Failure Analysis Help

[Vaughn McMillan]

Some of you may recall seeing pics of a quilt patterned "cutting" board I made recently for a co-worker to give as a gift. Nicest (IMO) and most challenging cutting board I'd made to date. Not more than a three weeks after completion, the board has cracked badly. Fortunately, it failed before it was given as a gift, and I'm going to build a replacement post-haste. I'm looking for advice in order to avoid having the same problem happen with the replacement. First, the forensic evidence...

Here's the cracked section. You'll notice it not only broke along the glue joints, it broke one of the pieces of wood as well. You can see a bit of the 3/8" dowel in the widest part of the crack. (The frame of the board is glued and pinned with four dowels along each edge.) It's obvious something changed size, but I haven't figured out if something expanded, or if something else shrank.

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Here's the whole board, so you can see the various wood grain directions. The geometric part in the center of the board is all end grain, and the border is face grain. I believe therein lies the crux of the problem. Also, the final thickness of this board ended up at a bit over 1/2", which is quite a bit thinner than I wanted. I believe that was also a contributing factor, but I'm not sure. Regardless, the replacement board (and another like it that has already been ordered) will be at least twice that thick.

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The end grain materials had all been in my shop for at least a month before milling, and at least that long after milling before being glued up. The border wood was also wood I'd had on hand for a few months, but it was glued up shortly after milling, then attached to the end grain part a few days later.

Another anomoly is that I used plastic resin glue to assemble the nine individual inner square sections, then used Titebond II to glue the nine squares together and to attach the border. Even though the board felt as smooth as polished marble when I delivered it a couple of weeks ago, I notice that now I can clearly feel each of the Titebond joints, but the plastic resin joints are still "invisible" to the touch. I'm guessing this is what folks mean when they speak of glue "creep". It this a correct assumption?

I knew all along that I was taking a chance having different wood grain and shape orientations without making some allowance for wood movement. I was trying to avoid floating the center panel within the border, and instead making it a solid unit -- it's supposed to be a cutting board, after all. Do I need to resign myself to the reality that it'd never be used for actual cutting, so I might as well make the two disparate pieces flexible? If so, any suggestions on how? T&G or splines come to mind, but is there anything I'm missing here? Or will a 1" to 1.25" thickness handle the problem and allow it to be glued solid?Any suggestions are welcomed.

Thanks in advance -

- Vaughn

[Tim Sproul]

Or will a 1" to 1.25" thickness handle the problem and allow it to be glued solid?

The parts that show as endgrain are expanding. It looks from the first picture that the middle section expanded out to the right, causing the crack.

I'd suggest you're 'solution' is going the wrong direction. What you likely want to do to control movement is to cut the pieces thinner and apply them to a firm, stable substrate - MDF is a good choice - with a very rigid adhesive. Unibond or a plastic resin or epoxy come to mind. If you go the veneering route, you'll have to be mindful of the end grain having adhesive bleed through so a clear, rigid epoxy might be a good choice.

[Lee DeRaud]

The parts that show as endgrain are expanding. It looks from the first picture that the middle section expanded out to the right, causing the crack.

Second that...note that the end-grain chunk can/will move in both directions.

When did it happen, during the rain last weekend? Wonder what it's doing yesterday and today...

[Alan Turner]

Vaughan,
I think what you may be seeing are the results of why frame and panel construction was developed. That is, the middle pieces, which are endgrain, shrunk, but the long grain wood, on the bottom of the first picture, did not move end-to-end, which is to be expected. Thus, the endgrain wood split as it shrunk, since being glued on both sides it could not move freely with expansion and contraction. I think what you have is a design issue, and not a construction issue. The solution would be to eliminate all long grain. Stronger glue will not work.

If you look at a traditional end grain butcherblock, even though it is 8" thick or so, it has no long grain to restrain its movement.

My Dad retired to Arizona and became a more active woodworker. He used to like to build clocks of glued up wedges, 12 sided pies, sort of, which were then banded on the perimeter. They worked fine there, but in Philadelphia, they split apart badly. In California, you probably have less winter to sumnmer EMC change than in other parts of the country, but you still have some, it seems.

[Kirk (KC) Constable]

Another anomoly is that I used plastic resin glue to assemble the nine individual inner square sections, then used Titebond II to glue the nine squares together and to attach the border. Even though the board felt as smooth as polished marble when I delivered it a couple of weeks ago, I notice that now I can clearly feel each of the Titebond joints, but the plastic resin joints are still "invisible" to the touch. I'm guessing this is what folks mean when they speak of glue "creep". It this a correct assumption?


- Vaughn

Yes, exactamundo.

[scott spencer]

Hi Vaughn - I really don't have a definitive failsafe answer, but a substraight was the first thing that came to mind, and of course my Guinness alter-ego said "brilliant!", so that must be the correct answer.

[tod evans]

wood will move untill it turns to dust, period. if you do patterns and expect them to survive you must use veneer over a stable substraight. unless you are able to orient the grain concentricly using woods that have similar swell/shrink properties. you`ve just learned the single most important lesson when working solid wood.......02 tod

[Art Mulder]

You likely want to do to control movement is to cut the pieces thinner and apply them to a firm, stable substrate - MDF is a good choice - with a

Errr, Tim, I don't know about you, but I regularly dump my cutting boards into the sink and rinse them off. I may not submerse them, but I definitely run water over them. I can't forsee MDF performing well in a situation like that. Even if the MDF is covered all around, I still would expect dampness to get to it.


best,
...art

[tod evans]

if you`re looking for stable core material i recomend exterior grade baltic birch. a few years back i boiled a 3/4 thick 1x1 square in a coffee cup in the nuke every day for a month and it didn`t delaminate....oh-yeah, it lived in the water between boilings.......02 tod

[Art Mulder]

oh-yeah, it lived in the water between boilings.......02 tod

Tod.... next time, try taking it out of the mug every day and letting it dry. I'd be interested to hear if you get different results.

You see, I've been told that it is the wet-dry cycle that does in wood, not just being wet. Therefore, the posts that support a pier/dock... they don't rot where they are in the water, no, they fall apart at the water line.

[tod evans]

Tod.... next time, try taking it out of the mug every day and letting it dry. I'd be interested to hear if you get different results.

You see, I've been told that it is the wet-dry cycle that does in wood, not just being wet. Therefore, the posts that support a pier/dock... they don't rot where they are in the water, no, they fall apart at the water line.

never tried that? i was thrilled that it could survive what it did. figured it was stable for use on a conference table as a substraight which is what i used it for

[Mark Singer]

Either all end grain or a pattern where the cross grain expansion can occur without restraint of other members....there is no design for expansion as built.. This wet and dry season we are getting made it fail quickly...

[Vaughn McMillan]

Thanks all. Your comments align with my own suspicions.

The idea of making it as a veneer hadn't crossed my mind, although part of the "panache" of the piece is because it's solid wood, and I'm leaning towards keeping it that way. (What you say is too true, Tod. Hopefully, the lesson has been learned. )

I'm going to talk to my "customer" about her preferences Monday, but I'm leaning towards using a floating panel/frame construction. My only misgiving about that method will be the "seam" between the border and the center section. I like my boards to feel seamless. Even though it's doubtful this will ever be used for cutting, it might need to be washed with soap and water, and I can't see that as being good for a frame & panel piece.

I've also not ruled out going with an all end grain construction, but I suspect I'd need to break up the long sections of the border into smaller squares, due to the disparity in their dimensions compared to the other (smaller) pieces. I'm assuming if I make these pieces long (even as end grain), they will expand and contract at different rates than the smaller pieces. Is this a correct assumption?

Lastly, the failed board was finished by soaking it in mineral oil for about 48 hours, then wiping it "dry" with towels. I wonder if that might have contributed to the wood swelling as much as it did, and I'm thinking of going with some type of membrane finish on the next one, perhaps "salad bowl" finish. Any thoughts?

Thanks again -

- Vaughn

[Lee DeRaud]

I've also not ruled out going with an all end grain construction, but I suspect I'd need to break up the long sections of the border into smaller squares, due to the disparity in their dimensions compared to the other (smaller) pieces. I'm assuming if I make these pieces long (even as end grain), they will expand and contract at different rates than the smaller pieces. Is this a correct assumption?

Doesn't sound right: a given width of wood in a given orientation should move the same regardless of whether it's one piece or a glue-up. There may be some difference in movement due to the various species in the field vs the border, but that should be minor compared to orientation differences.

Just ask yourself, WWALD? ("What would Al Ladd do?")
Consider this: http://www.alladd.com/largemaplechoppingblock.htm

[Gregg Mason]

Vaughn, sorry it had to be at your expense, but this has been a good education for me. When I had first seen your board, I never thought about it being a problem. Also, you raised an interesting point about soaking it in the mineral oil. I could see that be a contributing factor as well. I hope it works out for you.

Gregg