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Is laminating two hardwoods face-to-face (not edge grain) going to cause issues with differing rates of expansion across the grain? I plan on laminating 1" of maple to 1" of padauk, should I just use plywood to build up the depth instead of the maple?

In another thread I was enlightened as to how to properly attach bread boards ends (thank you). But I do have a few more questions regarding the result of that type of glue up:

1) Is that joint going to be tight seeing as only the middle 1/4-1/3 is glued?

2) Seeing as the purpose of this looser joint is to allow for cross-grain expansion, is there worry of any hard finish that crosses that joint cracking later on if the wood does expand that much? When people talk about an 1/8th+ of movement it seems likely.



Sorry about all the questions regarding this project over the last 2 weeks. It's my first solid wood project of this scale so I am just learning the ins-and-outs of dealing with expansion issues!



(thanks in advance, Cabinetman:laughing: )
 

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Is laminating two hardwoods face-to-face (not edge grain) going to cause issues with differing rates of expansion across the grain? I plan on laminating 1" of maple to 1" of padauk, should I just use plywood to build up the depth instead of the maple?
Gluing anything for a buildup can be a cause of limiting movement issues for cross grain.

In another thread I was enlightened as to how to properly attach bread boards ends (thank you). But I do have a few more questions regarding the result of that type of glue up:

1) Is that joint going to be tight seeing as only the middle 1/4-1/3 is glued?
The middle can be fastened, and along the way to the edges, elongated slots provide the "slip" in case of E&C. The fit of the method of how the BB is attached to the ends should be a close friction fit, and the screws with washers (or washer head screws) can be snug but not tight.

2) Seeing as the purpose of this looser joint is to allow for cross-grain expansion, is there worry of any hard finish that crosses that joint cracking later on if the wood does expand that much? When people talk about an 1/8th+ of movement it seems likely.
That's a good question. If the wood was acclimated and finished properly, its likely that it won't happen, but there is always the possibility that it could.





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As I mentioned in my first reply, I would use lag bolts instead of dowels to pull the joint tight, then plug the holes. Drill out the bread board part of the lag bolt hole about 1/16" bigger to allow for movement and use a washer under the bold head. Actually, I would even elongate the bolt holes at the ends of the bread boards to about 1/8" bigger than the bolt, by reaming the bottom of the hole, which will be in the dado slot. This will keep the joint tight and still allow movement.

To be safe on the finish, I would put a tiny bevel on the joining edges of the bread board and main panel. This will create a natural separating line. Just hitting the edges with sandpaper at a 45 degree angle will make a parting line.
 

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>>>> Seeing as the purpose of this looser joint is to allow for cross-grain expansion, is there worry of any hard finish that crosses that joint cracking later on if the wood does expand that much?

Yes, if there is any movement along the seam, the finish will be "cracked". That's just the way it is. In some cases the movement is not enough that is exceeds the elasticity of the finishing material. Oil based varnishes and poly varnish are more flexible than waterborne poly, lacquer and shellac. If those finishes are used. There will be a cracking of the finish over the seam. It's one of the reasons I try to talk folks out of using them.
 

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Discussion Starter #5
Thanks Cab-man, as always. ;)

MNsawyer, the same thought about a small bevel occurred to me as well. At least that way if there is cracking it gives a natural fault point.

Howard, thanks for that feedback. I was leaning toward oil finish since the start, I think that helps me make up my mind though. I was originally thinking about it just because I didn't want to introduce any H20 to the piece.



Kind of a follow-up question about my padauk, if you guys don't mind...I just cut in to it today and the edge is bright orange (I expect a color difference). Lots of people have told me it starts "red and turns an ugly brown" but if that bright orange is the "desired red" color and the "ugly brown" is what the board came looking like, then I love the "ugly brown." It's more a very deep red to my eyes.

http://imgur.com/Tyix9gJ
 

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Making sawdust in MS
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When using dowels for the breadboard ends, you want to do a draw bore type joint. In other words , drill a hole in your breadboard where you want your dowel. Slide the breadboard over the end of the table and mark the spot with a pencil. Take your breadboard off and drill the hole just a tad closer to the shoulder of the tenon than where it is marked. This way, when you do insert the dowel it will pull the breadboard end tight, and the elongation of those outer holes allow for the seasonal movement that will come.
 

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Discussion Starter #7
When using dowels for the breadboard ends, you want to do a draw bore type joint. In other words , drill a hole in your breadboard where you want your dowel. Slide the breadboard over the end of the table and mark the spot with a pencil. Take your breadboard off and drill the hole just a tad closer to the shoulder of the tenon than where it is marked. This way, when you do insert the dowel it will pull the breadboard end tight, and the elongation of those outer holes allow for the seasonal movement that will come.
Ahhhh I think I get it now.

So it would like: / \ But then when it expands laterally the dowels look more like | |. Grants that is an exaggeration of the center dowels, or do you do that to all the dowels?
 

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Actually you'd elongate them like __ __. The center hole would be left the size of the dowel, and the outer holes will be elongated. IOW, ____ . ___
Only glue the center few inches, glue the center dowel in completely. The outer dowels get glued on just the last part that passes through the BBend. I hope I haven't confused you.
 

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Here is a pic of how I did my drawbore.



image-423041601.jpg


The bottom is where I marked the hole and the top is where I drilled it.


image-790568964.jpg


This shows how I elongate the outermost holes.



image-2781917758.jpg


This is my center hole.
 

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These pics were shot of the bottom of the table, because you don't dowel it all the way through, just on the bottom. Unless of course that is the look you're going for.
 

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Discussion Starter #11
These pics were shot of the bottom of the table, because you don't dowel it all the way through, just on the bottom. Unless of course that is the look you're going for.
Okay I follow you now! Had to think it over a bit.:laughing: Thanks!
 
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