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Very Large Dowel Joins

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Forum topic by ruddhess posted 02-13-2015 03:10 AM 1004 views 0 times favorited 13 replies Add to Favorites Watch
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ruddhess

117 posts in 672 days


02-13-2015 03:10 AM

Topic tags/keywords: laminate slab dowel all-thread gluing cross laminated timber benchtop

I’m new here and working on a laminate “slab” (sort of Japanese style work surface is the intention). Has anybody here used (as in 5/8” or 3/4”) dowels to join 2X lams? I am using 3/8” all-threads to pull my benchtop lams (center ripped 2 X 10 X 72) together for gluing (no clamps – el cheapo special). But I don’t want to leave any steel/iron in the wood. So I was wondering about trying to use large dowels in the thru-holes that I drill transversely through the 2 X 4-1/2 bench top lams. I did a search on the web and read about some Europeans doing their “green” thing with “cross laminated timber” stuff. I don’t think it’s really new, but seems to be popular there. I’m not sure that I can actually drill the holes separately in each laminate accurately enough for the dowel not to get hung up along the way. Just wondering if anyone has tried this yet and what kind of results they got. I may experiment after I get my “board” glued up (initially it will be only 18” wide if that matters). Thanks!
Rodney in Arkansas

-- Rodney, Arkansas


13 replies so far

View richardwootton's profile

richardwootton

1699 posts in 1417 days


#1 posted 02-13-2015 04:46 AM

Rodney, if the boards are jointed well you can probably just do a rub joint and add some weight to close any gaps you have. It seems like that could eliminate the need for screws and or dowels. And I have to apologize, I’m not familiar with a Japanese work surface. Out of curiosity, where in Arkansas are you?

-- Richard, Hot Springs, Ar -- Galoot In Training

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bobro

308 posts in 773 days


#2 posted 02-13-2015 05:46 AM

If you took a 3/4” square by 18” long board and glued it across the face of 9 laminated two-bys, everyone would say hey that’s a cross-grain construction, it’s going to split some day! And they’d be right. A 3/4” dowel glued inside the laminate crosswise is the same cross-grain construction but with 3.14 times the gluing surface.

You could run dowels through crosswise and get the mechanical resistance to cupping and twisting you want without splitting if you used the same principle as a batten. The dowel would have to be a little shorter than the width to allow contraction, and glued or otherwise fixed only at one end allow expansion.

If the moisture content of the wood was about at a seasonal average during construction, a 17+1/2” long dowel would allow a full inch of overall movement (+/- 1/2”). You could put a plug over the end where the dowel is short for aesthetic purposes.

Now someone is going to point out some particular piece of furniture with cross grain construction that has not split is so and so many years. We’ve probably all seen such things. I’ve made such things, though I wish I hadn’t. In indoor applications with certain tropical woods used for flooring you can get away with stuff. Softwoods which are stable and have “give” and flex also let you get away with stuff. In calm semi-arid climates you can get away with all kinds of shenanigans. But in the long term and big picture, cross grain construction is bad.

CLT is basically giant plywood and like plywood balances out movement/restriction in multiple layers. In the CLT beams I’ve seen, you can see from the end grain that they’ve also balanced out the grain orientation of the layers deliberately, like > I < if that makes sense. Same idea as smile/frown/smile… on a flatsawn tabletop.

Hope this is helpful.

-- Lao Ma: You are so full of anger and hatred. Xena: Everybody's gotta be full of something.

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ruddhess

117 posts in 672 days


#3 posted 02-13-2015 05:50 AM

Hi Richard,

I’m in Centerton, by Bentonville. I’m essentially making a benchtop with the idea of just setting it on some trestles. Similar to this:

I have only ripped each one down the center. No planing or jointing. This one will be a bit rough. I just need something heavy and solid to work on. That’s why I’m strongly considering using the liquid nails instead of wood glue. And with the all-thread, I can get a really strong and tight “pinch” every 14”. I’m not against using the clamps, I just don’t have the budget yet. I’d rather buy wood and make stuff first. As you have probably experienced, this area is rife with antique and flea markets that still have a fairly good bounty of used hand tools. Thus I am eyeballing a couple or three (or a half dozen) old planes! That’s where my “expendable” income is going lately. I’m not a collector, I just enjoy going out and finding cool stuff to use to make things with. If I am REAL careful, I think I can get some holes that line up well enough to use big dowels to join the laminations (my idea is really to cinch with all-threads already purchased, then remove them when the adhesive cures well and replace the all-thread with big dowels). I think it would be a decent way to join wood. I could use a long auger to drill through all the boards together perhaps, but I don’t think the bore would be straight. There should be ‘just enough’ off-set of the holes by drilling each board separately to create a ‘just enough’ tension on the dowel to hold everything together well – and in conjunction with glue, the join should be really strong (I know that I’ll have to whittle the end down like a pencil so it will guide in without snagging on a small shoulder inside). I’m going to test it out anyway. I don’t think this is a new idea by any means though. I will take pictures and post results as I go along. We had some very nice weather recently to go out into the garage and work, but it’s a bit nippy here now! Thanks for your input Richard. I really like the idea of using weights to hold stuff down. I used to have a bunch of weightlifting weights, but I got rid of some a while back. I might visit the local steel & pipe supply sometime to try and find a nice big thick steel plate for woodworking. Not sure what steel is going for now, but I bet it’s less than what “weights” sell for at PlayItAgainSports or WM. And for that kind of money I can get some clamps at HF eventually.
Cheers,

-- Rodney, Arkansas

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ruddhess

117 posts in 672 days


#4 posted 02-13-2015 06:09 AM

Oh bobro,
So much excellent information! Thanks. I’m having such fun being in way too much of a hurry to let my store bought lumber dry very much, LOL. So from what you said about cross grain construction, it would probably be better to use the all-threads as “clamps” while the adhesive cures and then take them out so everything can expand and contract with drying and weather changes? Perhaps those holes are a good thing for air to get inside? I also thought about making them 3/4” holes and getting a couple of Grammercy Tools holdfasts and use them in the holes already in the slab. Not very “Japanese”, but I’m all in favor of mixing my cultural influences if whatever I’m doing “works”. I’m no purist. I like synthesis. Eventually I’ll probably make another slab just like this one and combine them to make a “regular” workbench. I inherited an old “leg” vise (except it has both sides of the jaws attached as part of the vise – but it looks like a leg vise and doesn’t have a shoulder, so I don’t think it is technically a shoulder vise) and I’d like to be able to use it on a workbench someday. Here’s a picture of it:

And here is one I found just last weekend at a local flea market for $10 – I thought it was an exceptional buy:

Also, somewhere in one of my many boxes, I have a vintage wood lined jaws bench vise that I thought about putting on a workbench too. Again, thanks very much for your input and your knowledge. Awesome.
Cheers,

-- Rodney, Arkansas

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bobro

308 posts in 773 days


#5 posted 02-13-2015 10:15 PM

hey ruddhess, no problem. You won’t want to leave the holes- if you drill ithrough a board crosswise and take a look inside, you’ll see that you’ve exposed almost entirely end grain. That means that four 3/4” holes crosswise through an 18” slab would expose something like 100 additional square inches of endgrain.

If you just wanted to dessicate a wet board in a hurry for some reason, that would work. Unfortunately the same way moisture mostly leaves a board is the same way it mostly goes back in as the humidity changes with the weather: through endgrain.

So although leaving holes wouldn’t have too dramatic an effect on the mechanical strength of the beam, you’d be asking for trouble with movement as the moisture content of the wood zoomed up and down via all that exposed end grain. You usually want to cover endgrain, not expose more, except as a deliberate aesthetic choice, which has to be thought out in terms of what’s going to move.

You could slather epoxy inside your bore hole but somehow that just seems wrong. In your case, why not just clamp it up with the rods if you want, then put a dowel in there without glue, then countersink a nice decorative plug over the ends? At 17” the dowel would leave you enough room for both movement and for the countersinks for the plugs.

I really like your beam-on-horses approach, it looks great and it sure works for countless woodworkers in Asia.

-- Lao Ma: You are so full of anger and hatred. Xena: Everybody's gotta be full of something.

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ruddhess

117 posts in 672 days


#6 posted 02-14-2015 01:35 AM

Thanks very much bobro for your input.

I never thought about the bored holes being mostly end grain before. Sure enough it would be a lot of end grain exposed to the air as you say. I read on LJ just recently about thinking of wood as a bunch of cellulose straws/tubes all connected together in a bundle just sucking in the moisture and any water they might come into contact with (just like trees that absorb water in the ground through the roots up through the trunk and so forth).

I think that I will take your advice and plug 17” dowels into the holes without glue (after I pull the threaded rod out) and finish up with decorative plugs in the ends. That sounds like it will look good.

I ended up buying a 5/8” Irwin Speedbor bit to make the holes with. My plan is to get a short sliver of wood and make a marking stick with two drywall screws to measure the holes so they are the same distance apart – or at least closer than if I tried to lay them out with a tape measure on each board separately. The 5/8” poplar dowels at my local lumber mart looked really nice compared to all the other sizes. And 5/8 gives me an eighth inch on “either side” (if a cylinder may be said to have “sides” per say). Plenty of room for error though I think.

I really like the way the beam on horse trestles looks. I’m thinking about making a sliding dovetail planing stop across one or both ends of the beam/bench too. In the past I’ve just made wall benches with old 2 X 4’s and rough 3/4 or 1/2 inch ply held together with drywall or deck screws. Lately I’ve used my saw horses – they are made with old chicken barn 2 X 4’s and those really cheap flimsy metal horse jaws with a couple screws drilled in. So anything is an improvement.

The design of Japanese style trestle horses are very cool looking and I like the simplicity too. I’ll probably make the trestles from some KD doug-fir posts. I’d like to try my hand at mortise & tenon joints on those. I’ve done some really rough looking 1 X 1 MT connections on a spruce table that I made a long time ago. I’ll take a picture later (the table is sitting right in front of me, but my phone cord is in my car outside). So I know I can do it, but how well remains to be seen. I’ve been reading up on how to make better MT joints recently and I would like to get one of those Narex 1/2” mortising chisels soon. Otherwise I’ll hog out everything with a drill bit in my benchtop drill press (I’m not “unplugged” yet), and trim with bench chisels. It will be good to get some practice at it though.

Again, thanks much for your advice – I will take it! Really nice to be able to correspond “instantly” with experienced crafty folks all across the globe.

Cheers,
Rodney

-- Rodney, Arkansas

View djwong's profile

djwong

167 posts in 2682 days


#7 posted 02-15-2015 07:47 PM

Hi Rodney,

If you do use all-thread to clamp your boards, you should consider using thick cauls to sandwich the 2x boards you are gluing. Using the all-thread every 14” as you mentioned, may not provide adequate clamping pressure between the clamp points. Thick cauls will help to distribute the clamping force more evenly.

An alternative to all-thread is to use wedges to clamp the boards together. Make a series of wedge clamps each using a couple of 2×4’s with 2 pieces of wood or pipe for a wedge stop on either end. Use two wedges on one end to apply pressure.

Here is a screenshot from American Woodworker mag, illustrating the concept.

-- David W. Cupertino, CA

View nailbanger2's profile

nailbanger2

1041 posts in 2605 days


#8 posted 02-15-2015 08:07 PM

Thanks, djwong, for the illustration. That is exactly how I clamped the sailfish on the wall in my projects. It works very well, and is certainly cheap.

-- Wish I were Norm's Nephew

View ruddhess's profile

ruddhess

117 posts in 672 days


#9 posted 02-16-2015 02:32 AM

djwong,

Thanks for the illustration! I really like the Figure 3 clamp.
I am using bolts first (6 pairs of boards glued up with 3/8” X 3-1/2” bolts/fender washers/nuts). I glued the first pair last night and the remaining 5 pairs today. It was 50°F in my detached garage today, so I forged ahead. I even glued up the first quad using 3/8” X 6-1/2” bolts, etc. I ran out of Elmer’s wood glue and went to the store and ended up getting Titebond II (they were out of the bigger bottles of Elmer’s). BTW, I like the Titebond better – it seems to be easier to apply, doesn’t want to run as bad (thought that might be because I’m getting better at estimating the exact amount to put on each side), and it seems to clean up easier. Everything seems to be working well enough so far. I read somewhere recently where a dude tested his glue-ups and found out that beyond 6 or 7 inches clamping spacing (I don’t remember the exact number, but it was very close to one of those numbers) the glue didn’t stand up to “the test” – in other words was weak enough to break at those places. Now that I’ve spent so much money (well, not that much really) on Bolts/washers/nuts, I keep thinking – should have just gotten a couple more clamps. Pipe clamps don’t have the “reach” that I want on these ripped 2 X 10s (4-1/2 to 4-5/8 inches) – so you have to put a bunch of them on the top and a bunch of them on the bottom – that adds up quickly. So there probably are 4 places on each join that is weaker than the rest, but I think it will hold for quite a while. I am basically making a big board out of a bunch of little boards (which is kind of weird – I paid good money for a company to saw up really nice big logs and I even paid extra to a retailer to warehouse the items and market them and sell them to me – so I could buy a bunch of equipment and tools to put it all back together again – ha!) So even though I don’t want my work to fall apart – the main goal is to slap something together so I have a nice heavy, solid, and flat place to work on. Having worked at a small local steel tank and stack manufacturer, I keep envisioning big I-beam jigs with hydraulic presses to glue up my boards! I know there are probably others out there who have actually done this. That would cost quite a bit though. I don’t even know what steel is going for per pound anymore. But now we’re talking manufacturing design, not hobbyist/craftsman design. One thing I have noticed is that the all-thread seems to be a tad smaller than the threads on the hex bolts – a bit sloppy. In fact, I bought twice as many nuts so I could double up on them when I glued up the final assembly. I have a tendency to over-engineer stuff. Pipe clamps and the really heavy bar clamps seem sturdy enough, but I really don’t like any plastic in my clamps. I’m envisioning some rather stout heavy/duty lumber with some steel fasteners when I make one of those wedge clamps. I considered using sisal rope winding on my boards at first (similar to something I saw being used in a Japanese woodworking illustration or video – I can’t remember where I saw it) – though I think the work was much smaller than what I am doing. Also it seemed to me that the force applied by the ropes wasn’t going to be applied as efficiently as the clamps or the bolts would be. Hope that makes sense. Though I think the rope and wedge on a structural/architectural vertical beam would be an effective means to hold stuff down to work on it, or to hold something together to let glue cure. I have been thinking about incorporating wedged tenons when I make my horses for the beam to lay on. Thanks for listening to my ramblings. I like to think about and talk about stuff almost as much as I like doing it! :-)
Cheers,

-- Rodney, Arkansas

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ruddhess

117 posts in 672 days


#10 posted 02-16-2015 02:49 AM

djwong,

Now that I think about it – If a guy wrapped sisal rope (or similar non-stretch rope) around the beams (say 5 or 6 times around) and secured it – say do this at intervals with separate ropes. Then insert wedges on the outside edges under the ropes – thus putting pressure (possibly a lot) on the laminations being glued. This would probably take some practice to get it right, but I think it would work. And cauls would be necessary in this case for sure. (I’m doing the whole Robinson Crusoe island thing here.) But you could make cauls using only lumber and ropes too if you absolutely had to. Now you’ve got me to thinking about wedge design. Some people might say – it’s a wedge, what’s to design? – but too thin or too thick of a wedge would not work as well as that ‘just right’ angle of wedge.

Cheers,

-- Rodney, Arkansas

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ruddhess

117 posts in 672 days


#11 posted 02-16-2015 03:08 AM

djwong,

Also I have been thinking lately about the whole wound/twisted rope tightening type of clamp – like the way some bow saws are kept in tension. Just thought I’d throw that out there too. I used to help my dad fix fence when I was growing up – and I remember him twisting the wire on the corners to really cinch down everything. I’ll bet there are a lot of old type ways of doing stuff that most people haven’t even thought of. I have a couple of those wooden hand screw clamps that I really like. If a guy could get a left hand thread tap/die – those would be easy to make. I’ve never used or been around wood screws, so I don’t have any confidence in their durability – though rationally if good wood is used, there isn’t a reason to avoid making of using them. They are cool looking though.

Cheers,

-- Rodney, Arkansas

View djwong's profile

djwong

167 posts in 2682 days


#12 posted 02-16-2015 06:16 AM

Hi Rodney,

I think the “whole Robinson Crusoe island thing” is great. After all, it is all problem solving and clever solutions, and isn’t that what having hobbies are all about? Every chooses there entry point into the hobby.

P.s. Checkout thecarpentryway.com website, for some inspirational japanese woodworking. Lots of useful information as well.

-- David W. Cupertino, CA

View ruddhess's profile

ruddhess

117 posts in 672 days


#13 posted 02-17-2015 02:19 AM

David,

Problem solving, yes. And curiosity about traditional ways of working wood in different cultures! :)

Thanks for the link to that website – very interesting. Those gate joins are very complex! I have not even done a dovetail join yet! But it is fun to think about how to join wooden things together. I like a lot of Japanese stuff, and this is just another one!

I have taken quite a few pictures of my slab progress. I started putting some of them on my “blog” here on LJ. I am going to try and update the progress over there.

Cheers,

-- Rodney, Arkansas

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