Can you fix a breadboard?

[FS7]

My guess is no, but I wanted to ask.

I made a top for one of my pieces and let it sit for a while until I could get to the rest of it. It's about 18" wide, mostly sapele with bloodwood and maple accents. It was pretty flat (not perfectly) and finished evenly on both sides.

During initial glue up, there was apparently some spring in the boards, and I had gaps at both ends. To fix this, I cut off the part that wasn't glued and added breadboard ends to both sides (I still wanted the width). I used the Domino, which in hindsight may not have been the best idea. Maybe it was fine and the tenons were just too small (it's about a 3/4 top, and I used the standard 5  mm tenons.

What I believe happened is that the top wanted to cup and the 5 mm tenons were too thin, too short, or both, and one side actually snapped the tenon (or angled it, I'm not sure). Expansion/contraction looks to be allowed normally, but cupping caused a huge problem. The sapele end did not warp, but the top did, so there's a noticeable gap at one end where the tenon sheared or bent. Unlike typical breadboard differences (part of using wood, as it were), this is an obvious flaw.

It looks to me like I will need to rip the ends off and use larger tenons - I have the 8x50 tenons, which are about three to four times the size of the  originals. I can use more as well.

The other alternative is to redo the top and use the existing piece (which is about 54" long without the ends) for two nightstands, which are also on my list.

[hbmcc]

At 54-inches I don't think you are slicing bread. 

Without checking the expansion properties of your wood, my WAG is there is a good bit of variation between the species; a red flag. Also, much of the wood I see has not had nearly enough time to dry, kiln or air. Finally, the purpose of breadboard ends is to allow the intervening field to swell and shrink freely in a laterally controlled manor. They are loose mortises and tenons, outside the one you want fixed which is three to four inches of glue. Warping can be managed if mild mannered, but don't rely on that tongue and groove clamp to fix a problem.

I know nothing about biscuits other than eating some varieties after attempting to slice my fingers off.

[AHill]

I call what you made a pastry board rather than a breadboard. I've made a couple and always used 1/2" maple with breadboard ends. I used Dominos both to align the boards before I glued them up and to attach the breadboard ends. The ones I made were 30" wide x 48" long. Yes, that's a big panel. Breadboard ends cannot guarantee preventing cupping or twisting of your panel. Increasing the size of the tenons probably isn't going to help, because the tenons only provide the connection to the breadboard ends. I personally think you need to start over or salvage what you have for another project. The key is to make sure the panel is flat during glue up and also joint, pre-fit, and adjust the the boards in the panel prior to glueup. Getting large panels flat takes some stable wood and a lot of care to joint and during glue up to prevent warping, twisting, or cupping.

[FS7]

I didn't know "breadboard" was a thing. I meant breadboard ends on a table top, or what is effectively a table top. It's a large panel, about 18" x 54" without the ends.

I know breadboard ends don't prevent cupping of the top. I thought, however, that a 1x3 sapele board used for the end would bend slightly as the top cupped. However, the top cupped, the sapele didn't budge, and as such the weak point, the tenon, must have given out. My guess is that thicker (and deeper) tenons, and possibly more of them, would help prevent cupping (or at least tenon failure). Stress is fine, but not failure. 

I don't think the different species have anything to do with it. The top is mostly (85% or so) sapele, and the ends are sapele.

[rwe2156]

He is talking about breadboard ends, not a cutting board.

Sounds like something wasn't right from the start with the glue up, but there could be some tension in the boards.

More likely the wood wasn't acclimated. I say this because the wood moved enough to break a domino. You have to allow for movement when you do a breadboard end. The traditional way is to use draw bored pins and over sized holes in the tenons. This allows the top to move laterally while the BB end stays in place. You do not every use glue other than the middle tenon this defeats the purpose of allowing the tenons to float.

Based on what you said I think you should rip the top apart along the glue lines, sticker the boards for a week or so, and re-joint/replane if any cupping that has occurred. It sounds radical but it is the best solution to a problem like this. When you do it, pay really close attention to the grain direction on the faces as well as the ends. The more curved the rings (center of the tree), the more a board will cup when it dries.

IMO the best way to do breadboards is to make one large tenon on the end that is drawn bore pinned (no glue).

I never use a bb as preventive to cupping. It simply won't work unless you use a very thick board as your end.

[FS7]

He is talking about breadboard ends, not a cutting board.

Sounds like something wasn't right from the start with the glue up, but there could be some tension in the boards.

More likely the wood wasn't acclimated.  I say this because the wood moved enough to break a domino.  You have to allow for movement when you do a breadboard end.  The traditional way is to use draw bored pins and over sized holes in the tenons.  This allows the top to move laterally while the BB end stays in place.  You do not every use glue other than the middle tenon this defeats the purpose of allowing the tenons to float.

Based on what you said I think you should rip the top apart along the glue lines, sticker the boards for a week or so, and re-joint/replane if any cupping that has occurred.  It sounds radical but it is the best solution to a problem like this.  When you do it, pay really close attention to the grain direction on the faces as well as the ends.  The more curved the rings (center of the tree), the more a board will cup when it dries.

IMO the best way to do breadboards is to make one large tenon on the end that is drawn bore pinned (no glue).

I never use a bb as preventive to cupping.  It simply won't work unless you use a very thick board as your end.

The glue up wasn't perfect. Because of my shop limitations, I was only able to plane the center (about 12") of the panel. This was about 8-9" of sapele, with the bloodwood and maple on the outsides. I then used the tenons and glue to attach the other two sapele boards, but without a drum sander I have slightly less confidence in the panel being uniform. I know a planer won't flatten a board, but it does help and I feel like a drum sander would have made sure the panel was completely flat. It was still pretty flat and didn't rock or anything, but it may have been slightly off. I can't actually say for sure. I almost certainly didn't pay attention to the orientation of the rings.

I have done regular breadboard ends, with a full-width tongue and a corresponding groove with drawbored pins. That was on a much thicker top (about 6/4 to start). I wanted to try using the Domino for this, so what I did was put a bunch of tenons in the ends of the panel (three grouped in the center, zero clearance, glued on both sides) and a bunch on the rest of the panel. I don't remember the exact number. They were glued on the panel, while the breadboard end had elongated mortises (using the Domino's width settings) and no glue. In theory, this allows for lateral expansion and contraction, and it seems to do that. The problem is the panel cupping seems to have broken the tenon (don't know for sure).

If you mean re-ripping lengthwise, I doubt I'll do that. I might try redoing the end with bigger tenons, and if that doesn't work I'll scrap the idea and the use the panel for the two nightstands I thought of. I'm honestly not sure I like the design for the kitchen any longer anyway, and I did just buy a healthy stack of Goncalo Alves, so...