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Thread: Pocket Hole Joinery vs Dados

  1. #16
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    Quote Originally Posted by Bruce Benjamin View Post
    I won't question your ability to set up the dados in that time because, well, whatever. But even if you can do it in half that time you aren't taking into account the glue drying time that requires clamps. Pocket holes may or may not be slower but they save so much time overall because they require little or no clamping. How long do you have to keep your project clamped up before you can move onto the next step? I'll bet it's not faster than a pocket screw and glue joint.

    That being said, I don't want to use pocket screws where they are visible when it's anything other than for shop use. To me that's where the dados have a distinct advantage and worth the extra time spent.

    Bruce
    Morning Bruce..

    And you are correct about glue time. I did say pocket holes are fine for a router table. Frankly, I probably wouldn't even bother to use pocket holes. Just pre-drill a pilot hole and counter-sink for the screw head..run a narrow glue line.. align the stock and pop the screws in with a 1/2" drill with a phillips head bit. It's just a shop item that is used to produce "show items" as I see it.

    And I do agree with you totally that dadoes have a distinct advantage as in the example I mentioned with book-cases that will carry substantial weight. There is a lot of glue area in a dado not to mention the shoulder support on the opposite side of where the weight is placed.

    I can cut dadoes very quickly.. accurately and safely as I mentioned as I have created an advantage. I have a dedicated TS I modified and set up just for dadoes for up to 16" wide stock. I just have to line up the tick mark and slide them though. Just something I decided to do when I upgraded my TS I use for ripping and it it definitely has proved to be a time saver and safe approach to dadoes for me.

    Regards...

    Sarge..
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  2. #17
    I like PHJ's...the are quick, strong and no-brainers. Given there is a chance you might want to redesign a project you won't have the large dados in the boards when you use PHJ's....the opinion of a novice.

  3. #18
    Quote Originally Posted by Paul Comi View Post
    Stuff like this is what I bought the Festool Domino for. I'm not adverse to using pocket screws and even use them for making functional drawers sometimes since the slots for the screws get concealed by the applied drawer fronts, but I wouldn't rely on pocket screws for load bearing projects that would fail if the glue lost its bond. That's just me.

    If the casework you're building is plywood, the strength of your joinery using butt joints reinforced by pocket screws is coming mainly from the glue which can be substantial, but I like either rabbeted dado's or domino's or even biscuits or dowels to add some extra strength.

    If I was using butt joints to build that router table and didn't have the domino and also didn't want to install the stacked dado, I'd either use a router with an edge guide and cut rabbeted dados or regular dados or I'd pick up some Miller dowels. My .02
    I don't think you have it right regarding the strength of pocket hole screws. If you made two identical boxes made with butt joints and attached one using only glue and the other using only pocket hole screws, which one do you think would fail first if you jumped on it? The pocket holes screws are going to be stronger than the glue in a joint using a combination of the two but a combination of the two is even better. Glue in a shelf using only a butt joint and do one with pocket hole screws. Which one will you want to stand on? End grain doesn't glue very well whether you're using solid or plywood. Obviously, the pocket hole screws provide the majority of the strength in a glue/screw combination joint.

    I've never used Miller dowels but they're just made of wood, right? How are they stronger than steel screws? Since I've never used them I don't know what their strength is for shear strength or racking resistance. But I doubt that it's more than a steel pocket screw. Could be wrong though I suppose.

    Bruce

  4. #19
    Quote Originally Posted by John Thompson View Post
    Morning Bruce..

    And you are correct about glue time. I did say pocket holes are fine for a router table. Frankly, I probably wouldn't even bother to use pocket holes. Just pre-drill a pilot hole and counter-sink for the screw head..run a narrow glue line.. align the stock and pop the screws in with a 1/2" drill with a phillips head bit. It's just a shop item that is used to produce "show items" as I see it.

    I wasn't saying that I'd only use pocket holes on shop cabinets. I said I'd only use them on shop cabinets when they are going to be visible. They aren't always visible in furniture making.

    What's this, "Phillips head bit" you speak of??? I've never heard of such a thing? Are they new? Could you describe this whole process in more detail please?

    And I do agree with you totally that dadoes have a distinct advantage as in the example I mentioned with book-cases that will carry substantial weight. There is a lot of glue area in a dado not to mention the shoulder support on the opposite side of where the weight is placed.
    I don't see how you can agree with me on this because I never said or implied this at all. The only things I commented on was the visibility of pocket hole screws and the glue drying and the clamp time of a dado joint. I'm not saying I disagree with you. But I gave you nothing for you to agree with regarding the strength of the joints in my last reply to you. I don't think the dado/glue joint has a distinct advantage and I'm not sure that it's even stronger in every situation than a pocket hole screw/glue joint. A dado will probably be stronger for a shelf where the shelf isn't expected to control racking, (pushing straight down only) but I'm not convinced that a dado joint is stronger than a pocket/glue joint in every other situation. Where it is stronger I doubt that it has a, "Distinct advantage" with regards to strength and durability. One think is for certain, when a dado and glue joint fails it fails much more completely than when a pocket hole/glue joint fails. Once the glue or the wood surrounding the glue fails the joint is done. It takes more than that to rip the screw threads from their holes.

    There's still a lot I like about a dado and glue joint and I have used them a lot. But I'm not so quick to dismiss the pocket hole screw joint. To each their own. It's unlikely that either of us will be exchanging furniture anytime soon.

    Bruce

  5. #20
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    Quote Originally Posted by Gary Keedwell View Post
    To be honest, I've used both methods on the same projects.
    Gary K.
    Me too. Found it easier to use both.
    Making new friends on SMC each and every day

  6. #21
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    Evening Bruce...

    "I don't see how you can agree with me on this because I never said or implied this at all"..... Bruce

    I went back and re-read your post to clarify as I did mis-interpret it with the initial readind. Sorry.. my error!
    *****************
    "What's this, "Phillips head bit" you speak of??? I've never heard of such a thing? Are they new? Could you describe this whole process in more detail please"? .. Bruce

    Delighted to provide detail:...
    The Phillips screw drive has slightly rounded corners in the tool recess, and was designed so the driver will slip out, or cam out, under high torque to prevent over-tightening. The Phillips Screw Company was founded in Oregon in 1933 by Henry F. Phillips, who bought the design from J. P. Thompson. Phillips was unable to manufacture the design, so he passed the patent to the American Screw Company, who was the first to manufacture.

    I added a picture for visual at the bottom of a phillips head drive bit and a pilot bit with counter-sink. Hopefully that will cover the detail requested..?If not PM and I will send video.
    ***************
    And "I" do feel it has an advantage over just pocket screws when used singular. And of course it's an opinion. You mentioned using a dado when not used to control racking. If I designed something without a face-frame or no backing that assist in racking, I would probably use a dado and a pocket screw.

    I don't think I would rely on either singulary to be the main ingredient that countered rack with harsh conditions involved, especially on a large book-case (etc.) that was going to get subjected to heavy weight. Used together.. they would probably (depends) be sufficient, IMO.

    Of course, we could just use 16/4 stock and through tenons and then pin them with 3/8" lag screws. That would take all the doubt out..
    ****************

    "To each their own. It's unlikely that either of us will be exchanging furniture anytime soon" .. Bruce

    I couldn't find one point to dis-agree on in that statement as it pretty much "nails" it shut.

    Regards...

    Sarge..








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  7. #22
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    Jim, I've used pocket screws for face frames, but I don't understand how they're a good choice for assembling cabinet carcasses or drawers (instead of dadoes, etc.).

    How are these joints any stronger than butts joints with regular old drywall-type screws? I know that the pocket hole screws are easier to hide, but I don't get how they're any stronger. What am I missing?

    JW

    Quote Originally Posted by Jim Becker View Post
    I've switched over to pocket screws and wouldn't go back to dados/grooves at this point unless there was an unusual situation that warranted the extra work. Pocket screws and glue are quite strong and simple butt joints are far easier to size and cut than figuring the extra material to fit into the dados/grooves, etc. Pocket screws are essentially self-clamping after glue-up, too. (with care taken to avoiding racking while the glue fully cures)

  8. #23
    Quote Originally Posted by Jason White View Post
    How are these joints any stronger than butts joints with regular old drywall-type screws? I know that the pocket hole screws are easier to hide, but I don't get how they're any stronger. What am I missing?

    JW
    With the pocket hold screws, the end of the screw is penetrating 90 degrees to the grain. If you used regular screws from the opposite side, they'd be penetrating parrallel to the grain. A screw's resistance to pull-out is much greater across the grain than with the grain. Also, when you use the pocket hole method, the screw generally does a very good job of pulling the two pieces tightly together because it is only threading to the second piece, which helps the glue to do a better job. With a "normal" screw installation, the screw likely threads to both pieces, preventing it from pulling them together tightly.

  9. #24
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    By paying close attention to detail while machining dados, I cannot fathom an easier way to assemble a carcass. Add a couple of quick rabbets in the back of both sides and my glue-up literally squares itself up. I always run my stock twice through the dado blade. I start with a stack that is smaller then what I need...measure dado....move fence accordingly....perfect.
    It might just be me, but I always thought it a waste of time to get the stack the right size. Maybe it is the machinist in me....
    Gary K.

  10. #25
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    I prefer to use dados since I don't care for the look of pocket screws. Dados make alignment easy and are stronger than pocket screws although that isn't normally an issue. Since I don't make a living in my shop I don't care if it takes a little longer. I like to use dovetails and other time wasting joints in my shop as well...

  11. #26
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    Quote Originally Posted by Greg Funk View Post
    Since I don't make a living in my shop I don't care if it takes a little longer. I like to use dovetails and other time wasting joints in my shop as well...
    Not to hijack this thread but the above statement applies to me and probably some of the other people here as well. Why not use a more complicated joint that has a learning curve and apply what we've learned for other things. I think that's the way we teach ourselves. Most of what I do in my shop doesn't have an end user other than myself any way.

    Any way "on with the show".
    Making new friends on SMC each and every day

  12. #27
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    All joints should be planned and selected based on the amount, and direction of force that will be applied to the joint. Any joint that lack it's own mechanical integerity and relies on an adhesive alone will fail, on it's own, in time.
    The endgrain to facegrain butt joint is the second weakest joint there is. End grain to end grain butt being the weakest. It relies on the strength of the adhesive property, or the mechaincal strength of the fastener used.

    A dado provides a few mechanical functions;

    It provides for precise alignment.
    It provides shear load strength. ( resistance to force applied 90 degrees to the joint)
    It provides axial load strength.(resistance to twisting forces)

    The dado by itself is very poor for forces being applied in line with the joint. If you build a freestanding shelf with no backing, or individual shelf supports. Using only dados and rabbets. You have created a reflex parallelogram.
    Clamp the structure to a bench and push on the top corner and you will break it very easily. Glued and screwed will make it stronger, but the small amount of leverage applied will break even these joints.

    I personally would not use pocket screws alone. The strength is based on the properties of the screw, and the type of wood it's being screwed into. ( I wouldn't use drywall screws at all. They are made from a very brittle material and shear a lot easier than you might think.)

    For this project (the shelves, top, and bottom at least). I would dado the shelves, and bottom, rabbett the top, and screw and glue. I would screw from the face side into the dado joint.
    A pocket hole jig would provide less that 3/4" of screw engagment in the applicaion of attaching the shelves, top, and bottom to the sides. A screw gets it's mechanical strength from it's length. I'd be using 8-32 , or 10-32 screws,2" long, screwed into the joint.
    Build it stout, you won't regret it.



    In this project, http://www.sawmillcreek.org/showthread.php?t=63386 Every joint is a dado joint, that is screwed and glued (epoxied).
    The screws were screwed into the dado's from the face side, and wenge plugs cover the screwheads.
    The resistance to "racking" forces is provided by the back, which is a combination of individually rabbeted, shiplapped, and dado'd boards.

    My vote is Dado, glue, and screw.
    Use the pocket hole jig for the face frames.
    Last edited by Mike Cutler; 09-09-2007 at 11:08 AM.

  13. #28
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    I use both techniques and each has its place. I have not had any failures with pocket screws. I do like a rabbit on the rear of a cabinet to allow the back panel to set in....this squares the cabinet and adds strength. If your overall cabinet design and construction is thought out , the components all work well to add strength and no individual parts are stressed ....it all works together
    "All great work starts with love .... then it is no longer work"

  14. #29
    A couple of months ago one of the magazines did a strength test of different joints; biscuit, dowel, butt, dado, pocket hole and I think another one but I can't remember it. They tested shear and pull out. The winner was the dowel with pocket hole marginally less strong. If I can hide it, I use pocket holes.
    If sawdust were gold, I'd be rich!

    Byron Trantham
    Fredericksburg, VA
    WUD WKR1

  15. #30
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    Quote Originally Posted by Mike Cutler View Post
    All joints should be planned and selected based on the amount, and direction of force that will be applied to the joint. Any joint that lack it's own mechanical integerity and relies on an adhesive alone will fail, on it's own, in time.
    The endgrain to facegrain butt joint is the second weakest joint there is. End grain to end grain butt being the weakest. It relies on the strength of the adhesive property, or the mechaincal strength of the fastener used.

    A dado provides a few mechanical functions;

    It provides for precise alignment.
    It provides shear load strength. ( resistance to force applied 90 degrees to the joint)
    It provides axial load strength.(resistance to twisting forces)

    The dado by itself is very poor for forces being applied in line with the joint. If you build a freestanding shelf with no backing, or individual shelf supports. Using only dados and rabbets. You have created a reflex parallelogram.
    Clamp the structure to a bench and push on the top corner and you will break it very easily. Glued and screwed will make it stronger, but the small amount of leverage applied will break even these joints.

    I personally would not use pocket screws alone. The strength is based on the properties of the screw, and the type of wood it's being screwed into. ( I wouldn't use drywall screws at all. They are made from a very brittle material and shear a lot easier than you might think.)

    For this project (the shelves, top, and bottom at least). I would dado the shelves, and bottom, rabbett the top, and screw and glue. I would screw from the face side into the dado joint.
    A pocket hole jig would provide less that 3/4" of screw engagment in the applicaion of attaching the shelves, top, and bottom to the sides. A screw gets it's mechanical strength from it's length. I'd be using 8-32 , or 10-32 screws,2" long, screwed into the joint.
    Build it stout, you won't regret it.



    In this project, http://www.sawmillcreek.org/showthread.php?t=63386 Every joint is a dado joint, that is screwed and glued (epoxied).
    The screws were screwed into the dado's from the face side, and wenge plugs cover the screwheads.
    The resistance to "racking" forces is provided by the back, which is a combination of individually rabbeted, shiplapped, and dado'd boards.

    My vote is Dado, glue, and screw.
    Use the pocket hole jig for the face frames.
    Hi Mike,

    You make a lot of sense here. I like PHS but like you I feel they don't engage the second piece of wood with much screw length. I like #8 2.5" screws for assembling shop carcases using glue.

    One question: How do you match your dado blade width to your plywood thickness? This is on of the major pains of dadoing to me. Alan
    Alan T. Thank God for every pain free day you live.

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