Using 5/16 zinc threaded rod as dowels. - Woodworking Talk - Woodworkers Forum
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post #1 of 15 Old 02-20-2016, 02:23 AM Thread Starter
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Using 5/16 zinc threaded rod as dowels.

Hi. What's up guys. I am in the way of joining some 2x4 joints. I decided to go with dowels, but not with hardwood dowels, but zinc threaded rod, which is amazingly strong and has very good price. 5/16 x 24" about $1.75 dollar.

I was planning cutting the rod into 4" segments, so I can use them to join the 2x4s. The good thing about this, is that we are getting something VERY strong, in a very compact factor, I mean, a very solid thing, hard to bend it, and because of the small factor, less wood should be removed to host the dowel.

There are two types of zinc rods, threaded and fine, I think that definitely should go for the threaded one, just because glue will be required, and because of the threads, it will hold it better as any other way. Actually only in half of the dowels glue may be required, because you can screw half of the dowel, and then glued into the same diameter hole, actually I don't know if you can go with both holes, a little less of the rod diameter, so you can push hard both pieces.

Is this usually used in woodworking? if so can I get some advices?

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post #2 of 15 Old 02-20-2016, 02:55 AM
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That seems pointlessly elaborate to me. Ignoring the fact that youll have a hard time getting a good glue bond between wood and metal in the first place, and that any adhesive thatll stick the 2 together will be way more expensive and not as strong as wood glue, and the fact that you can buy or make wooden dowels for less than a quarter of the cost of the all-thread, the strength you can get from even a 1/4 dowel is already pretty bloody strong, theres not really much room for improvement there.

So no, not usually used in woodworking, and for good reason.
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post #3 of 15 Old 02-20-2016, 06:39 AM
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Originally Posted by epicfail48 View Post
That seems pointlessly elaborate to me. Ignoring the fact that youll have a hard time getting a good glue bond between wood and metal in the first place, and that any adhesive thatll stick the 2 together will be way more expensive and not as strong as wood glue, and the fact that you can buy or make wooden dowels for less than a quarter of the cost of the all-thread, the strength you can get from even a 1/4 dowel is already pretty bloody strong, theres not really much room for improvement there.

So no, not usually used in woodworking, and for good reason.
+ 1.

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post #4 of 15 Old 02-20-2016, 07:23 AM
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You may think you are making a better joint by using threaded rods for dowels but unless you go all the way through the wood and put a nut and washer on each end you will create a weaker joint. A well fitted wood dowel will be far stronger than a piece of steel.
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post #5 of 15 Old 02-20-2016, 04:23 PM Thread Starter
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I expected some answers like these, but I still have my doubts. I don't know, I mean, you may be right when you say that hardwood dowels can be pretty strong, but I imagine the threaded rod with also some benefits, like the compact factor (less wood removed), and because of the threads, we have an interesting surface area where glue can seat and hold, specially if you clean it with a metal brush before applying the glue, glue that can be titebond 3, not epoxy or any other expensive one. I have used titebond 3 more than bonding woods, I also tried to glue PVC to PVC using it, the bond was incredible strong, i simply could not take it apart, now imagine the glue seated in the threaded rod.

I was planning doing two things with the rods, first one was using it as dowels, and second as, i don't exactly know how to call this, but I also need to insert a 4" threaded rod, 2" deep in the wood, that way half of the rod remain external, I need this point to then insert a board with a hole, and then I add a washer and a nut, I found this method great for some book shelfs that I am doing, because because of the inserted threaded rod, they can be used as a guide while placing the shelf level into the main columns. I mean, the column has 2 holes, that receives the threaded rods that are inserted into the shelves, that permits you to arrange and place everything and then add and tight the nuts. So here glue is important so the threaded rod is perfectly holded by the wood, so it won't rotate when tightening the nuts. I think that titebond 3 is just as amazing as epoxys are, the only bad thing is the set time, we need one day in order to get the maximum strength.

Last edited by Johanx3; 02-20-2016 at 04:25 PM.
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post #6 of 15 Old 02-21-2016, 12:03 AM
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In your second scenario why wouldn't you just use a hanger bolt that threads in like a lag bolt only it has threads on the opposite side? Relying on WOOD glue to hold metal seems pretty risky to me.
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post #7 of 15 Old 02-21-2016, 01:11 AM Thread Starter
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In your second scenario why wouldn't you just use a hanger bolt that threads in like a lag bolt only it has threads on the opposite side? Relying on WOOD glue to hold metal seems pretty risky to me.
I did not know such thing, anyway I would need many of them, at least 50, which increases the cost unnecessarily compared to the idea of cutting threaded rod segments and simply glue them in the hole with titebond. These carpenter glues are actually stronger than wood, so I think it's not a bad idea to glue them. I will clean the rod and add a gently quantity of glue. Also to mention that the rod segments will be placed horizontally, so the the load will not be pushing it as trying to remove the rod from 90 angle degree. Anyway will do some tests observing how hard is to remove the glued rod by tightening a nut, let's see what happen first, the rod being removed cleaned, or the wood piece being broken because the rod was pretty attached to wood. I will try to record a video of the test.
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post #8 of 15 Old 02-21-2016, 06:14 AM
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He has his mind made up, so why did he bother posting?

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post #9 of 15 Old 02-21-2016, 06:42 AM
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I'm with you GeorgeC!!!!!!!
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post #10 of 15 Old 02-21-2016, 10:15 AM
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Quote:
Originally Posted by Johanx3 View Post
I did not know such thing, anyway I would need many of them, at least 50, which increases the cost unnecessarily compared to the idea of cutting threaded rod segments and simply glue them in the hole with titebond. These carpenter glues are actually stronger than wood, so I think it's not a bad idea to glue them. I will clean the rod and add a gently quantity of glue. Also to mention that the rod segments will be placed horizontally, so the the load will not be pushing it as trying to remove the rod from 90 angle degree. Anyway will do some tests observing how hard is to remove the glued rod by tightening a nut, let's see what happen first, the rod being removed cleaned, or the wood piece being broken because the rod was pretty attached to wood. I will try to record a video of the test.
I would like to see the results of your tests. I have repaired several old chairs where the wood dowels failed by substituting threaded rod with good success. I also did some tests. I drilled a 3/8" hole 2" deep into the end grain of an oak block 1.5"x1.5"x6" I filled the hole with titebond and screwed in the dowel. I clamped the block in a vise and put a sleeve over the rod sticking out and bent . The rod bent but withstood a force much greater than a wood dowel could. I then put a washer and nut on the rod and tightened. The rod did not pull out and eventually the block cracked allowing the rod to turn. Conclusion-steel rod much stronger than a wood dowel.
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post #11 of 15 Old 02-21-2016, 01:24 PM
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Originally Posted by Zircon View Post
I would like to see the results of your tests. I have repaired several old chairs where the wood dowels failed by substituting threaded rod with good success. I also did some tests. I drilled a 3/8" hole 2" deep into the end grain of an oak block 1.5"x1.5"x6" I filled the hole with titebond and screwed in the dowel. I clamped the block in a vise and put a sleeve over the rod sticking out and bent . The rod bent but withstood a force much greater than a wood dowel could. I then put a washer and nut on the rod and tightened. The rod did not pull out and eventually the block cracked allowing the rod to turn. Conclusion-steel rod much stronger than a wood dowel.
"Conclusion-steel rod much stronger than a wood dowel."

Your conclusion is obvious without any study.

However, unneeded in wood work.

George
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post #12 of 15 Old 02-21-2016, 01:42 PM
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What you have to understand about a wooden dowel in a joint is that it's purpose is to hold the joint together. The glue soaks into the fibers of the wood and turns to a plastic more or less making the wood one. With a piece of steel, it will always be a foreign substance which requires a mechanical bond which is difficult even using an epoxy. Even when they build cars where they are attaching a rear quarter panel with an epoxy the joint is mainly done with rivets or spot weld. The epoxy is there just to eliminate slight movements which would show up in the paint.
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post #13 of 15 Old 02-21-2016, 02:31 PM
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The steel dowel joint is definitely stronger than the wood dowel joint. That is why I used steel to repair the dowel jointed chairs where the wood dowels had failed in normal use. The only downside to the steel dowel joint is when your 300 pound brother in law tips his (your)chair back on two legs, the chair leg will blow out instead of the wood dowels just failing.
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post #14 of 15 Old 02-21-2016, 02:37 PM
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What is the item going to be? I agree that it seems pointless to me.

Couple of points, the dowel (whether) metal or wood will not strengthen the joint in any manner. A well made glued edge joint is stronger than the wood itself. Dowels, biscuits and splines are fine for alignment but do nothing to make the joint stronger.

Potentially your doweling plans can cause another problem. The wood is going to want to expand and contract with changes in moisture content. The steel rods are not going to move. The forces this generates will likely cause the wood to split or be otherwise damaged.

Bottom line, I think it's a bad idea.

Howie..........
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post #15 of 15 Old 02-21-2016, 05:05 PM
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Originally Posted by HowardAcheson View Post
What is the item going to be? I agree that it seems pointless to me.

Couple of points, the dowel (whether) metal or wood will not strengthen the joint in any manner. A well made glued edge joint is stronger than the wood itself. Dowels, biscuits and splines are fine for alignment but do nothing to make the joint stronger.

Potentially your doweling plans can cause another problem. The wood is going to want to expand and contract with changes in moisture content. The steel rods are not going to move. The forces this generates will likely cause the wood to split or be otherwise damaged.

Bottom line, I think it's a bad idea.
Agree, there seems to be no upside and many reasons why after all these years it is not a common method of dowelling.

Wise men speak because they have something to say; fools because they have to say something -Plato

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