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Hello all,
2 months ago, I put together a red oak table that had very basic elements. I'm learning the craft and, in a previous attempt, built a poplar table with the same specs. When I brought the table to my apartment (I built it at my home in the country), the steam heat of the apartment shrank the wood and it split in several places. This time, I followed an expert's advice and created a new top out of the oak. I let the wood sit in the dryer upstairs and had it sit in a sunny dry room for a month. As per advice, I put 5/16 grooves along the bottom to ease any shrinkage. I screwed down large wooden crosspieces on the underside and finished the table off with 3 inch breadboards. It is stained, limed with wax and varnished with 4 coats of a tung oil and urethane mix. It was fine for 2 months in the apartment but, as the winter took hold and the steam heat came on full-time, a similar problem has occurred. It is slowly splitting from dry shrinkage. This time, I want to save it. There is very little outer-edge shrinkage so it is splitting from within. What can be done in this case? Are there several suggestions other than cutting off the breadboard and clamping and gluing it back? It's too nice and too expensive to let go. Please help. Below are attachments
Thanks for any.
Al
 

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The breadboard should not be glued. It should be pegged in the center, and at the ends, with the end holes in the top's mortise elongated to allow movement.
 

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In my opinion the boards on the bottom are the biggest part of the problem. Those are the "fixed points" that are causing the cracking.

Wood expands and contracts across the width, with very little if any change along the length. Since the boards on the bottom are running the opposite way and there will be little if any change in the length, they created "fixed," unchangeable surfaces the top is screwed to. So the top is changing with no allowance for the change.

You'd have to use elongated slots for the screws on those cross pieces so the top could move vs. the cross pieces. Or just take them off completely.

The leg structure is another possible "fixed point" that could contribute to the cracks. Are there aprons between the legs going both directions? If so, there are a type of clip sold at woodwork supply places that fit into a slot cut into the aprons that allow for movement in the table top.
 

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Sorry to hear about your problems

but even sorrier for some of the advice you have been given. First off, those battens on the underside need to come off. No two ways about it. Secondly, you need to run a humidifier in your house during the heating season if you plan to happily cohabitate with wooden furniture. You'll feel better, your wood will be happier and your heating costs will go down because the moisture you put into the air will hold the heat longer. As to the breadboard edges, if they are attached solidly along their length (like I,m guessing that they are), they will need to be removed and attached properly. Typically, they are to be fastened in the center and then provisions are made that allow the ends to come and go with changes in the moisture content of the wood. The normal procedure would be a dowel through with a side to side slot in the tongue of the table top. Don't forget to relieve the length of the tongue on both ends to allow room to grow in the groove in the breadboard end (assuming that the groove does not go all the way from end to end). As to fastening the top to the skirt boards (if there are any) you can use pocket screws into the long sides providing that you don't install any closer than 18 to 20 inches from their ends. This will allow the top to move by springing the apron with no ill effects to the structure.

I provide a 100% money back guarantee on any advice I have offered here that fails to perform up to your expectations. Upon reciept of complaint, all funds collected will be returned in like manner as they were recieved.

Best of luck
Ed
 

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Discussion Starter #5
All news to me.

Thanks for all the responses. I got weak advice about the breadboards. As suspected they are glued and biscuited. I will cut them off and reattached as per your suggestions. The table top was never attached to the apron due to my fear that this might happen from that procedure until the winter passed. So it has to be the combo of crosspieces and breadboard applications. (I've had a humidifier going all the time). eek. I don't look forward to this. Now I know.

Al
 

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Thanks for all the responses. I got weak advice about the breadboards. As suspected they are glued and biscuited. I will cut them off and reattached as per your suggestions. The table top was never attached to the apron due to my fear that this might happen from that procedure until the winter passed. So it has to be the combo of crosspieces and breadboard applications. (I've had a humidifier going all the time). eek. I don't look forward to this. Now I know.

Al

Don't forget to fix the crack. Large table tops in questionable locations become failsafe when the "field" of the table is a hardwood plywood of choice, and is edge banded in solid hardwood.






 

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I'm learning the ropes on wood working. Is there any good resources to read up on how to prevent cracks from happening?
Not that I can thing of. There aretons of things that can lead to cracks, buit the two biggest ones are moister and not being able to move. So, if you take of these two problems you should be in good shape.
 

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As long as those breadboards on the ends of the table aren't glued, and as long as the screw holes are oversize on the pieces on the bottom, to allow for seasonal movement, you should be OK.

There are also other ways of attaching the top to the table. Attached is a pic showing one way of attaching a top to a trestle table (the one at which I'm typing now)! :thumbsup:
 

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I'm learning the ropes on wood working. Is there any good resources to read up on how to prevent cracks from happening?
What you need to pay attention to are places where the grain crosses, like where you fasten a tabletop to the frame and legs underneath.

Just remember that the wood swells and shrinks ACROSS the grain as moisture is taken up in summer and given off in winter, but it doesn't really expand/contract (for practical purposes) along the grain.

What that means is that if you securely fasten two pieces of wood with their grain at 90° angles, you could have problems with seasonal expansion/contraction, depending on how wide the board(s) is.

With narrow stuff, you can often get away with it because we're not talking about THAT much movement. But with something wide like a tabletop, which might expand and contract across the grain by 1/4" in the course of a year, it's a PROBLEM.

One way of dealing with it is to not use glue on joints across the grain, and to drill the holes for screws oversize by 3/16" if that makes any sense...

Good luck.
 

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MC of the lumber?
Bread board must allow the top to move.
Bottom battens must allow the wood to move.
The design is trying to not let the wood move so the wood moved and cracked at its weakest point.

The slits on the bottom do nothing to stop wood movement across the grain. In fact they me be an area where wood would crack due to reduced thickness making that a weak area.

When your top reaches an equilibrium moisture content with the environment that it is in, it will stop the shrinkage. It will still do seasonal movement but the overall shrink will cease.
Then you could fill/refinish, but the crack may still be noticeable and even crack the fill (but not real bad)

Ironicly, if you would have left off the bread board, slits, bottom battens, the top may not have cracked (unless it was real wet wood to begin with)
jim
 

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Discussion Starter #13
Update

Again, thanks all. I'm glad I posted this problem. I can extract from your responses about what NOT to do next as well as what I can try to save the table. The battens on the bottom are off and the crack seems to have relaxed under the same conditions, a dry, steam- heated apartment. I have waited to see how far the wood would pull further before I sliced and diced it. The last comment by solidwoods finished off all my concerns. To know that not only is there a limit to shrinkage but that the crack can be glued and filled(without having to split it further and joining it back)thus diverting a bigger headache. I have removed one breadboard so far (the one nearest the split) and am watching the other side to see what it will do next. It hasn't made a move yet(although that shoe may drop). Luckily, in the beginning, I let the planks dry for a month and mostly in a sunny, dry room. It obviously was my naive construction that created the mishap. My next table should go smoother.
:blink:
 

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Shrinkage

Love this thread - well informed. Shrinkage in wood does occur noticeably lengthwise and may well depend on the species. It obviously doesn't shrink at anywhere near the rate in width. It may not be noticeable since it is often compared to other woods fastened in the perpendicular orientation. I have two pieces of ash (railings) that have shrunk lengthwise by 5/8 of an inch or 16mm over a length of 20 feet or 6 meters. Not significant maybe but still noticeable.

Also I find that the best way to dry wood is to dry it in an identical environment for both humidity and temperature and the variability ie sun shine where it is to be used. Ideally it should be dried in the same room.

I try to keep the relative humidity in my house between 40% and 65%. Above 65% I get condensation and noticeable electronic failures, corrosion and mould. Below 40% I get issues with cracking glue in furniture joints. For the piano according to the tuner 42% is ideal.
 

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Most of the wooden oak dining tables and chairs come in a lightly oiled oak finishthat will complement any dining room or kitchen. You should fix the crack. This is such a nice post. Thanks for discuss this.
 

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Shrinkage in wood does occur noticeably lengthwise and may well depend on the species. It obviously doesn't shrink at anywhere near the rate in width. It may not be noticeable since it is often compared to other woods fastened in the perpendicular orientation. I have two pieces of ash (railings) that have shrunk lengthwise by 5/8 of an inch or 16mm over a length of 20 feet or 6 meters. Not significant maybe but still noticeable.


As I read this, it sounds like you have got the direction of shrinkage (which is movement to include expansion), reversed. Wood moves (expansion/contraction) across the grain (width...so to speak). Expansion/contraction lengthwise is negligible.








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As I read this, it sounds like you have got the direction of shrinkage (which is movement to include expansion), reversed.
Indeed, it's a bad use of words trying to be brief. Intended was to say "It obviously doesn't shrink at anywhere near the rate that it shrinks in width." Using these measurements the lengthwise shrinkage after installation was a change of 0.27%. I measured widthwise shrinkage after installation at six points and the results ranged between 1.7% and 2.6% with an average of 2.25%. So I measured a ratio of lengthwise shrinkage to widthwise shrinkage of about 1 to 8. The wood was not dried before installation.
 
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