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Cracked Tabletops

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Forum topic by jonross667 posted 01-27-2018 02:20 PM 1088 views 0 times favorited 47 replies Add to Favorites Watch
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jonross667

13 posts in 321 days


01-27-2018 02:20 PM

Topic tags/keywords: table top joint kregg jig poplar cracked split joining

Hello, Jon here, i’m new to woodworking. I haven’t had any training other than trial and error, and I’ve now had two of my poplar table tops crack. They were built around the same time and I used the same methods for both. I found some plans online to work off. Both tables have cracked lengthwise with the grain. Both tables were edge glued. I attached a “border” around the tables (used kregg jig for attaching) and then glued particle board to the underside to help with warping. As pictured, both tables have the trestle style bottom. and the table top is attached to the leg in 6 locations with screws. As i’ve been looking through other forums, I’m well aware that its my own mistake that the table cracked. What i’m looking for is advice on how to attach a border around the table that still allows movement. and also best methods to attach the tabletop to the legs. Both tables are in the homes of the people who bought them. I got the dreaded phone call. Thanks for any help.


47 replies so far

View rwe2156's profile

rwe2156

3171 posts in 1682 days


#1 posted 01-27-2018 02:44 PM

A top has to be able to move so any time it is attached in a way that prevents, that, things happen.

In this case, the crack was caused by wood shrinkage but the would couldn’t move. Looks like its along the glue line. Also, the moulding attached to the end can be a problem. Better to route a profile in the end grain.

Reglue it & don’t use pocket screws. Use attachment blocks with oblong screw holes that allow for movement.

-- Everything is a prototype thats why its one of a kind!!

View Loren's profile

Loren

10477 posts in 3849 days


#2 posted 01-27-2018 03:25 PM

Anna White in particular has been noted for
publishing designs with troubling approaches
to wood movement.

There’s no issue with pocket screwing the border
on the long sides. The end grain you would need
to use some variant of a “breadboard end”. It
can be done by routing elongated slots on the
outside face of the border, installing screws and
filling the holes with elongated wood plugs.
Another way to do it it to route a long dovetail
in the back of the border piece. Sections of
mating dovetail are screwed to the exposed
end grain. The border piece would need to have
the dovetail profile filled at one end.

Still another approach which I am not recommending
for aesthetic reasons is to make new end caps
from end grain poplar. Since this wood will move
the same as the inside sections you can probably
get away with gluing or screwing it on from the
back. Taking it further, the table top can be mitered
at 45 degrees and an end cap with the same grain
orientation cut to fit the miter and form a “waterfall”
edge. This is however a technically tricky thing to
get right, depending on the tools you have on
hand. Some people claim to do it with a Festool
guide rail saw, but I have never tried.

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a1Jim

117328 posts in 3778 days


#3 posted 01-27-2018 04:09 PM

I agree with Loren about Annie white’s designs, she may have attractive designs but she knows nothing about wood movement and very little about joinery.Gluing the top to the apron is a guaranteed approach to a cracked tabletop, although wood can be allowed to move with pocket screws by enlarging the hole pocket screws go in, I don’t believe that’s not always the most fail-safe approach, the more traditional approaches have distinct advantages over pocket screws.(see link) another issue is the end boards goes across the grain of the table top also is trying to restrict the top from moving. (see 2nd link)
http://www.craftsmanspace.com/knowledge/17-ways-to-fasten-a-tabletop.html
http://www.finewoodworking.com/2003/10/01/understanding-wood-movement

-- https://www.artisticwoodstudio.com/videos wood crafting & woodworking classes

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a1Jim

117328 posts in 3778 days


#4 posted 01-27-2018 04:10 PM

BTW Welcome to Ljs

-- https://www.artisticwoodstudio.com/videos wood crafting & woodworking classes

View Carloz's profile

Carloz

1147 posts in 793 days


#5 posted 01-27-2018 05:05 PM

Your particle board base is the problem. Wood shrinks quite significantly when humidity drops. particle board does not.
Other reason of cracking mentioned in previous posts are of no importance here since the table top did not shrink because the wood was glued to the particle board.
You could go the route you chose but making your boards 1/16” or so thick. You’d save a lot of wood and prevent any problems with wood movement. Manufacturers go this way in maybe 95% of furniture these days.
I see no way of fixing it now besides taking off the top, making a chicken coop of it and making another top properly either by gluing veneer to it or changing the design to allow for wood movement.

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a1Jim

117328 posts in 3778 days


#6 posted 01-27-2018 05:15 PM

I agree with Carloz ,I missed the fact that you glued your tabletop to particle board.I don’t quite agree that the other inhibitors to wood movement are “of no importance” but the gluing of the top to the particle board is probably of the highest importance to start with, the removal of that, then the other issues still need to be taken care of too.

-- https://www.artisticwoodstudio.com/videos wood crafting & woodworking classes

View Lazyman's profile

Lazyman

2635 posts in 1588 days


#7 posted 01-27-2018 05:15 PM

Are you saying that you glued particle board to the underside of the top? if so, that sounds like the biggest mistake to me and what caused the joints between the tops individual boards to fail the way they did. Basically, my theory is that you locked each board in place and when the humidity dropped from what it was when it was built , the boards contracted laterally and pulled the joints apart because the PB backer would not let them move. Assuming that you cannot remove the glued on particle board, the only thing that I can think of that might allow you close the gaps would be to take a router or circular saw and cut grooves in the particle board lined up with each of the joints in the top. Not sure that you can actually repair the failed joints, because you usually cannot reglue PVA joints without removing the old glue, but it might help prevent them from getting any worse. If the end pieces are also glued on those will also restrict the lateral movement of the top and removing and reattaching with oversized pocket holes and no glue may help and make it easier to cut the grooves in the PB all the way to the end.

Of course, if I misunderstand…nevermind! ;-)

For future reference, battens using screws in oversized holes or slots would be a better way to help prevent or at least reduce warping while still allowing for wood movement.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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Woodknack

12431 posts in 2581 days


#8 posted 01-27-2018 05:28 PM

Step one is give the people their money back. There are many outstanding books on furniture making, read some and don’t sell anything until you have practiced and know what you are doing.

-- Rick M, http://thewoodknack.blogspot.com/

View jonross667's profile

jonross667

13 posts in 321 days


#9 posted 01-27-2018 06:22 PM

Thanks for all the advice. I’ll be going to look at the table Tuesday to see what can be done. I’ll post more pictures at that point.
I had a local lumber company do the glue-up for the table top, and they suggested that I attach some sort of furniture grade backer board, one that was a dry material. That’s why I went with the PB. But, I now realize that was my first big mistake.

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jonross667

13 posts in 321 days


#10 posted 01-27-2018 06:24 PM

Thank you, are you saying to attach a backer board with oblong screw holes? Or would that be for the border piece on the ends?


A top has to be able to move so any time it is attached in a way that prevents, that, things happen.

In this case, the crack was caused by wood shrinkage but the would couldn t move. Looks like its along the glue line. Also, the moulding attached to the end can be a problem. Better to route a profile in the end grain.

Reglue it & don t use pocket screws. Use attachment blocks with oblong screw holes that allow for movement.

- rwe2156


View jonross667's profile

jonross667

13 posts in 321 days


#11 posted 01-27-2018 06:27 PM

Thank you. I’ll check out those articles you posted.


I agree with Loren about Annie white s designs, she may have attractive designs but she knows nothing about wood movement and very little about joinery.Gluing the top to the apron is a guaranteed approach to a cracked tabletop, although wood can be allowed to move with pocket screws by enlarging the hole pocket screws go in, I don t believe that s not always the most fail-safe approach, the more traditional approaches have distinct advantages over pocket screws.(see link) another issue is the end boards goes across the grain of the table top also is trying to restrict the top from moving. (see 2nd link)
http://www.craftsmanspace.com/knowledge/17-ways-to-fasten-a-tabletop.html
http://www.finewoodworking.com/2003/10/01/understanding-wood-movement

- a1Jim


View jonross667's profile

jonross667

13 posts in 321 days


#12 posted 01-27-2018 06:33 PM

Yes, i glued particle board under the table top. As was recommended by the company who I had make the table top for me. I will try the cutting of joints in the particle board to see if that will help relieve the stress on the wood. Also, yes – the end border piece is glued on. Thanks!


Are you saying that you glued particle board to the underside of the top? if so, that sounds like the biggest mistake to me and what caused the joints between the tops individual boards to fail the way they did. Basically, my theory is that you locked each board in place and when the humidity dropped from what it was when it was built , the boards contracted laterally and pulled the joints apart because the PB backer would not let them move. Assuming that you cannot remove the glued on particle board, the only thing that I can think of that might allow you close the gaps would be to take a router or circular saw and cut grooves in the particle board lined up with each of the joints in the top. Not sure that you can actually repair the failed joints, because you usually cannot reglue PVA joints without removing the old glue, but it might help prevent them from getting any worse. If the end pieces are also glued on those will also restrict the lateral movement of the top and removing and reattaching with oversized pocket holes and no glue may help and make it easier to cut the grooves in the PB all the way to the end.

Of course, if I misunderstand…nevermind! ;-)

For future reference, battens using screws in oversized holes or slots would be a better way to help prevent or at least reduce warping while still allowing for wood movement.

- Lazyman


View a1Jim's profile

a1Jim

117328 posts in 3778 days


#13 posted 01-27-2018 08:02 PM

Hi again I teach adult woodworking and this term I’m actually teaching a class on table making.
I think you misunderstood you don’t need a baker board at all, you were given some bad advise where you got your wood, no one puts backer boards on hardwood tables.It’s the apron end boards(breadboard ends)that needs the connections that allow for wood movement.please do some research on wood movement and moisture content and breadboard ends before you make any more furniture for customers.
By the way, your tables look nice but it’s all about the details.

-- https://www.artisticwoodstudio.com/videos wood crafting & woodworking classes

View a1Jim's profile

a1Jim

117328 posts in 3778 days


#14 posted 01-27-2018 08:08 PM

When people talk about tables here are some the names of the different parts of a table.

-- https://www.artisticwoodstudio.com/videos wood crafting & woodworking classes

View jonross667's profile

jonross667

13 posts in 321 days


#15 posted 01-27-2018 09:23 PM

For my table, I didn’t have the traditional apron as mentioned above. I think understand how to join to the traditional apron with different types of fasteners. I have some of the metal Z type. What is the best method to attach a table top to pedestal legs? Would you use similar fasteners?


Hi again I teach adult woodworking and this term I m actually teaching a class on table making.
I think you misunderstood you don t need a baker board at all, you were given some bad advise where you got your wood, no one puts backer boards on hardwood tables.It s the apron end boards(breadboard ends)that needs the connections that allow for wood movement.please do some research on wood movement and moisture content and breadboard ends before you make any more furniture for customers.
By the way, your tables look nice but it s all about the details.

- a1Jim


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