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Wood Slab Counter Tops, Joining together

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Forum topic by bmerrill posted 01-02-2020 09:59 PM 474 views 0 times favorited 5 replies Add to Favorites Watch
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bmerrill

103 posts in 840 days


01-02-2020 09:59 PM

Topic tags/keywords: maple joining counter top

Present project is a counter top for the garage/workshop.
The top is constructed of 1.5” red maple slabs (2) glued together to make a width of 30”.
One section is 12’-3” long the other is 13’-6”.
The sections will be joined together to make an “L”
The rear edge will be supported continuously along the wall on 2” angle iron.
The joint will be a butt joint where the end grain of one section is against the long grain of the other.
Concern is expansion of the width of each top since the joint will be similar to a breadboard on a table.

How would you make this joint to minimize the effects of expansion?

-- You are not told the truth, you have to learn the truth.


5 replies so far

View CaptainKlutz's profile

CaptainKlutz

3139 posts in 2261 days


#1 posted 01-02-2020 10:50 PM

Look for miter bolts in the kitchen countertop area of any BORG.
Rockler sells a fancier version called tite joint fastener.
Zip-tite sells extra fancy/expensive version that has quick release.
Easy to find once you know where to look, or what they are called. :-)

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

View AlaskaGuy's profile

AlaskaGuy

5788 posts in 3076 days


#2 posted 01-02-2020 11:24 PM

https://www.youtube.com/watch?v=qXee2-Pkg_k

-- Alaskan's for Global warming!

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bmerrill

103 posts in 840 days


#3 posted 01-03-2020 01:01 AM

Have the zip-tie bolts and will be installing them to pull the joint together.
Concern is the difference in expansion between the end gain vs the straight grain of the slabs at the side to edge joint. This is a very similar to a farmhouse table with breadboard ends.

-- You are not told the truth, you have to learn the truth.

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CaptainKlutz

3139 posts in 2261 days


#4 posted 01-03-2020 10:10 AM

1) How much is going to move?
Gluing together boards ‘butcher block style’, essentially makes the panel quarter sawn. QS lumber direction has 2nd lowest amount of movement of the 3 types; Radial, Tangential (highest), & Length (negligible). With QS lumber, the highest (tangential) movement dimension is now vertical with 1.5” top thickness. The published average of the radial value is approximately half the tangential.
Try the Shrinkulator for exact numbers.

2) The miter or zip bolts are designed to allow for movement. One design concern is going to the distance between the bolts, on the end grain panel. This is going to change the most of all your dimensions in the JOINT. But the bolts are installed in oversized holes, and easily absorb the typical movement from a couple percent humidity change.

IMHO – Bigger concern with any ‘L’ shaped table design is how the table top is attached to base, and total movement of pieces relative to each other. Need to make sure the top can float slightly, or you risk trying to push the entire ‘L’ side of counter out of place, or cracking something. The simplest way to avoid issue is elongated holes on the mounting brackets for the panel with end grain portion of the joint. Need to allow enough movement for the (radial movement) width of the other panel. For a 4% change in RH, you will see 0.25” of radial movement in 30” red maple top. So I would slot the mounting holes for one side more than 0.25” long. My numbers could be wrong as I did this quickly, so check it yourself.

Hopefully it all makes sense: you need to allow one side of the ‘L’ to move relative to the other side to reduce stress on joint.

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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bmerrill

103 posts in 840 days


#5 posted 01-03-2020 01:58 PM

Captain Klutz,

Thank you for the reply.

I totally understand what you’re saying. Using the Shinkulator is the reason for my concerns and questions; looking for a second opinion to make sure I’m not missing something.

My plan:

The counter top will be supported by the angle iron along the back sides. Slots for the bolts will be cut in the angle iron to allow for movement in the cross-grain direction. Threaded inserts will be installed to accept the bolts. A 3/8” gap will be left between the wall and the top to allow for expansion. Gap will be covered with a trim board.

The front edge will be supported by several legs made of 3” x 2” I-beam leaving the bottom open for rolling tool storage. The top will not be attached to any base cabinets.

At each leg location will be a steel plate support running from the back to the front (cross grain) and bolted to underside of the top. The bolt holes will be slotted to allow for movement.

The joint between the tops will be made using a butt joint and held together by Zip-tite bolts (3).
The underside of the joint will be a leg and a metal cross support.

-- You are not told the truth, you have to learn the truth.

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