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post #1 of 43 Old 06-09-2019, 03:08 PM Thread Starter
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Table Top glue up.

Iím working on a large harvest table and getting ready to do the top.

The lumber is one and seven-eighths inches thick, 84Ē long, and the four boards will be 36Ē wide when glued up and then trimmed. Itís some kind of softwood, likely fir or pine.

I donít own a jointer, so to true up the edges Iíve used a sturdy pattern makerís bit in my router, with a straight edge. Iím getting clean, smooth results, but my straight edge might have a slight curve to it.

Iíve done two edges, and when I dry clamp them they flush right up through 60Ē of the middle, but the ends flare away from one another such that thereís a >5/64Ē gap on each end. Itís easy to pull that together with a clamp. Is that something to worry about? Can I just go ahead and count on the glue to hold that together for years and years (Yellow glue, probably Woodtite II)? Or do I really need to get more perfectly straight edges?
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post #2 of 43 Old 06-09-2019, 03:15 PM Thread Starter
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To put it another way, if I clamp two of the boards at one end, and put a second clamp at the center of the length, the far end has a gap slightly less than 1/8” (a 3/32” drill bit slides between them a little loose, but a 7/64” drill bit won’t fit between them at all).

SO a total curve of about 7/64” across 84.” Is that too much bend to just force together and hold with glue? Or am I good to go?

FWIW, here’s an older thread about joinery for the base, with some photos.

https://www.woodworkingtalk.com/f5/hardware-no-212203/

The top boards have been planed, but I’m trying to square up the edges for the glue-up.

Last edited by Dylan JC Buffum; 06-09-2019 at 03:23 PM.
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post #3 of 43 Old 06-09-2019, 03:38 PM
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somethin ain't straight .....

Look down the boards to see if you see a slight curve on one or the other, maybe both? No matter, a few swipes with a hand plane will remove the curve a each end and give you a straight board. Hand tools have their place and this one, BUT you keep the sole, the bottom of the plane, square with the face of the board. Keep mating them together to see how the gap is reduced.
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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)
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post #4 of 43 Old 06-09-2019, 04:23 PM Thread Starter
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Originally Posted by woodnthings View Post
Look down the boards to see if you see a slight curve on one or the other, maybe both? No matter, a few swipes with a hand plane will remove the curve a each end and give you a straight board. Hand tools have their place and this one, BUT you keep the sole, the bottom of the plane, square with the face of the board. Keep mating them together to see how the gap is reduced.
Itís a good suggestion. Iím not one of those guys whoís resistant to hand tools. In fact, before I thought of trying to use the pattern makerís bit, I hand planed two of the edges and got fairly close.

But I also know Iím not that good with hand planes. This is so close and I fear Iíd make it worse messing with it. But is is close enough, or do I have to get it better to ensure a long lasting glue joint?
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post #5 of 43 Old 06-09-2019, 05:03 PM
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If you can pull them together with clamp pressure then a spline or biscuits MIGHT be enough to ensure long term success. If you want to get them closer you could get a straighter straight edge or even using the straight edge you have you could create mirror image edges on the boards. Use a pattern bit with the straight edge on top of one of the boards and move the other board close enough to the first board so that the bit removes a whisker from each board....this will give you mirror images which even if not straight will meet with no gaps.
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post #6 of 43 Old 06-09-2019, 05:36 PM
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You can run a circular saw between the two boards following a straight edge, that will make an even gap the width of the kerf so there will be a tight fit when pushed together.

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

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post #7 of 43 Old 06-09-2019, 05:44 PM Thread Starter
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So the consensus is, ďno, donít just count on the clamps and glue to draw and hold these edges. Get a more perfect fit.Ē

The attached photo shows the size of the gap. One end is loosely clamped. The seam on the right and in the center show the gap (ignore the one on the left: a shadow makes it look a lot bigger than it is).

Anyhow, super easy to draw them together with clamps. But yíall think itís a bad idea?
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post #8 of 43 Old 06-09-2019, 06:03 PM
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You will need to get the joint closer than that. The amount of pressure needed to draw the joint together will be the amount of pressure that will be trying to pull the joint apart. It can cause the wood to split in the joint or elsewhere.
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post #9 of 43 Old 06-10-2019, 08:53 AM Thread Starter
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You will need to get the joint closer than that. The amount of pressure needed to draw the joint together will be the amount of pressure that will be trying to pull the joint apart. It can cause the wood to split in the joint or elsewhere.
Not the answer I wanted, but I guess it’s the answer I needed to hear. So maybe y’all can help me figure out the cause of the problem. I’m a baffled by what’s happening.

I did the first two edges using an 8’ x 1” square aluminum tube as a fence. I clamped it to the board at each end, and could tell there was a slight flex in the middle. But that should have resulted in a concave curve (cutting slightly deeper in the middle as the fence flexed away from the bearing on the pattern-maker’s bit). Instead, I have a convex curve, where the boards meet in the center but not at the ends.

For the second and third pairs of edges, I used the edge of a Formica countertop as my straight edge. This also generated a convex curve, which I find even more baffling. There’s obviously no flex to the countertop, so the curve must already exist. But I can’t find it. I ran a three-foot level along the edge of the counter which I know is perfectly straight, and there’s no gap to be found.

Here’s my best hypothesis. I don’t think either straight edge is the problem. The problem is that the boards are not actually perfectly flat, and the router is following the curve of the surface, and translating it to the edge. Does that make sense?

Since I don’t have a jointer, but I do have a planer, I milled both faces of these boards with the planer. I know that this creates a problem where if one face is curved or twisted, that curve gets transferred to the other face, creating two parallel but not flat faces.

So might that be the source of the problem? A slight curve or twist along the length of the face could translate to a convex curve on the edge, right?

But that also doesn’t make much sense, because I would then expect edges not to be perfectly perpendicular along the whole length, and that doesn’t seem to be the case. There they meet, they meet perfectly; where they don’t meet, they have a perfectly parallel gap, not one that tapers.

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post #10 of 43 Old 06-10-2019, 09:38 AM
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Originally Posted by Dylan JC Buffum View Post
Not the answer I wanted, but I guess itís the answer I needed to hear. So maybe yíall can help me figure out the cause of the problem. Iím a baffled by whatís happening.

I did the first two edges using an 8í x 1Ē square aluminum tube as a fence. I clamped it to the board at each end, and could tell there was a slight flex in the middle. But that should have resulted in a concave curve (cutting slightly deeper in the middle as the fence flexed away from the bearing on the pattern-makerís bit). Instead, I have a convex curve, where the boards meet in the center but not at the ends.

For the second and third pairs of edges, I used the edge of a Formica countertop as my straight edge. This also generated a convex curve, which I find even more baffling. Thereís obviously no flex to the countertop, so the curve must already exist. But I canít find it. I ran a three-foot level along the edge of the counter which I know is perfectly straight, and thereís no gap to be found.

Hereís my best hypothesis. I donít think either straight edge is the problem. The problem is that the boards are not actually perfectly flat, and the router is following the curve of the surface, and translating it to the edge. Does that make sense?

Since I donít have a jointer, but I do have a planer, I milled both faces of these boards with the planer. I know that this creates a problem where if one face is curved or twisted, that curve gets transferred to the other face, creating two parallel but not flat faces.

So might that be the source of the problem? A slight curve or twist along the length of the face could translate to a convex curve on the edge, right?

But that also doesnít make much sense, because I would then expect edges not to be perfectly perpendicular along the whole length, and that doesnít seem to be the case. There they meet, they meet perfectly; where they donít meet, they have a perfectly parallel gap, not one that tapers.
There are a number of different things you could do. You could try machining the edge again just taking off wood on the high places. The amount of pressure you would put on the router on a little trim would be much less and better able to be more accurate. Trying to machine the edge of a board with a router is just difficult. If you add pressure on some places and let off in others it varies the amount of wood that is coming off making the joint not quite straight. You also may think your straight edge is straight but in fact may be off a thirty second or so. Not enough to see but when mating two boards a little off shows up big time.

You could also true up the joint with a hand plane. Just work down the high places.

Another option would be to build a router table and set up a fence on that table which is offset a sixteenth or so to mimic a jointer.
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post #11 of 43 Old 06-10-2019, 11:47 AM
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Basically the thicker and wider the board, the more perfect the jointing must be. With big tops like this, you also have to be concerned about twists, which adds a whole 'nother layer of work to getting a top flat. This is something that can be corrected after the top is done, but if several boards are twisted, you will have a tough glue up and end up with a much less thick top after correcting and flattening.

Dialing in jointing is difficult at best without a hand plane. First determine if its one board or both that is bowed. This can be difficult by eye so I recommend a long straight edge like a 6' level.

You can clamp out a small (1/64 - 1/32") gap in the middle, but not the ends. In fact, a small gap in the middle is called a "sprung " joint and is a technique that is meant to keep the ends extra tight.

As to your question about the convex curves, I'd be very skeptical about your aluminum channel being perfectly straight. Usually a factory edge on plywood or MDF will suffice.

But be sure the boards are acclimated and not moving after milling.
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post #12 of 43 Old 06-10-2019, 01:21 PM Thread Starter
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Thanks for your useful suggestions. I did wonder about whether the wood has been moving. The lumber sat in an attic for decades, and then in a finished basement for several years. Now itís out in my entirely unconditioned shop for about 6 months, and itís been beastly humid lately. Maybe I need to set it aside or find a way to store it somewhere dry before I keep going? I planed it from 2 1/4Ē down to 1 7/8Ē just this weekend, so maybe that would be significant?

I went out a little while ago and did a little experiment. I put a push pin in the very tip of the corner on each end, and pulled a piece of string taut between them (thank you once again, to the marvelous clove hitch, for being one of the more useful things Iíve learned in the past ten years).

Interestingly, the edge of the board on the far right showed a clear, even arc of about 1/8Ē across the full length. Thatís the one I did the with aluminum tube.

The two edges in the center seam, however, appear to be arrow straight. Those are the last two I did, and I used the Formica countertop as the straight edge. I havenít checked the bottom edges yet, so there might be a problem there.

As to the left seam, the leftmost board has a detectable twist. Iím not sure how to resolve that. I have another board I could substitute in which may be flatter. Iíll take a look.

Meanwhile, Iíll start with Steveís suggestion and just do another, very light pass using the Formica countertop and see if that canít close the gap.
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post #13 of 43 Old 06-10-2019, 02:41 PM
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It's also entirely possible the countertop is a little crooked. It's not intended to be that accurate.

If you had an actual jointer if the board was bowed inward in the middle you would position the middle of the board over the cutter and trim the wood to the end. Then turn the board 180 degrees and do the same. You might have to do something similar with your jointer. Set up the straight edge to slightly cut the wood on the end and nothing in the middle.
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post #14 of 43 Old 06-10-2019, 05:52 PM
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I'm in the fix it with a handplane camp but there's always another way.......

If you have a decent router bit that can cut the full depth (maybe even the pattern bit your using , then you can cut two boards at once that will fit together even if the joint is not straight. First straighten each board as you've been doing. Lets say your bit is 1/2 inch diameter. You then set the boards side by side, lined up well on the ends and sitting flat on cauls. Use a 3/8 spacer to create a space between the two boards, then run your router (off the straightedge) down the center of the gap. It will take off 1/16th from each side and they will mate even if not straight. You might have to change the gap if its way off or if your bit is a different diameter, just be sure to take something off of each board. Also take a notch out of the cauls so the bit does not hit. Countertop people do this a lot for long 45 degree joints or joining solid surfaces in showers etc.
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post #15 of 43 Old 06-10-2019, 07:03 PM
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Same concept, different tool .....

I would prefer using a circular saw with a full kerf blade and split the gap of the butted and clamped down boards. Do not clamp them together, just leave a slight gap. A straight edge may be used or if your circ sawing saws are good, not necessary.

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 #16 of 43 Old 06-10-2019, 09:14 PM
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I have done that and it worked really well.
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post #17 of 43 Old 06-10-2019, 09:33 PM Thread Starter
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I'm in the fix it with a handplane camp but there's always another way.......

If you have a decent router bit that can cut the full depth (maybe even the pattern bit your using , then you can cut two boards at once that will fit together even if the joint is not straight. First straighten each board as you've been doing. Lets say your bit is 1/2 inch diameter. You then set the boards side by side, lined up well on the ends and sitting flat on cauls. Use a 3/8 spacer to create a space between the two boards, then run your router (off the straightedge) down the center of the gap. It will take off 1/16th from each side and they will mate even if not straight. You might have to change the gap if its way off or if your bit is a different diameter, just be sure to take something off of each board. Also take a notch out of the cauls so the bit does not hit. Countertop people do this a lot for long 45 degree joints or joining solid surfaces in showers etc.
I liked this idea. A circular saw isn’t the best choice for me because mine is a cheap-o with a crappy blade, and I won’t get clean surfaces to mate.

Here’s the set up I came up with. What do y’all think?

I clamped the two boards down to the work surface, but propped up on 2x4s so the router bit won’t groove the workbench. I used the brass 5/8” collet to set the gap between the two at each end. Then I used the collet inserted in the router base to set the aluminum fence at each end. Finally, I braced the aluminum fence in the center with a scrap of 2x4. (Ignore the steel angle iron attached to the aluminum fence—that’s not in the way and it’s there for other uses of the fence).

The router bit is 3/4” cutting diameter. So it should take about 1/16” off each side.

I have two concerns.

(1) Because the boards are only clamped on the outside edges, there’s a very slight tendency to lift in the center. I figure I should be able to minimize that by pushing the router down firmly, and clean it up later with the pattern-maker’s bit in a router table, using the edge of the board itself as the guide.

(2) Because the fence is only on one side, I’m worried about the router’s propensity to run. I’m unclear which direction I should go to avoid having the router drift away from the fence and gouge the opposite board.

(3) Any other worries y’all see about this set up before I pull the trigger?

I’ll probably do a test run on a couple of scraps and see how it goes.
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post #18 of 43 Old 06-10-2019, 10:01 PM
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Hold the router pushed against the fence and move from left to right. i.e. toward the camera location that is taking the picture. Because you are not using a bearing guided router bit don't rotate the router in case the bit is not dead center in the base.
Did you consider using a glue line rip blade on your table saw?
Or making a guide from a long piece of plywood or hardboard with an edge guide. Glue/screw the edge guide to the plywood or hardboard and the run the router along the plywood with the router pressed against the edge guide to create a straight edge on the plywood or hardboard. Then lay the plywood/hardboard on your board and run the router along it, keeping the router pressed against the guide, to create a matching straight edge on the board. You can buy these but they are very easy to make and foolproof. This type of jig is very common for ripping plywood sheets to exact width with a straight edge using a circular saw or router.



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post #19 of 43 Old 06-10-2019, 10:30 PM
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post #20 of 43 Old 06-10-2019, 11:33 PM
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Do your best to make each board flat to the other before routing. If after routing its not flat enough you can use a top bearing flush trim bit to correct for square, but I think you'll be fine . You be the judge. Yes, push towards the camera when you route. That's why it's important to take a minimal amount off of each side as the stress on the router and bit is minimized. Yea, you'll need to focus hard on keeping the same point of the router base against the fence, but it's not that difficult when you are taking off so little.

Its a process, leave all parts a bit oversized and then you get a second chance. Sounds to me that you are paying attention to the important things straight, flat and square, so I know you'll get this right, Good luck
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