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In my first large scale table I edge glued 7 quartersawn maple boards for a trestle table, 7/8 inch thick. The wood is dry and the cupping of the top is due to bad clamping technique by yours truly. The top is about 32 inches across and 6 feet long, and the two sides are about 1/4 inch higher than the middle. I could flip the top so it is a crown but would prefer not to. The top will be attached with screws in elongated slots in the rails.
Things I've considered: proceed with finishing, use force to hold it flat when a attaching screws. Cutting some saw kerfs in bottom and doing the above, going to cabinet shop with wide sander (would lose more thickness than I'd like), ripping top down middle and trying to correct it, adding breadboard ends (Not sure if tongue is strong enough to flatten.
Thoughts? Experience? Thanks in advance! Can add pics if it helps
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(02-25-2018, 09:14 AM)exatp Wrote: In my first large scale table I edge glued 7 quartersawn maple boards for a trestle table, 7/8 inch thick. The wood is dry and the cupping of the top is due to bad clamping technique by yours truly. The top is about 32 inches across and 6 feet long, and the two sides are about 1/4 inch higher than the middle. I could flip the top so it is a crown but would prefer not to. The top will be attached with screws in elongated slots in the rails.
Things I've considered: proceed with finishing, use force to hold it flat when a attaching screws. Cutting some saw kerfs in bottom and doing the above, going to cabinet shop with wide sander (would lose more thickness than I'd like), ripping top down middle and trying to correct it, adding breadboard ends (Not sure if tongue is strong enough to flatten.
Thoughts? Experience? Thanks in advance! Can add pics if it helps
Rip it at the joints (all of them) and re-glue it. It will never be right if you don't and none of your proposed fixes have a very high likelihood of long term success.
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1/4” is substantial. Without seeing it, I’d probably rip it down and do it over as well. I’d make sure your stock is flat and processed. Dry and acclimated too. If it doesn’t rest flat with the boards edged to one another, or dry clamped, you will be fighting it.
Try using biscuits or dowels to help alignment with the glue up. Use a slower setting glue, clamping cauls, and glue up smaller sections instead of one large glue up. Make sure each section is flat before adding them together. Enlist a helper for the glue up if needed.
Having each section or the whole top ran through a wide belt sander would be optimal. I had (3) 15” sections of a table top ran through a wide belt sander before one big glue up. It made a really big difference.
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(02-25-2018, 09:23 AM)jlanciani Wrote: Rip it at the joints (all of them) and re-glue it. It will never be right if you don't and none of your proposed fixes have a very high likelihood of long term success.
This. OP will loose some width but this is what I would do also.
Steve
Mo.
I miss the days of using my dinghy with a girlfriend too. Zack Butler-4/18/24
The Revos apparently are designed to clamp railroad ties and pull together horrifically prepared joints
WaterlooMark 02/9/2020
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(02-25-2018, 11:38 AM)Stwood_ Wrote: This. OP will loose some width but this is what I would do also.
Yep. You'll never be happy with it if you don't.
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Quote:Rip it at the joints (all of them) and re-glue it.
While this is the proper way to fix this issue ... as stated above you will lose 3/4"+ in width in doing so.
Assuming an 1/8" kerf and six joints ... more if jointing is needed to remove saw marks.
Perhaps you might get lucky enough that by starting with the outer two joints ... ripping/jointing ... checking for flat ...
that you might not have to rip all 6 joints.
Living outside the box I am.
~Dan.
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yep! Rip it apart & run your edges thru a jointer. As mentioned, dependin' on acclimation, how straight your boards are, & moisture content, glue ups can drive ya to drinkin' if ya let'em.
Were it me, I'd plane every board to thickness. Insure every board has straight edges. If not, straighten them. This will have a major bearing in your glue up. Match edges & grain in a dry fit. Mark the edges that fit together the tightest & straightest. Then start your glue up with 2 or 3 boards at a time. Use a brush & make sure the full width of the edge is glue covered. Lay your first boards on a flat, smooth surface. Alot of times, I lay my glue up out on the bars of the bar clamps & lightly start applying pressure to the clamps. You just need enough pressure to get squeeze out between boards. To much pressure will cause cupping! Let it set, preferably over night, then glue a couple more boards, & so on til you get your width.
thats my take on it.
Sawdust703
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02-27-2018, 03:52 AM
(This post was last modified: 02-27-2018, 04:00 AM by BobW.)
Here's what I would do, assuming you have a planer and jointer:
1. Rip the panel into three sections.
2. Run each of the sections through the planer to flatten, starting with the concave side down. remove as little material as possible...hopefully you can end up with at least 3/4" thickness.
3. Square edges on the jointer
4. Glue up the three sections...this time using cauls. Use some dowels if you have one of those old-school centering dowel jigs. They're not needed for strength but are great for making sure your edges are aligned and don't slip.
Bob
