wide tooth creating your problem. And If you over tighten the set, you may bow out the blade making a couple of teeth strike wide of the joint, If you have some litter (dust, chips rust, grit, tape, price tag, etc. ) inside between the blades, or chippers, or shims you can create an aslew blade causing a few teeth outside the joint.

    Finally, It may infact be the material, Another poster, last week crabbed about poor quality ply from the BORG and all the delaminating problems he was having.


    There are several possible interests to look at to find your problem, Remember the use of tape to secure the edges is a good idea but it reduces the depth of the cut by the thickness of the tape, consider that. Blue/green painter's tape makes removal easier w/o leaving residue of regular masking tape. Package sealing tape will not effect the depth of the cut and can be removed easily if done soon after cutting. I sometimes lay down a strip of the2" tape covering the whole joint, cut through the center and peel off either side, right after the cut, But remember to pull toward the joint as pulling away from the joint may peel back the outer layer (Big Bad Oops!)

    My thoughts on the matter, FWIW

  10. #10
    Join Date
    Dec 2006
    Location
    Charlotte, NC
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    1,487
    Here's a quick step through my set up.

    1) screw or glue two 1/2" lengths of plywood together. One piece is narrow, but allows enough support for half of the router base. The lower piece is slightly wider than the distance from the OD of the router base to the OD of the router bit (I use a 1/2" pattern bit, although the bearing does not factor in). You will make two of these.


    2) Run the router along the jig with the base against the upper board and trim the lower board.



    3) Clamp one of the jig boards exactly along your dado line. using your shelf or whatever is going in the dado space to set the position for the second jig board and clamp that jig.


    4) run your router at the required depth around the jig.

    You now have a perfectly matched dado for the mating piece.

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