butt joint for L shaped walnut slab bartop - Woodworking Talk - Woodworkers Forum
 
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post #1 of 10 Old 12-02-2011, 12:15 AM Thread Starter
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butt joint for L shaped walnut slab bartop

I'm looking for advice on how best to join two pieces of Claro walnut slab 10/4 thick for a bar top. It's an "L" shaped bartop with the long piece measuring 20.5"x91" and the shorter piece 20.5"x32". I'm going to do a butt joint and I'm trying to figure out the best way to join them with minimal movement.

I'm thinking about mirror cutting the top edge about 3/4" deep with a router and leaving the meat of the end cut (small side) long to fit into a rabbet on the long piece. I was thinking I could have the top joint tight for on the surface and leave a little room in the rabbet below, but now I'm realizing that you'll see that profile at the end of the bar.

Both pieces are from the same slab and are currently around 8-11% on the moisture meter.

Any suggestions would be appreciated!
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post #2 of 10 Old 12-02-2011, 02:30 AM
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There are some special fasteners for this that are used to join countertops at corners. Sort of a bolt that fits into a routed recess then as it is tightened it pulls the joint together. I bet CMan knows the name and will post it or provide an even better solution
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post #3 of 10 Old 12-02-2011, 09:59 AM
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There is nothing you can do to "minimize" wood movement except get the moisture content as close to the average ambient moisture content of its environment prior to fabrication.

The best you can do otherwise is to control where the effects of the movement affect things the least.

I would cut tightly fitting splines of 1/2" appleply or the good baltic birch, and insert into dados without glue, and use "dog bones" from the bottom as the previous poster said.

I would glue 3" of the joint on the side facing the barstools so all the movement occurs on the other side of the bar.

Experience is something you get only just right after you needed it.
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Last edited by clampman; 12-02-2011 at 10:06 AM.
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post #4 of 10 Old 12-02-2011, 10:12 AM
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I wouldn't use glue. You can use what's called "tite joint fasteners". There are two basic types, properly installed both work very well.








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post #5 of 10 Old 12-02-2011, 11:24 AM
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See I knew you would know what they were called
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post #6 of 10 Old 12-02-2011, 12:45 PM
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Quote:
Originally Posted by DST View Post
See I knew you would know what they were called
Sometimes I get lucky.








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post #7 of 10 Old 12-02-2011, 12:47 PM
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Quote:
I wouldn't use glue.
I wouldn't either except for the 3" of joint as I indicated to force wood movement to the end of the joint where it cannot be seen.

"Dog bones" are countertop connectors which have been in continuous use since I first got started in this business in the 60's and which are carried by every industrial/commercial supplier of countertop fabrication materials I've ever been to.

It is nothing more than a galvanized bolt going through 2 galvanized bars, one drilled in the center, the other tapped in the center to accept the bolt threads. You rout the dog bone shape into the bottom of the countertop across the joint and bolt it together.

Experience is something you get only just right after you needed it.
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post #8 of 10 Old 12-13-2011, 04:31 PM
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The counter top connectors are used in homogeneous material like particle board,mdf or granite. If the joint is mitered, then the joint will open up with seasonal changes (if it lives in a part of the world with seasonal moisture changes).
Check out a picture frame made of wide solid wood. The inside corner will open if gets dryer and the outside will open if it gets more humid. This is one of the reasons veneer was used once wide mitered wood structures are designed
If the bar corner was a large butt joint, the movement of the joint needs to be allowed for similar to the use of a breadboard end on a table.
Pardon me if I am misunderstanding your project ?
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post #9 of 10 Old 12-16-2011, 10:29 AM Thread Starter
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Thanks!

Thanks for your replies guys! I ended up doing a shiplap joint with two dog bones. I have a nice tight joint on the top of the bar surface with a tiny bit of room on the bottom. Seems to work out well so far. Hopefully it holds up.

Thanks again for taking the time to reply.
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post #10 of 10 Old 12-25-2011, 01:48 AM
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Quote:
If the joint is mitered, then the joint will open up with seasonal changes (if it lives in a part of the world with seasonal moisture changes).
Check out a picture frame made of wide solid wood. The inside corner will open if gets dryer and the outside will open if it gets more humid.
Bob,

There is a difference between a picture frame and an L-shaped bar top. The only way two mitered pieces of wood will open as you have indicated is if the ends of each piece are solidly held in place.

Let's say that whereever the original poster installed his bar top his maximum seasonal moisture content change would result in 5/16ths total width change in a piece of 20 1/2" wide walnut. So the total amount of change between the two would be 5/8".

Lets say teh OP installs the top at its maximum moisture content (highly likely).

So if the OP did not rigidly fasten the short leg of the bar top, and dog boned the miter, the miter would not crack at all, it would simply change it's angle. At its maximum shrinkage value we started with, that angle would be 88.226 degrees instead of the 90 degrees he started with.

With the additional length of the short leg added to the total miter shrinkage, that short leg would move .9911 inches total at the end of it, assuming the long leg was rigidly fastened. One inch. If he could deal with that, then it could be mitered without cracking and with the entire joint glued.

I did just that on a solid cherry L shaped desk in 1982 in Colorado, and it was fine even after being moved to Houlton Maine in the early 2000's. I used 4 or 5 dog bones and glued the joint. The base just moves back and forth with the movement of the top.

The OP went with the butt joint and cannot glue any but three inches anywhere he wants to in the joint or risk either splitting the top or breaking the glue joint. If he glues on either end of the joint he will get 5/16th shrinkage on the other end of the end grained board. If he glued in the middle, he'll get 5/32nds on each end of it. If he used no glue, he will get it in the direction of the dog bone with the least torque. Hopefully he made the channels wide enough for the connectors to rack as the butt end board moves.

I'd have splined the joint myself, to insure that both boards remain on the same plane, and see no advantage to a half-lap joint in this application. Hopefully, the OP will give us an update in a year.

Experience is something you get only just right after you needed it.
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Last edited by clampman; 12-25-2011 at 01:55 AM.
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