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 Post subject: Keeping a table top flat
PostPosted: Tue Jun 26, 2018 7:03 pm 
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Location: Rolling Meadows, IL. USA
Keeping a table top flat
I am making a trestle table out of southern yellow pine 2x construction lumber, the top will be a (glue up) about 7' long and 3' wide.
How do I keep the top from warping if I just glue and screw boards to the glued up top I hear it will probably crack.
I've not had a problem on hard wood yet gluing and screwing the supports to the top well dried and finished on all sides.
Cracking or splitting would be very bad as this will be sold with the possibility of selling more with benches and chairs plus a long drive to get the lumber no one seams to sell it around here.

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PostPosted: Tue Jun 26, 2018 9:04 pm 
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Hey Monte,

Make sure that at the holes for the fasteners that connect the top to the trestles are slotted. That is, the holes in the trestles should be slotted. This will allow the top to expand and contract as humidity dictates. If you are breadboarding the ends, you need to slot the holes in the ends of the table top tenons as well.

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Tom

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PostPosted: Wed Jun 27, 2018 11:32 am 
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DADDY GLOVES: An outside the box :idea: When you select the 2X material for the project, pick the widest boards you can find. The boards generally come from closer to the center of the mill log. Then, if you rip the project stock off the outside edges you will wind up with quarter sawn or rift sawn stock to glue up. The pith material left from the ripping can be used in less visible project parts. If you use splines or biscuits to align one surface you will seriously degrade the dimensional change. As TMS points out, elongated attachment holes in the battens under the top will allow for whatever movement there is. The point about breadboard ends is well made also. One down side of ripping the stock is that you give up any cathedral plain sawn grain look the boards have as planks. Just another cat skin in the hopper with hopes it will be thought about :wink:

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PostPosted: Fri Jun 29, 2018 9:40 am 
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If you have enough thickness to the trestle or batten, you can simply counterbore its top surface with a 1" bit. When you screw the table top on from below, this provides a gap for a fairly long screw to tilt or bend a bit, allowing some expansion and contraction of the top. As Newtooth points out, using quartersawn stock will help by cutting down the expansion and contraction by about half.


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