Dowel holding 5 2x4 boards - Woodworking Talk - Woodworkers Forum
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post #1 of 13 Old 02-04-2016, 09:15 PM Thread Starter
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Dowel holding 5 2x4 boards

Hello guys, after thinking ways to join five little 2x4 boards (I don't know why they call them 2x4, when they actually are about 1.5x3.5, first I thought that they were wrong labeled and I did not get 2x4 instead, then found that those dimensions are ok for 2x4 lumber...). Well, now the technical question. I don't know which dowel diameter size would be the correct. I am going to use either 1-1/4 (32mm) or 1-1/2 (38mm) dowel. Considering the wood surface is (3.5") 89mm, if I planning giving one third of the surface to the dowel, then I found than 89 / 3 = 29.6mm, then my proper option is the 1-1/4 (32mm) dowel ? or is it better the 1-1/2 (38mm) although is passes the third portion of the surface? I need this piece very strong, because it's the base of a multilevel shelf. In the picture below you can see my arrange, ignore those large screws, I am still not sure if necessary or just ok with the dowel only.

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post #2 of 13 Old 02-04-2016, 09:24 PM
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2x4's are called that because that was the size they were originally cut from a tree. My parents house was made with rough sawn lumber that was 2" thick and 4" wide. Then someone came up with the idea of surfacing the saw marks out so they just took the 2x4 inventory they already had and surfaced the saw marks off. Over the years they are just fudging more and more making the wood thinner to get more boards out of a log but the name remains the same.

Your picture didn't come through so I don't understand completely what you are doing. If the joints are well made there is no reason to use dowels. Just use wood glue and clamps and the panel will be as strong as if it were a single piece of wood.
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post #3 of 13 Old 02-04-2016, 09:40 PM
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I suggest you go back to where you purchased the 2X4's and buy some closet rod.
The CR will be larger in diameter than dowels. Cut to length. Badda boom badda bam.
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post #4 of 13 Old 02-04-2016, 10:43 PM Thread Starter
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I am trying to discover if there is a rule for the dowel size. After all I think I am going with 1-1/4 dowel size, that represents about the third part of the surface area, I think that there should be a balance, I cannot go for example with a 3" in dowel, because I will reduce the mass of the body. I still dont have it so clear, but I think that one third should be ok, don't know if half proportion is even better.
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post #5 of 13 Old 02-04-2016, 11:01 PM
where's my table saw?
 
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you don't need dowels

If you glue 5 squares or small pieces of flat, even wood together and clamp them until the glue dries, you won't need any dowels. The glue joints will not break, but the surrounding wood will.

If you want a centering post, then a dowel is fine for that, but not necessary for strength. On a 3" square, I would use a 1" dowel. The dowel is a hardwood, the construction lumber is soft wood. The dowel is stronger than the soft wood, so it can be smaller in proportion.

Check this out:
http://woodworkingtips.com/etips/etip40.html
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The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 02-04-2016 at 11:05 PM.
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post #6 of 13 Old 02-04-2016, 11:12 PM
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Is the multilevel shelf raised up on that dowel or is that dowel part of the glue joint for the shelf?

How big is that multilevel shelf?
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post #7 of 13 Old 02-04-2016, 11:34 PM Thread Starter
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Of course I can simply glue all the boards without using any dowel, but the structure will be "more fragile". The external dowel it's supposed to match a hole in a board (first level, i need 2 holes because my 2 columns are mono axis, its an experiment I am trying, using 2 columns total, each column will act as a big screw, I have been working on this since 2 weeks ago, a little hard because I want it detachable, and very easy to build, simply rotating each column.
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post #8 of 13 Old 02-04-2016, 11:41 PM
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Really dowels are not going to help the strength of the base. As much wood as there is in the illustration you could park a tank on it. That's as much as the trunk of a big tree.

The external dowel might be a good idea but without knowing the details of the multilevel shelf that sits on it it would be difficult to say what size to use.
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post #9 of 13 Old 02-05-2016, 12:14 AM Thread Starter
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One foot is basically a block of four 3.5 x 16", actually five block sections, but as you can see the image, the last foot level only has two square pieces, then I thinking if adding four 1-1/4 dowels passing through all the body piece, I think that should be enough strong to support even a cow, don't you think?
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post #10 of 13 Old 02-05-2016, 08:54 AM
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So if I'm looking at this right, you basically have a bunch of 2x4s of different lengths, laid flat and then stacked up, all glued together?

It would be helpful to post a picture of the entire project.

Those 2x4s glued together by their wide faces will be incredibly strong, IF you can get them flat enough. Once glued, they will never move.

The dowel is primarily to assist in aligning the next section on top, like bunk beds?

But you are asking whether drilling through the center of all the stacked up 2x4s, and extending that same dowel all the way through will add any strength?
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post #11 of 13 Old 02-05-2016, 10:16 AM
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I'll make it real simple.It is only the 11th post for a simple question about a dowel.Pretty goo for this board.A dowel sized at 1/3 of the surface area will be fine.
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post #12 of 13 Old 02-05-2016, 10:32 AM
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yes, that's the simple answer

Quote:
Originally Posted by mako1 View Post
I'll make it real simple.It is only the 11th post for a simple question about a dowel.Pretty goo for this board.A dowel sized at 1/3 of the surface area will be fine.

Here's the bigger picture.
Op comes along and post 2 identical, 3 color images, the green color only adding to the confusion.
Then asks the question which you answered.
End of discussion... right? Not really.

OP states:
One foot is basically a block of four 3.5 x 16", actually five block sections, but as you can see the image, the last foot level only has two square pieces, then I thinking if adding four 1-1/4 dowels passing through all the body piece, I think that should be enough strong to support even a cow, don't you think?

Why do you need all that strength, and from what direction are the forces, just vertically downward or latterally? There is no real explanation for what the dowel does. Does it "bind" the glued up sections, or act as an alignment post, or do other pieces rotate on it? In attempting to answer the original question other question are raised. As usual, insufficient information, descriptions and images raise additional questions.

If the "simple" answer is all the OP needs, then he has his answer.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #13 of 13 Old 02-05-2016, 10:03 PM
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Quote:
Originally Posted by Johanx3 View Post
I am trying to discover if there is a rule for the dowel size. After all I think I am going with 1-1/4 dowel size, that represents about the third part of the surface area, I think that there should be a balance, I cannot go for example with a 3" in dowel, because I will reduce the mass of the body. I still dont have it so clear, but I think that one third should be ok, don't know if half proportion is even better.
As Hillary would ask, "What difference does it make?"
It won't be seen. It's for assembly/disassembly.
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