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Large table. concerns for expansion and contraction

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Forum topic by needshave posted 03-14-2017 01:21 AM 2585 views 1 time favorited 39 replies Add to Favorites Watch
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needshave

168 posts in 1797 days


03-14-2017 01:21 AM

Topic tags/keywords: farm table oak expansion and contraction mortise and tendon dowel question resource tip

I have many years of woodworking experience under my belt, but primarily in the replication of historic moulding and features of historic properties that we restore. I have built a few large ornate bars but the width of the bar typically does not exceed 24” and without bread boards.

Now I want to build a large Oak farm table, with width approaching 48” and breadboards. I’m concerned about the expansion and contraction both the table top and the bread board will see. I will most likely make the top of 8/4 rift cut Oak, with a 10” bread board. the table will be 96” long. The boards making up the top will probably be either dowed or more likely put together with loose tenons. The bread board will most likely be the same, but thats where the concerns lie, I know the opposing or opposite direction of the grain will expand and contract differently than the table top. And suggestions from experience you might be able to share? I appreciate your thoughts.


39 replies so far

View jerryminer's profile

jerryminer

805 posts in 1279 days


#1 posted 03-14-2017 02:15 AM

No need for dowels or tenons in the long-grain glue-up, unless you want them for alignment. Modern glues will adhere well-made long-grain joints better than the internal adhesion of the wood itself.

Traditional breadboard ends allow for expansion with slotted holes and no glue, except for the very center:

-- Jerry, making sawdust professionally since 1976

View Rick_M's profile

Rick_M

10630 posts in 2217 days


#2 posted 03-14-2017 03:43 AM

48” is very wide for a table, makes conversation and passing more difficult.

-- http://thewoodknack.blogspot.com/

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needshave

168 posts in 1797 days


#3 posted 03-14-2017 03:52 AM

Thanks Jerryminer for addressing the question. Your comment does help!

View WhyMe's profile

WhyMe

910 posts in 1398 days


#4 posted 03-14-2017 01:53 PM

Just glue up of the top panel by flat butting the edges. Joint the edges square and flat for a good bond. A 10” bread board end is quite wide, but don’t solid glue it to the end of the panel. The panel needs to float inside the bread board end so not to split. Only use glue on the center few inches to the panel and peg the ends as shown in jerryminer’s post. Leave plenty of room in bread board ends for movement of the top.

Here’s a farm table I made using bread board ends. http://lumberjocks.com/projects/300306

View rwe2156's profile

rwe2156

2714 posts in 1318 days


#5 posted 03-14-2017 02:31 PM

Are you referring to the breadboard moving? Keep the bread board pins closer to the seam be sure the tenons extend at least 1/2 way into the bb.

That is an extremely wide bb. You will need 5” deep tenons or if the apron is supporting at least to within 3” of the edge you could get by with 3” tenons. If this is a trestle table or the bb is unsupported, I wouldn’t make it more than 5” wide.

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

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needshave

168 posts in 1797 days


#6 posted 03-15-2017 01:05 AM

Why Me…: thanks so much for your comment and link. It was a big help. This table needs to be oak as well and your table turned out beautifully. The details on your bread board help a great deal. In regard to the table top glue up, I was somewhat concerned about table top cupping, I was going to mortise and tenon the joints to provide additional protection from cupping and strength. You don’t feel necessary.

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needshave

168 posts in 1797 days


#7 posted 03-15-2017 01:23 AM

rwe2156….. Yes. I’m concerned about the moving of the breadboard. So let me see if I understand fully what you’re saying. Let say the tenons are 5” long, you’re saying rather than pin at 2.5” from the seam, locate the pins closer to the seam say 1.5” ? Is that correct? Yes the BB is quite wide. The table is a duplicate of an existing table left in a building that I purchased. The building dates 1896 and the table appears to be close to that vintage. The bread board is supported by 4 out riggers that are supported and mounted to the apron. They support the BB, but are not attached to it.

Thanks again for your comments.

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WhyMe

910 posts in 1398 days


#8 posted 03-15-2017 01:29 AM

To reduce cupping of the top flip the boards so the end grain alternates.

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needshave

168 posts in 1797 days


#9 posted 03-15-2017 02:12 AM

Yes, Agreed. I certainly plan to do that. What are you using for glue? Is there an Accepted standard most use her on LJ? I have been using Franklin Titebond !!.

View Tony_S's profile

Tony_S

766 posts in 2920 days


#10 posted 03-15-2017 09:09 AM


Are you referring to the breadboard moving? Keep the bread board pins closer to the seam be sure the tenons extend at least 1/2 way into the bb.

That is an extremely wide bb. You will need 5” deep tenons or if the apron is supporting at least to within 3” of the edge you could get by with 3” tenons. If this is a trestle table or the bb is unsupported, I wouldn t make it more than 5” wide.
- rwe2156


This…100%
I’d also suggest drawboring the pins.
eg. http://www.thewoodwhisperer.com/videos/drawbored-mortise-tenon/

To reduce cupping of the top flip the boards so the end grain alternates.
- WhyMe

Again…100%

Yes, Agreed. I certainly plan to do that. What are you using for glue? Is there an Accepted standard most use her on LJ? I have been using Franklin Titebond !!.
- needshave

The standard here (if there is one) would be Titebond 3, although most wouldn’t be able to tell you why the use it, other than it works?
There’s no real advantage to TB3 on an interior project other than a longer open time. On the other hand, depending on your experience level, and efficiency during a large scale glue up, a longer open time might be an advantage for you.
Other than that, any yellow PVA will do. The only obvious difference between brand names is open, and set times. Most of which are similar.

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

View Rick_M's profile

Rick_M

10630 posts in 2217 days


#11 posted 03-15-2017 05:53 PM



To reduce cupping of the top flip the boards so the end grain alternates.

- WhyMe


This is a myth, there is no truth in it, and it’s been debunked many times for decades. Honestly I have no idea who started that myth or why it keeps getting repeated.

-- http://thewoodknack.blogspot.com/

View DirtyMike's profile

DirtyMike

637 posts in 739 days


#12 posted 03-15-2017 06:23 PM


To reduce cupping of the top flip the boards so the end grain alternates.

- WhyMe

This is a myth, there is no truth in it, and it s been debunked many times for decades. Honestly I have no idea who started that myth or why it keeps getting repeated.

- Rick M

Can you elaborate more on this rick?

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Rick_M

10630 posts in 2217 days


#13 posted 03-15-2017 07:12 PM



Can you elaborate more on this rick?
- DirtyMike

I was coming back to re-write my post and make it less – confrontational, but too late, oh well.

First, alternating boards isn’t going to prevent any one board from cupping. A flat sawn board will naturally want to cup toward the bark side, or as they say “flatten the smile”. But if the board is subjected to rapid moisture loss or gain on one side, the wood will expand or shrink on that side and cup accordingly regardless of ‘bark side’. Second, the claim is usually that alternating the grain will create a washboard top instead of the entire top cupping the same direction. But that’s only true if all boards cup. And IF that did happen, it would still be undesirable because fixing a washboard top means planing down the top and bottom and refinishing. Whereas if the top cups all in the same direction, fixing is relatively easy by kerfing the bottom, refinishing, and reattaching the top (which I have done). I’ve arranged the grain for best appearance and ease of planing on my tables and it had no influence on cupping.

Once I went back through all my woodworking texts to see if I could find an origin for this idea of alternating grain and it wasn’t in any of them so I don’t know where it got started. Regardless, even if it were, I find no truth in it and even if it were true, the result is undesirable.

-- http://thewoodknack.blogspot.com/

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DirtyMike

637 posts in 739 days


#14 posted 03-15-2017 07:16 PM

nailed it, thanks rick

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WhyMe

910 posts in 1398 days


#15 posted 03-15-2017 07:27 PM

Cupping was the wrong term and I was not referring to doing the flip to control it in one board. I was suggesting flipping the boards to minimize bowing of the overall top. I’ve made plenty of tops and I do find an advantage of alternating the grain to help with controlling overall bowing.

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