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Discussion Starter · #1 ·
I am going to build a replacement top for a coffee table. The first picture shows the existing top which is 39” X 39”. It is a veneer on plywood. The edges are supported by a frame of some kind of composite. I will be replacing it with a walnut and maple top similar to the second picture, which I found on the internet.

The inside part of the table will be constructed by edge gluing 6 boards 5 ½” X 33”. I have never glued up a panel this large although I do have enough clamps to handle it. Hard to believe I actually have enough clamps for a project. That’s one in a row for me. Anyway, in the past I’ve used cauls to keep the boards flat while the glue dries. I’ve had relatively good success with this although on larger panels, along some of the joints, the boards would be a bit higher on one side of the joint and lower on the other which required sanding to even them out. I’d like to try to avoid as much of that as possible with the new table top although I know it won’t come out perfect and will require sanding.

As an alternative to cauls, I’ve seen some videos where, after the boards are clamped, they use face clamps to align the boards and pocket hole screws to secure it until the glue dries. Some people removed the screws after the glue dried so they could reuse them, some people left them in. I do have a pocket hole jig and screws. My question is, has anyone used this technique and what kind of success or failure was it? I will be using pocket hole screws to help secure the maple/walnut edges since two of those edges will be gluing edge grain to end grain.

As always, thanks for your help.
 

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I can’t help with the screw question. I rarely use them. If I really wanted the glue up flat on one face I’d either spline (blind grooves if they aren’t supposed to show at the ends) or dowel. You could make a quick and easy dowel jig using some ply and wood scraps along with Lee Valley drill bushings. The jig would look like a T with the bushings in the leg. With the cross registered on the show face the holes would all be equidistant and the same distance from the faces. As for gluing to the end grain I would keep adding glue until the end grain stayed wet before I stuck it to edge or face grain.
 

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If I understand you correctly, Barry, you want to 'breadboard' trim onto solid lumber panels(?) ... "I will be replacing it with a walnut and maple top" .
There are species specific expansion/shrinkage tables for lumber planks, and even for the relatively stable ones it's still significant. the sidetrim isn't an issue; very little longitudinal movement, but the end grain over three ft. would have significant movement.
Gluing the end trim might be a serious problem down the road if not immediately.
https://www.popularwoodworking.com/tricks/how-to-calculate-wood-shrinkage-and-expansion/
https://www.woodbin.com/calcs/shrinkulator/
Oh, and before Stick beats me to it, splines! :)
 

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Blind splines will allow you to glue up the pieces while leaving the ends unaffected. Splines for the long grain side. The trick is to flatten and thickness your stock BEFORE you cut the grooves for the spline. Flatten the top either with a hand plane or a planer. Cut all the grooves with the flattened face down. This will help greatly on producing a flat glue up. Do the flattening, cut the spline, glue up and clamp on the same day. Wood can warp enough to be annoying in one day. Be very careful in selecting your stock. Quartersawn is your best bet for this kind of project.

The grain of your splines should be cross grain, the grain should run perpendicular to the long pieces' grain. This means you will have to piece together the spline piece by piece. I'd thickness the spline material and match the grooves to the spline thickness so it's a snug fit. If you don't have a planer, you can use your table saw or band saw to resaw your spline pieces to the thickness you want. Then trim off short pieces for the spline. If you use your table saw to resaw, make sure your blade is exactly 90 degrees to the table. If you don't have a Wixey digital angle gauge, get one first. They're $30 on Amazon.

If the piece you're resawing for splines is 3/4, you can get two quarter inch wide pieces from each pass, and if the material is too wide to split in one pass, you can flip it over and resaw the other half. Try not to have the blade overlap the first cut on the second pass. This will allow you to cut at least a 5 inch wide board for splines.

You can use splines to attach a finished edge to the short ends. Make a nearly full length groove, but not all the way across, in other words, a blind groove. Remember, face side down on the router table, or face up if you're cutting the groove freehand. Place 3-4 splines here and there along the groove to allow a little freedom of movement for normal expansion and contraction.

You can use pocket screws to hold the table pieces in place during glue up, but put the screws in through bottom side and use a cawl to hold the pieces firm, finished face down as you pocket screw them together. Once glue is set, you can remove the screws and even fill the holes. But you really don't need then since you're using splines for alignment, and everything cut flat face down will align pretty well.

This method will allow you to get a very flat table top that will require only a minimal amount of sanding to level. Finally, I'd consider using a scraper for a final pass to smooth out the top. Nothing looks better than the effect of a good finish on a scraper prepared table top.

Again, I'd go with quarter sawn wood for the long pieces. It costs more, but will be easier to get a great result. BTW, if your stock is 3/4 inch, your spline should be about a quarter inch thick. I love splines. Easy, strong, invisible, although a through spline with a different color between equal width glued up material can really look nice. One nice thing about a solid wood top, you can put a beautiful edge on it.

Hope this is helpful.
 

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Discussion Starter · #5 · (Edited)
Wow, I’m glad I posted this. I’m such an idiot. I was going to do a future post questioning how to attach the base since it’s screwed down on all four sides (as you might be able to see in the picture, 20 screws is a bit of overkill) and I was concerned about wood movement. It never occurred to me that the bigger problem would be the edge to end grain over the 33”. I used the calculator in Dan’s link and, using some assumptions since I don’t have the lumber yet, I came up with ¼”. I will be finishing the table top with Extreme Protection Polyurethane from Crystalac. I don’t know how much this will reduce the movement but I know it sure won’t be 0.

As both Tom and Charles suggested I’ll use blind splines to align the boards. I have a slot cutter for my router and, as you stated, if I route all of the slots with the boards face down on the router table all of the slots will be the same distance from the top of the boards so they should align quite well. Since I’m using the spline for alignment not for strength, I can cut a spline the full length of the slot so that the grain going in the same direction won’t make a difference. However, for the frame on the end grain sides I’ll do as Tom suggested and cut the slot full length but use cross grain splines at intervals. Does this make sense to you?

Tom, I always do as you suggested about prepping the wood. I buy rough cut lumber from the yard let it acclimate to the shop for a week or two then mill is slightly larger than finished dimensions. I let it sit overnight then mill it to final dimensions and glue it up. I learned this lesson the hard way early on in my woodworking.

If I can ask you one more question since we’re on the topic it’s about attaching the base. First off, I’ll use two screws for each side not five. This is a coffee table and not built to withstand a nuclear attack. If I elongate the holes so that the elongation goes across the grain, and snug up but don’t firmly tighten the screws, do you think that will be enough to handle any expansion?

Once again, I want to thank you for your help. Without it, this project would have ended in disaster.
 

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Probably the simplist way is to use table top mounting brackets as shown in the picture. Cut a groove in the table frame and loosely attach the top with a short screw. There are other methods, but his one works great.
 

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Hi Barry,
I used your proposed method for a vanity slab some 12 years ago. Used polyurethane glue and pocket hole screws, nothing has moved in that time. My end-grain length was about half of yours, but nothing has moved there either (but I was able to leave a "free" end at the non-visible splashback end). Probably because the wood was very well-seasoned up-cycled floorboards of a species formerly known as Rhodesian Teak Rhodesia is now Zimbabwe) not a teak as such, but a hard, splintery wood, used for railway sleepers before concrete took over. Sands to a very smooth finish.
I used clamps and caulk as well, although probably overkill. Did not remove the screws out of laziness.
At the time, I was not equipped to make splines, at least not safely. But I have since become interested in spline joinery thanks to Stick, Tom and others here, and was took Tom’s advice to watch the Mark Sommerfeld videos on spline-based cabinet-making, so might well use them if I were doing the job now.
Although I followed Tom’s good side down rule, the piece still needed a fair amount of sanding and scraping.
I turned the legs from laminated sections of the same wood, and beat the copper basin out of 1mm copper sheet.
If you zoom in on the images, you will see the joints are all tight, in spite of noxious potions my adored wife might have spilt onto the surface.
 

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Although I followed Tom’s good side down rule, the piece still needed a fair amount of sanding and scraping.

it's good side up for free hand and good side down for the RT......
the splines do a great job of/for aligning for a flush surface...

.
 

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Discussion Starter · #11 ·
Tom, I’ve seen that before but, since my base is wrought iron I initially dismissed the idea. But somehow it stuck in the back of my mind, what’s left of it, and then the simple answer came to me. All I have to do is attach a wood frame to the top of the wrought iron, cut a groove all around it, and connect the top to the frame using those connectors. I’ve been mulling around how to do that for weeks. Thank you!

Biagio, that is an absolutely beautiful piece of work. Very well done. Did you turn the legs too? I’m not a turner but I can appreciate turned pieces having seen it done and the work that goes into it.

I’m now considering three ideas of how to join the 6 boards. First, the original idea of using pocket hole screws until the glue dries. Second, the popular idea here of using splines, which I will use to attach the edges to the end grain sides. And, a third way that I just thought of. How about tongue and groove? That’s how they make flooring. I’d have to buy the bits but, in the long run, would that be easier than cutting the grooves and all of the spline pieces, not to mention stronger? Oh, wait, I just mentioned stronger. Anyway, have any of you used tongue and groove joinery and if so, how difficult was it to get it right?

Stick, thanks for the info. I've read that before when you posted it for other members questions. I consider you the encyclopedia of RouterForums. Has anyone ever stumped you with a question?
 

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Barry; nothing wrong with T&G but you're over thinking this; glued splines are incredibly strong!
Way easier and no new tools to buy...OK, that may not be a selling point. :)
If you're doing blind splines, and no reason to if you're adding end trim, just use 1/4" plywood for your splines. Nobody will ever see them and grain direction is no longer an issue (for the splines, not the planks),
and if you're clamping the whole assembly anyway, why do you need the pocket screws?
Using the cawls is just the right thing to do; you don't want to introduce a bow into the assembly from the clamping pressure.
Just make the spline slots deep enough that there's plenty of glued surface...and make the slots a tich deeper than the ripped width of your splines! You don't want the splines to prevent the plank gap from fully closing
 

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And, a third way that I just thought of. How about tongue and groove? That’s how they make flooring.

Has anyone ever stumped you with a question?
the T&G joint is sized (sloppy) to allow for wood movement, it's shallow (¼'') and doesn't stayed glued up for long..

Stumped??? all the time...
 

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the T&G joint is sized (sloppy) to allow for wood movement, it's shallow (¼'') and doesn't stayed glued up for long..
no real strength either...
see...

.
 

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Biagio; that vanity is beautiful! I hate seeing wood around water but yours seems to be holding up extremely well. Great job!
Thanks, Dan. The piece was given multiple coats of polyurethane marine varnish on all surfaces, including the underside. The finish has laughed off water, but took some strain from nail polish remover, hair remover and other chemicals that women apply to themselves, but that we would hesitate to apply as paint strippers or rust removers.
My first wooden vanity was built in 1993. Imbuia - now a protected species, and costs the earth - at least around here. Simple edge-to-edge gluing, same polyurethane glue, same finish. I had not discovered cope-and-stick bits at the time, so the cabinet doors were made with routered M&T joints. At the time, I found some Imbuia-faced plywood for the panels. Made the tenons and mortises too deep, so that the tenons suddenly showed through when I undercut the lip for the doors.
Interestingly, the oil in the wood reacted with the marine varnish to form tiny bubbles, and because it was hot weather, the varnish started setting before the bubbles could break the surface. No amount of thining helped. After several sandings down and re-finishing, visits from supplier experts, etc, I just acceoted it as "hand-crafted slight flaws".
 

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I normally use the same fasteners that Tom showed but Lee Valley also sells elongated steel washers that will work. They are a Christian Becksvoort design. They allow movement between the head of the screw and the washer.
 
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Discussion Starter · #17 ·
Yep, you're all right. I'll go with splines the entire length and, Dan, you answered my next question which was, can I use 1/4" plywood for the spline The good thing about 1/4" plywood is that it's true to size, not undersized like thicker plywood. I ordered a 1/4" slot cutter this morning since the one I have for biscuits is the wrong size. I already have the arbor and various size bearings so I just need the cutter.

I also realized that attaching the top is much simpler than putting a frame over the wrought iron base. Adding the frame would also raise the table higher than we want it. The top of the base has a flange all around it. See the picture in post #5. All I have to do is screw what I call the Z shaped fastener to the table top in such a way that the bottom piece of the fastener, rather than going into a grove, goes under the flange. I may have to reshape the fasteners so that they are snug up to the bottom of the flange.

If anyone has any other suggestions please post them, otherwise I'm good to go as soon as I get the lumber. I have a call into the lumber yard to see if they've gotten a shipment of better quality walnut.

Again, thanks for everyone's help. I really would have screwed this up without you.
 
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on those plywood splines..
use Baltic Birch...
trust us on this one...
 

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s.
Interestingly, the oil in the wood reacted with the marine varnish to form tiny bubbles, and because it was hot weather, the varnish started setting before the bubbles could break the surface. No amount of thining helped. After several sandings down and re-finishing, visits from supplier experts, etc, I just acceoted it as "hand-crafted slight flaws".
next time...
use a scraper on the bubbles and not sandpaper...
 
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