Page 1 of 3 123 LastLast
Results 1 to 15 of 34

Thread: Dowel Joinery?

  1. #1

    Dowel Joinery?

    So I saw a youtube video recently about dowel joinery which reminded me that I've seen almost no discussion of it. It appears to fill a similar niche to the Festool domino, while not requiring a very expensive unitasker. It also appears to be stronger than pocket holes, or biscuits and fill a similar niche.

    I just assembled a few simple panel glue ups with it, using this cheap jig, and it appears to have worked as well as biscuits or dominions for doing alignment, with the advantage that it appears to add strength in a way that biscuits do not. If you don't want to spend the $20 for the jig, there are instructions in this video on how to make your own.

    Any ideas why dowels don't get much attention, while pocket holes, and more traditional joinery techniques, such as dovetails, and mortise and tenon appear to be all the rage? Is there a serious draw back that makes the domino the superior tool for this? I'm guessing the domino makes a stronger joint, but not sure by how much, and how significant that difference is.

  2. #2
    Dowel Joinery rocks!

    I hate to use the term better or worse, all I'm saying is dowel joinery has been a great method to have in my repertoire.

    In answer to your question, commercial furniture has contributed to giving dowels a bad name. In a factory setting they are using machinery to squirt a glob of glue in the dowel hole, and then another machine to push in a dowel. The result? A glob of glue at the bottom of the dowel hole and the vast majority of the dowel body dry and unglued. These are the dowel joints that come apart and make people curse dowels.

    An attentive woodworker on the other hand is coating the dowel hole (I use cotton swabs like long Q tips) and also coating the dowel itself before inserting and then clamping the joint together. This is a very different scenario than the factory one I describe above.

    I happen to have a Jessem Doweling jig which is a superb piece of kit. However for many projects, I end up making a shop made doweling jig for the specific purpose.

    Edwin

  3. #3
    Quote Originally Posted by Edwin Santos View Post
    In answer to your question, commercial furniture has contributed to giving dowels a bad name. In a factory setting they are using machinery to squirt a glob of glue in the dowel hole, and then another machine to push in a dowel. The result? A glob of glue at the bottom of the dowel hole and the vast majority of the dowel body dry and unglued. These are the dowel joints that come apart and make people curse dowels.
    Good to know, I must admit to falling into that error. I'll avoid it in the future. However I'm also making a panel, so lots of glue along the edge, so I don't think it's going to come apart, but next time I'll be more attentive to glue in the hole as well.

    Quote Originally Posted by Edwin Santos View Post
    I happen to have a Jessem Doweling jig which is a superb piece of kit. However for many projects, I end up making a shop made doweling jig for the specific purpose.
    Thanks for the pointer to the Jessem doweling jig. Seems far superior to the cheap piece of plastic I've been using. Can you post some pics of your hand made jigs? I'm curious as to their construction, and how you ensure high levels of accuracy with them.

  4. #4
    Dowels have their place but they're not as strong as mortise and tenon. I've posted the mathematics several times here.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  5. #5
    Instead of a fancy drill guided jig, use a plunge router with up spiral bit and a shop made guide. Guide is simply a piece of wood with a couple holes drilled to accept guide bushing and a fence

  6. #6
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    6,363
    For edge joints you don't need anything for strength and dowels won't add to the strength of a glued edge joint. However, you may choose to use dowels, biscuits, whatever, to help align edge joints. I often use biscuits because they are fast.

    My beef with dowels is they are slow compared to other joints, and require very high precision for perfect alignment of the mating parts, and it grows nearly expotentially the more dowels you have in a joint. I've seen folks show 8 dowels in some joint, all perfectly aligned. Great, but how long did it take to make compared to a Domino or loose tenon joint? For most applications other joinery techniques are just easier and faster for me, so the only time I use dowels is where they are about the only option, like some chair joints where you are working with pieces of small cross section.

    John

  7. #7
    Quote Originally Posted by Edwin Santos View Post
    In answer to your question, commercial furniture has contributed to giving dowels a bad name. In a factory setting they are using machinery to squirt a glob of glue in the dowel hole, and then another machine to push in a dowel. The result? A glob of glue at the bottom of the dowel hole and the vast majority of the dowel body dry and unglued. These are the dowel joints that come apart and make people curse dowels.

    Edwin
    I'm afraid this is not true. I've repaired a lot of chairs that use two 3/8 inch dowels between the seat and the back. The failure is not from lack of glue. The chair manufacturers are not incompetent and do coat the dowels quite well with glue.

    The failure method is not glue failure but wood failure - the wood that the glue is attached to actually breaks.

    The problem with dowels on that chair joint is that there simply is not sufficient long-grain-to-long-grain glue surface area. A tenon that will fit into the space of two 3/8 inch dowels has quite a bit more long-grain-to-long-grain surface area and thus provides a stronger glue joint. I'll post the mathematics (again) if you have questions or doubt if this is true.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  8. #8
    Only failure on dowels is time. Almost anything can fail in time. Old glues, wrong glues,not enough glues, too much moisture... Any number of reasons.

    When you build something hut simple care to do the best you can to prevent future problems...

  9. #9
    Ive used them. We would cut them from dowel rod, didn't use the spiral stuff. We would drive them thru a 1 inch thick
    piece of scrap steel that had different sized holes. The sharp edges on the steel were beveled off with a countersink.
    The plate did no cutting ,only squeezing. We thinned the the glue just a little. The dowels went in easily and swelled
    quickly.

  10. #10
    Join Date
    Mar 2006
    Location
    SoCal
    Posts
    19,847
    As you have probably gotten from the responses; they have their place. Many joinery methods can be interchangeable for a given set of requirements. You can search here and elsewhere for near-endless discussion on the long grain to long grain versus round and flat "objects de' joinery". Some of us have love or hate relationships with certain things like dowels, biscuits or whatever. These feelings are built through experiences. I would argue that many joinery types can be misused and provide sub-optimal performance whether in strength, durability or fussiness ;-)
    “Falsehood flies, and the Truth comes limping after it,”
    -Jonathan Swift

  11. #11
    Quote Originally Posted by Mike Henderson View Post
    I'm afraid this is not true. I've repaired a lot of chairs that use two 3/8 inch dowels between the seat and the back. The failure is not from lack of glue. The chair manufacturers are not incompetent and do coat the dowels quite well with glue.

    The failure method is not glue failure but wood failure - the wood that the glue is attached to actually breaks.

    The problem with dowels on that chair joint is that there simply is not sufficient long-grain-to-long-grain glue surface area. A tenon that will fit into the space of two 3/8 inch dowels has quite a bit more long-grain-to-long-grain surface area and thus provides a stronger glue joint. I'll post the mathematics (again) if you have questions or doubt if this is true.

    Mike
    Not true?

    Well here's my source (besides my own experience) - an article written by Bob Flexner, a well known published woodworker whose article mentions Brian Boggs, also a well known published woodworker: https://www.popularwoodworking.com/f...se-so-quickly/

    By the way, I am in no way saying dowels are "better" than a mortise and tenon, or any other kind of joinery for that matter. However I do not agree with sweeping nature of your conclusion regarding one being inferior to the other. While I understand the long grain to long grain surface concept, in reality if the dowel joint is well made and well glued, they are more comparable than your statements would suggest. As a source to further elaborate on what I am saying, here is a link to the tests Matthias Wandel did measuring the strength of the two types of joinery: https://woodgears.ca/joint_strength/dowel.html

    I do think a mortise and tenon joint in most circumstances will be stronger, but not radically so. In my own woodworking I tend to use dowels in applications and places where a mortise and tenon would not be possible or practical. In applications that lend themselves to mortise and tenon joinery, I use a mortise and tenon.

    Edwin

  12. #12
    Join Date
    Jun 2013
    Location
    US Virgin Islands
    Posts
    3,300
    Blog Entries
    6
    These doors were doweled with the JessEm doweling jig I bought from
    another creeker. I was skeptical, but really loved it. I also used it to repair some mahogany doors. The repair was doweled for strength.

    7C0E0E50-9D2C-4475-B70A-B32A9A59E14C.jpg

  13. Yes they have their place no matter what you might read. I keep spirals on hand and also have a store bought dowel plate that grooves them as i cut to length. This allows keeping a general stock of long hardwood dowels at hand for ready use. Lowe's keeps them on the back aisle in several woods- I buy oak ones there on my 10% vet discount.

  14. #14
    Quote Originally Posted by Edwin Santos View Post
    Not true?

    Well here's my source (besides my own experience) - an article written by Bob Flexner, a well known published woodworker whose article mentions Brian Boggs, also a well known published woodworker: https://www.popularwoodworking.com/f...se-so-quickly/

    By the way, I am in no way saying dowels are "better" than a mortise and tenon, or any other kind of joinery for that matter. However I do not agree with sweeping nature of your conclusion regarding one being inferior to the other. While I understand the long grain to long grain surface concept, in reality if the dowel joint is well made and well glued, they are more comparable than your statements would suggest. As a source to further elaborate on what I am saying, here is a link to the tests Matthias Wandel did measuring the strength of the two types of joinery: https://woodgears.ca/joint_strength/dowel.html

    I do think a mortise and tenon joint in most circumstances will be stronger, but not radically so. In my own woodworking I tend to use dowels in applications and places where a mortise and tenon would not be possible or practical. In applications that lend themselves to mortise and tenon joinery, I use a mortise and tenon.

    Edwin
    Okay, here's the math.

    Let's take dowels that are 3 inches long, 3/8 inches in diameter, and two are used in the rear of a chair joint.

    To compare to a tenon, we'll look at the length of the dowel that's in one side. The tenon is solid wood on one side of the joint.

    The formula for the surface area of a cylinder is 2*pi*r*h. In this situation, r is 3/16 and h is 1.5 inches so the area of the cylinder is 1.767 sq inches. Since we have two dowels, the total area of the two dowels is 3.534 square inches.

    However, only half of that area is long-grain-to-long grain surface area. You can visualize this if you think of the dowel as a square dowel of the above surface area - half will be facing long grain and half will be facing end grain.

    So the long-grain-to-long-grain surface area is 1.767 square inches.

    Now let's look at a tenon that will fit into the same space. The first question is how far apart are the two dowels. The further apart they are, the wider the tenon can be to fit into the same space. So let's assume the two dowels are close together. On chairs they aren't but let's do it this way to be conservative - let's assume the two dowels are 1/8 inch apart.

    So the tenon can be 3/8 + 3/8 + 1/8 inch wide, or 0.875 inches. Since the tenon is going to be 1.5 inches long, the surface area of one face is 1.3125 sq inches. The tenon has two faces so the total long-grain-to-long-grain area is 2.625 square inches. This is 48.5% greater than the long-grain-to-long-grain surface area of two dowels and provides significantly greater strength.

    Note that in the real world dowels on chairs are spaced further apart than 1/8 inch so the area of the equivalent tenon is going to be greater, giving a much higher long-grain-to-long-grain surface area.

    I have a spread sheet that computes this if anyone would like to play with the figures.

    Mike

    [All the chairs that I've repaired have had two dowels at that rear joint and the failure was wood failure, not glue failure. I've never had to repair a joint that was M&T. Two dowels just don't have enough glue surface area for that joint.]
    Last edited by Mike Henderson; 01-15-2020 at 1:22 PM.
    Go into the world and do well. But more importantly, go into the world and do good.

  15. #15
    Quote Originally Posted by Mike Henderson View Post
    Okay, here's the math.



    Mike

    [All the chairs that I've repaired have had two dowels at that rear joint and the failure was wood failure, not glue failure. I've never had to repair a joint that was M&T. Dowels just don't have enough glue surface area.]
    Thanks for the math. Sounds good in theory.

    Do you have a comment on the source articles from Flexner and Wandel?
    Wandel's test in particular reveals a real world outcome very different from what your math implies (in theory).

    Ironically I repaired a chair about three weeks ago that the customer bought from Restoration Hardware. The mortise and tenon joint failed. There appeared to me to be two problems. One was that the mortise and tenon joint had left so little "meat" on either side of the mortise that it broke right through the back leg. The other looked to be what might have been insufficient glue.

    Again, not lobbying for one kind of joinery over another 100% of the time.
    One thing people don't always consider with a mortise and tenon joint is the wood that's being removed from one member and whether there is sufficient surrounding wood left to handle whatever load is transferring through the tenon. When I've seen mortise and tenon failures it's been for this reason primarily. I think both types of joinery have their place. The key is to use each one where appropriate.

    One other point, I think two dowels, especially if they were not coated completely with glue, may be culprit behind your repairs more than the whole method of joinery being unsound. One thing I like about the Jessem system is the ability to do rows of dowels, in an offset pattern to minimize surrounding wood failure. If the chairs you have been repairing had been joined with a row of three or four dowels and both the hole and dowel were brushed with glue like you or I would do in our shops, I think you would see fewer failures. Again, I'd reference you to Flexner's article who does a better job of explaining it.

    Edwin

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •