My first guess is that the space that is there now may well have been the cause of the glue failure in the first place. Of course, that's hard to tell, but could be.

Did you do a dry run first? That should have showed up any potential spaces in those boards.

 

I would have cut off the tongues as precisely as possible, then routed a groove on each side of the board, then cut a spline to fit the groove, then glued them up with clamps and cauls. If the tongue is cut with all boards face down on the table, the top should wind up flush and any sanding to level the underside up would be on the bottom, out of sight. The cutter for the groove would have cleaned out any glue, and you could make two passes to widen the groove slightly . With a trial fit, you could tell where the gap was, then use a hand plane to straighten out the piece(s) until it was a perfect fit, then glue. You would still have 99 percent of the full width when you were done.

 

BTW, you could still cut the pieces apart with a very straight rip cut down the line of the gap. Need to set such a cut up carefully and use a glue line type blade. Then you will have the same as a planed, straight edge that can be re-glued. Use a narrow kerf rip blade. I'd use my narrow kerf, Freud Glue Line blade for that after making certain my fence was a close as possible to parallel with the blade. And I'd double check with a Wixey digital gauge, to make sure the blade was exactly 90 to the table. You will likely lose about the same width with this approach as with a hand plane.

 

I think his question is more on why did this cut end up this way it did when the guide is stick straght, why didn't the cut mimic the clamp guide?

First, even if you push that saw tight against the clamp and know 100% for a fact it stayed super tight against the clamp the blade can wander. It wanders very, very little in these cases and most likely caused by the wood itself , either from an internal stress or grain characteristic that the blade just had to follow.

Second reason is near the first except the wood caused the saw itself to wander ever so slightly in the same manner and reason described for the blade. The saw left the clamp or the saw titled ever so slightly as you went from end to end.

This is why the track saw was developed. A track saw keeps the saw perfect straight and eliminates the saw from wandering due to wood stress or the saw leaving the edge of a guide. But I have seen blade wander even using a track saw, especially with a thin blade.

Also, unless a person is very skilled and the set up, saw, blade and wood(plywood is far better than hardwood) all perfect the method you used is never an ideal nor easy way to get two boards to line perfectly. The Bora clamp method is great for squaring things up, but joining or jointing two pieces calls for more precision than a setup like this offers. Still, if you used a track saw you would have had a far batter chance of getting good results.

One more thing, the wood could of actually moved after you cut it. Don't laugh, the stress in wood causes this all the time.. I make pieces that consist of geometric shapes and I cant cut the parts unless I know I can glue them up the same day for this very reason. The next day the pieces wont fit flush with a jointed like seam. The longer the parts are the more likely this can happen.

 

You only took a fine shaving off either side at the most and that shouldn't be enough to affect the boards tension. I'm not familiar with the Bora but it would need to be pretty stiff to eliminate that as a possibility and in fact, the problem occurred where it be most likely to if the straight edge were the problem. Its too bad you didn't find the problem before the glue up because it would have given you a chance to try to find the cause and fix it. Anything we can suggest is pure conjecture at this point.

 

Can you fill it in with a clear epoxy or resin?

 

Hey Mike, before I would repair the table top first I would want to know why the boards came apart in the first place. Look under the top to see if the top was screwed to the frame or apron in such a way as to prevent the top from expanding and contracting with the change in humidity. If that is the case your repairs will eventually fail.

As far as re-gluing the boards, I'd run the edge of the boards over the jointer to cut away the tongue and grove then put Tite Bond II glue on the boards and use pipe and or belt clamps to pull it together. I have repaired 4' round tables this way. On one table the top had failed because there were lag bolts holding the top to the frame preventing the top from expanding and contrasting.

Malcolm / Kentucky USA

 

Thanks for all of the suggestions and comments. Let me reiterate that the only power tool involved was a router with a straight bit. I don't have a track saw, jointer, or table saw. Only the width of a tongue was routed off of each of two boards. When I did a dry fit, it wasn't perfect, but it was good.

It's not important for me to go back and do any more work on this table. It's serving as a learning experience so that I can hopefully understand what I'm doing when it does matter.

 

Mike

A couple of possibilities; first, is the clamp actually straight - do you have a true straight edge for checking it
Second, it is possible that the clamp flexed in the middle when you applied pressure to the clamping mechanism.

 

Both are possible, but I have not been able to prove either one. No, I don't have a true straight edge, like a Woodpecker, but I have a lot of straight edges. I'll do some testing with the clamp today. It seems impossible to me for the clamp to flex because of its design. However, it's possible. clearly I don't know what the problem is. What is good is that the edge that I routed most aggressively is the one that fits best. I have to learn not to be afraid of the wood.

 

I misread the post about a router only being used, I knew you had no track saw, still riding router against an edge freehand isn't the ideal way to do it( i did it so many times back in the day with mishaps). Bora sells an attachment for some off their clamps to firmly attach a router that would have been better.

If you truly only touched the tongue the clamp being bowed cant be the issue, but that is a problem. You would have have been better served taking a hair off both sides down the entire length of the boards to ensure a nice flat, square straght cut, with a consistent fresh edge all the way down. Most likely where you cut the tongues the cut was perfect, the rest not so much. Leaving areas that were only scraped of adhesive and fresh cutting the tongue parts could possibly be an issue for glue up. We can't ever do a glue up on a joint where part of the edge is fresh cut and some of the edge isn't, that may be why this happened, either from uneven adhesive absorption rates along the edge or you simply thought the fit was perfect and it wasn't.

I use Titebond III for things like this and I have hidden gaps up 1/32 with it when clamping, something Titebond II and most other adhesives of this type simply cant do., I think if you used a different adhesive and the gap was very slight the adhesive could of hidden it.

The problem with one off operations like this is that we will never know why it happened for sure because you wont be doing it again to sort it out. I am sure it looks great as is, we tend to be to critical of our own work. The wife and friends probably don't even notice it nor care.

 

I think you have figured it out. It looks like I only routed the tongues on the bowed edges. Duh. Thanks for your critical thinking!

So Titebond III fills joints? I've struggled with which one to use, so I've purchased regular Titebond and Titebond II. Now I have to get a bottle of III. Live and learn.

 

L.V. 202GF glue

The Lee Valley 202GF glue works for this. The "GF" stands for gap filling.

 

Titebond has a chart on their website that shows the solids content in the 3 Titebond glues as well as open times, strength, etc. The higher the solids content the better it fills gaps. It's much like adding fillers to epoxy. The LV 202GF glue is every bit as good as the Titebond. I've used it before but you do need to keep the solids stirred up which you probably should do with the Titebond too.

Titebonds claim of waterproofness is nothing more than a sales gimmick, one that they've been very successful with. If you need a glue to be that waterproof you should probably be using mechanical fasteners to hold it together instead of glue.

 

I beg to differ about the waterproofing for the Titebond III.

The claims about the adhesive are not over stated in anyway.

I have tested Titebond III extensively as I must be sure my work used in exterior boat and ship decks won't fail. In 15 years I have had ZERO failures of the Titebond III being used in a boat deck application. It's waterproof for it's intended uses.

I also disagree about a mechanical fastener. Take two 12" by 12" wood pieces and use 20 screws to keep them together. I will pry it apart with a chisel dry, get that thing wet and a week later those screws will be failing, the wood will shrink away, the fasteners fail. All a screw is good for is to act as a clamp until the adhesive dries. The same two 12" pieces of wood glued together with Titebond III is simply impossible to pry or tear apart. I have tested this and the only way is to literally drum sand one board off . I actually have picture somewhere a subcontractor tried to get one of my marine ply backers off that was attached to hardwood using Titebond III in a vacuum press, they failed miserably. And this was after the thing sat in the wet weather for a month. They had to send it back for me to toss through the 50" drum sander.

The Titebond III has stood up in exterior deck work in the Chicago area. 10 years ago I edge glued joints with Titebond III, they are still holding and have no separation to this day. I have boiled two parts glued together, baked them in an oven and boiled them again, no failure. I have left pieces outside for so many years I lost count, and the parts are still holding. If this adhesive fails, it was either not used correctly, possibly someone had a bad batch or didn't mix it right, it has always stood up to water for me. It isn't for gluing the hull of a boat together, but for joining parts that get wet and not constantly submerged it's a dream adhesive.

Titebond III is far stronger than any mechanical fastener if the point is to stick two things together. It's not for structural use, but then again only certain screws of certain material and sizes are structural.. And woodworking screws aren't generally structural anyhow. Screws of course have their uses, but when adhesive is appropriate for the application it is is always better than a screw.

To stick two things together in an area outside with excessive water Titebond III has worked just as well as the West System Epoxy. Its characteristics are far better than any polyurethane adhesive and simply stated Titebond III is the best all around simple to use adhesive in the world.

I can only go by my life experiences. I go through 100's of gallon of West Systems epoxy and Titebond III a year and both work as advertised, no Gimmicks.

 

I don't suppose a pic of the area would help? I have a couple very old 2' and 4' straight edge clamp bars and an interlocking set extending to 8'; I can say that all but the interlocking bars have slipped at some point in a milling process. The interlocking set uses "C" clamps to fix the ends of the bar in place. When my clamps have slipped it was due to excessive pressure against the bar during the milling process and the resulting cut was not symmetric. To date I've never had any of the 2' and 4' clamps flex in the middle.

However, when I joined the boards, the outside edges were flush, but there is still a tiny gap in the center of the table.

If I understand and interpret Patlaw correctly then flush at the ends = tight joint not uneven joint. Tiny gap in the center = sides do not touch? How tiny is the gap and how long? Without seeing and if no one has already suggested, it sounds like a spring joint to me, intentional or not. I'd try to verify the accuracy of the bar with something else like a 4' aluminum straight edge measuring stick or 4, 6 or 8' stabile level. Even a tight weave line stretched taut over the length of either side would show a bend in the clamp by eye or feeler gauge.

 

I've not heard of those being called bora clamps but I have a set and hate them. They are very hard to get to clamp tightly. The problem is the cams have a very short range of motion and you have to get them really tight before pushing down on the lever.

I use pipe clamps and cauls instead.

 

I agree,Phil,I invested in a couple a few years ago and after the first few tries, I gave up and went to the boards and clamp or the saw guide I used for cutting bottoms off doors.
Herb

 

Dovetail you somewhat missed my point. Rarely do most woodworkers need a glue that is water proof. But many buy that glue because of the water proof claim. Any wood that is in a wet enough environment will cause other problems that are more worrisome than whether the glue will hold. A number of the outdoor projects that I've made failed beside the glue line. The glue was still holding, there was just no more wood for it to hold to and that includes using Resourcinol. I am of the opinion that the glue may have held water at the joint which caused the wood to deteriorate faster. I have way better success using mechanical fasteners as the fasterners (bolts as much as possible) allow movement without weakening the joint and don't contribute to joint failure as I suspect the glue might.

 

What you are talking about is the wood around the glue expanding and contracting, weathering, this to me is not a glue problem ,but a finish problem, The finish on the wood is such that it is not keeping moisture out and the wood is swelling and shrinking to the point of causing the joint to fail. this also happens to cause glue joints to fail if the glue is not waterproof, but if the glue is not failing and the wood is, then thats a different situatiion. Oil and Epoxy are the only clear finish I have seen that holds up in a wet climate. All the others I've seen gets black spots under the finish and start to blister and peel.

Herb

 

excellent points Charles...

 

Where I live, surely we are a weather testing ground, we get the wind, rain, sun, cold, salt and snow in all combinations. I've done outside work, furniture repair, molding and column restoration, flower boxes, trellises and arbors etc., inland and on the coast. I can attest that the only glue that has stood the test of time along the coast is Gorilla Glue Poly. TBII & III even with biscuits, has come/pulled apart within 2 yrs, more often inside of 12 months, (I glue biscuits into the holes too, not just for alignment sake). I tried Gorilla glue because I got tired of call backs. I like the TB line, (I use it for all indoor projects and if customers maintained their property TB would probably last longer outside around here. I particularly like the TB trim/molding glue, and use it a lot especially for small projects.