table top separation question

[Gary Leatherland]

Last summer I built a dresser out of white oak. Just recently the 3 pieces I used on the top started to separate.
The gap between 2 of the pieces has opened up to about an 1/8 of an inch. On the underneath side of the top
I placed several clete which I both glue and screwed to the top to avoid this happening. Could a more experience
woodworker tell me where I went wrong? Is it the dry winter air that is causing this or is it something else? I'm
not sure what to do to correct this and I surely don't want to have the same thing happening to future projects.

Thanks in advance.:confused:

[Wade Lippman]

Your cleats might actually have caused the problem. The table top wanted to shrink, and would have except for the cleat. Since it couldn't shrink it broke apart. You have to attach it so allow movement. Many ways to do that, but glue is never allowed (except perhaps for a dab in the middle)

[Mike Schuch]

Your cleats might actually have caused the problem. The table top wanted to shrink, and would have except for the cleat. Since it couldn't shrink it broke apart. You have to attach it so allow movement. Many ways to do that, but glue is never allowed (except perhaps for a dab in the middle)

Yep, use elongated screw holes in the cleats to allow the top to move independently carcass. Gluing the cleats to both the top and carcass is what caused your separation problem.

[Judson Green]

http://woodbin.com/calcs/shrinkulator.htm

Thanks to Kent Bathurst for providing the link in another thread.

http://www.sawmillcreek.org/showthread.php?226526-Farmhouse-table-breadboards

Good reading, might help you in the future.

[Jim Dwight]

Just to add a consistent thought but with a little different phrasing. What you don't want to do is to join wood that is going in different directions. Your cleats had their long grain oriented across the grain of your top. Wood expands much more across the grain than along the grain. So your cleats resisted the movement your top wanted to do resulting in the separation. You can make a carcase of solid wood but you need all the pieces with their grain oriented the same. Then they expand and contract together.

Another thing you don't want to do is to join something like metal or plywood that doesn't move with moisture changes to wood which does in a way where the plywood or metal would resist the cross grain movement of the solid wood. That creates the same issue.

When non-moving pieces need to be joined to moving pieces, like your cleats to your top, you must allow the piece that is going to move to move. Slotted holes and screws are one way.

[Chris Padilla]

Adding to what Jim said, keep in mind that it depends on the wood species (some move a lot...some not much) and how wide that single board is. The wider the board, the more it is bound to move. How wide were each of the 3 boards you used? 6" each, maybe? Also, what about moisture content when worked--that should be in the 6-8% range. How about acclimation to your environment or shop conditions--did you pull the wood out of the unheated, non-insulated shed and take it into your basement and glue 'em up pretty quickly? Did any of the boards curl or warp or bow or twist or was it pure separation at the joints and things are flat other than that?

Had you not glued your cleats, you might've be okay as there was likely just a wee bit of room around the screws. As Jim above said, you would enlargen (or make slots) such holes to allow for some movement.

[Kent A Bathurst]

Your cleats might actually have caused the problem. The table top wanted to shrink, and would have except for the cleat. Since it couldn't shrink it broke apart. You have to attach it so allow movement. Many ways to do that, but glue is never allowed (except perhaps for a dab in the middle)

^^^This is exactly what happened. THe wood is gonna move, and there is nothing you can do to stop it, so you gotta go with the flow and design to allow for it.

[Mike Schuch]

A buddy of mine built a 15' gate in front of his RV pad several years ago. He didn't want it to sag so he over built it by welding the frame together out of some 2" square steel tubing. He then used some heavy duty self taping metal screws to mount the fence boards to the gate.

Several months later on a warm spring morning he heard what sounded like someone shooting off a .22 so he went out to investigate. Nothing, nobody was there. He went back inside and after a little while he heard the .22 going off again. He went out side and looked all around his property... nothing again. On the way back inside he was walking past his gate when "CRACK!" one of the 1/4" self taping screws holding the boards on let go and sheared in two. He calmly walked back inside and changed his underware.

[Bruce Wrenn]

For thousands of years we have separated stone blocks by drilling a series of holes, then placing dry wooden pegs in them, followed by dripping water on pegs. Expansion of pegs is enough to shear stone blocks in quarry. Wood is going to MOVE based upon the available moisture. You can't stop it, just allow for it.

[Andrew Hughes]

It's soo tru what everyone says,don't feel bad if your mistake was not enough room for expansion and contraction.Its the most common mistake wood worker make.Even I cut it close.
Mother nature gets to make the rules and if the project crosses the line it gets rejected!
I too knew someone that made a gate with big thick steel straps.To hold everthing from expanding.It didn't work Mother Nature won again.Gaps Gaps gaps. Wood is both mysterious and amazing ...Aj

[Gary Leatherland]

Thanks so much guys! You can't imagine how much I've been stressing over this. But this brings me to a couple of more questions. First, when I look at my store bought furniture, i.e. the dining room table, coffee table etc, there is no movement (that I can see) at all. Do they seal the wood somehow from absorbing moisture? And secondly, do I still glue my biscuits and edges together? And one more, would it be wise to make my tops out of several smaller pieces such as 4" rather than 8-9"?

It looks like Ive got several tops to take off and rebuild. Any way to save the tops?
Again I want to thank you all very much for your help! Building the furniture comes easy for me but it's the little tricks like you guys just gave me has been haunting me tremendously!

[Wade Lippman]

Bought furniture will allow for movement. Remembers screws aren't as fixed as you might think. You can seal as much as you want and it it won't help. There is controversy over whether you have to varnish unseen sides. Some say unequal water absorption causes warping; other say not. Me, I make an make an effort.

Some like several small pieces to avoid warping, but it won't do anything to avoid splitting. And sure, glue edges and biscuits. As long as the grain is all in the same direction the pieces won't move with respect to each other. Any elementary book on wood movement will discuss this.


BTW... Is you house airconditioned in the summer and humidified in the winter? You can get away with a lot of incorrect work now that you couldn't have 50 years ago because the humidity doesn't change all that much.
You can try working some glue in and clamping. I have had that work. It is probably a better bet to saw them apart along the split, rejoint and reglue.

[Gary Leatherland]

Thanks Wade. Well the house is not humidified in the winter but is air conditioned. And I think I am like you, I would try to varnish the unseen sides of any wood to, if for no other reason error on the side of caution.

Again, thanks for all your help. Much appreciated.

[Dan Hahr]

Just remove the cleats and let the wood sit for a bit. The gaps will probably close up in time. If they are too far gone, rip them with a thin blade along the glue lines and rejoin. You will only lose a small amount of width. Save an endgrain cutoff from your next top and screw it to a long grain board with one fixed screw at one end and two screws in slotted holes. Mark the end that is free to move. You will see it move back and forth as the humidity changes. It will help you know what the conditions are like when you are building your next piece of furniture.

Dan

[Kent A Bathurst]

First, when I look at my store bought furniture, i.e. the dining room table, coffee table etc, there is no movement (that I can see) at all. Do they seal the wood somehow from absorbing moisture?

Look closely - are the table tops solid wood, or are they veneered panels? They are good at it, so a quick glance won't always tell. THere is nothing inherently wrong with veneered panels - and one of their benefits is the substrate will not expand/contract with changes in seasons.




And secondly, do I still glue my biscuits and edges together? And one more, would it be wise to make my tops out of several smaller pieces such as 4" rather than 8-9"?

Yes - edge glue the boards to make up the table top. As long as the wood is properly dried, it should be stable. Use wide boards if you got'em - should be no problem.






It looks like Ive got several tops to take off and rebuild. Any way to save the tops?

Shouldn't be an issue with them. Pull the cleats, and go from there. If the top has separated, it may close back up on its own - but if you wait until high-humidity season, the reverse is going to happen, and it will close up. You might want to clamp it to pull it back together - that's what I would do, plus I'd let a little bit of thin CA glue "wick" into the crack just before I tightened the clamps.

IF there is a top built the same way that has not yet separated, get those cleats off immediately. THen - you're fine from there.

[Howard Acheson]

>>>> when I look at my store bought furniture, i.e. the dining room table, coffee table etc, there is no movement (that I can see) at all.

Almost all factory made furniture uses veneer over a composition material like plywood or MDF. These composition core materials do not expand and contract with changes in relative humidity but all solid wood materials will move.

[David Utterback]

I commiserate with you. I finished a chest of drawers 2 years ago and the top has breadboard ends. First, one edge glue joint failed and now the second one. In my case, the error was using older glue. Due to its construction, I will need to make a complete new top and recycle what I can on other pieces. By the way, I did glue the ends only in the center and allowed for movement in attaching the top to the case.

[Kent A Bathurst]

I commiserate with you. I finished a chest of drawers 2 years ago and the top has breadboard ends. First, one edge glue joint failed and now the second one. In my case, the error was using older glue. Due to its construction, I will need to make a complete new top and recycle what I can on other pieces. By the way, I did glue the ends only in the center and allowed for movement in attaching the top to the case.


Whoooaaaaaaa, cowboy.

How about this?

Run the to thru the TS, or the Green Track Saw, with the saw kerf right down the line separating the breadboard end from the top.

Use the method of your choice to put mortises in both sides of each line, and put in loose tenons.

Glue the tenons into the table top; make the outer ones too narrow to allow for expansion; re-make the expansion slots on the outer M&T joints however you did them the first time.

Seems a bit extreme to toss both the baby and the bathwater.

[mike mcilroy]

Seems a bit extreme to toss both the baby and the bathwater.

Maybe the fun of making a new baby? :D