Wood movement affects bench legs

[petertay15]

I have made several live-edge benches recently. The two-inch thick tops (elm or locust so far) have mortises to receive the legs. One bench has four legs, others have boards for legs, with a semi-circle cut out at bottom. The last step in finishing the benches is to put them on a level surface to see if they rock back and forth. In spite of careful construction some do rock a bit, maybe 1/16 to 1/8 inch. So I trim off one leg so that I the bench stands solidly on the floor.
Much to my surprise, a few days later, the benches, again, rock back and forth a bit. Temperature in my wood heated shop and RH cause the benchtops to twist a bit, and that changes the legs. Not much can be done about it. Now I'm wondering what to tell to a buyer about a solidly-built bench that seems unstable.

[MichaelMouse]

I have made several live-edge benches recently. The two-inch thick tops (elm or locust so far) have mortises to receive the legs. One bench has four legs, others have boards for legs, with a semi-circle cut out at bottom. The last step in finishing the benches is to put them on a level surface to see if they rock back and forth. In spite of careful construction some do rock a bit, maybe 1/16 to 1/8 inch. So I trim off one leg so that I the bench stands solidly on the floor.
     Much to my surprise, a few days later, the benches, again,  rock back and forth a bit. Temperature in my wood heated shop and RH cause the benchtops to twist a bit, and that changes the legs. Not much can be done about it. Now I'm wondering what to tell to a buyer about a solidly-built bench that seems unstable.

Tell the buyer that their floor may not be level either, and use some levelers as "feet" appropriate to the floor covering.  Remind them that nature may alter the situation with the seasons.  

Finish the undersides of the bench with a few slow uptake coats, not just the tops.

NB:  Three legs will always sit without rocking.

[FS7]

I have made several live-edge benches recently. The two-inch thick tops (elm or locust so far) have mortises to receive the legs. One bench has four legs, others have boards for legs, with a semi-circle cut out at bottom. The last step in finishing the benches is to put them on a level surface to see if they rock back and forth. In spite of careful construction some do rock a bit, maybe 1/16 to 1/8 inch. So I trim off one leg so that I the bench stands solidly on the floor.
     Much to my surprise, a few days later, the benches, again,  rock back and forth a bit. Temperature in my wood heated shop and RH cause the benchtops to twist a bit, and that changes the legs. Not much can be done about it. Now I'm wondering what to tell to a buyer about a solidly-built bench that seems unstable.

Short of a three-legged solution, almost anything will rock at some point - either because the floor isn't level (almost none are) or because of seasonal humidity changes.

Crushable pads (silicone, felt, or even rubber) help on the smaller error margins (1/16" or less). Larger than that, use threaded inserts and adjustable levelers. You generally need them on almost anything that won't be on carpet.

[MartyRA]

Pretty much tell the truth about the nature of wood and how it expands and contracts with the changes in the weather. 
You could tell them you're still waiting for approval for god-like powers, but that would require a really hard sell tactic and may not be entirely honest..

[Bibliophile 13]

Very good advice here. Pads for feet are always a good idea anyway, and they do help with tiny irregularities. Eventually the bench will come to equilibrium and pretty much stop trying to twist (it will still move a little seasonally), but floors will never be perfectly level.

[KingwoodFan1989]

Short of a three-legged solution, almost anything will rock at some point - either because the floor isn't level (almost none are) or because of seasonal humidity changes.

Crushable pads (silicone, felt, or even rubber) help on the smaller error margins (1/16" or less). Larger than that, use threaded inserts and adjustable levelers. You generally need them on almost anything that won't be on carpet.

^This.
  I've seen other nice furniture before with those leveling pads on it, so there's no shame in using them. You can't stop wood movement 100%.

[mr_skittle]

Hopefully any buyer of a live edge pieces can appreciate the natural inclination of wood to move. I recently built a bench similar to what you've done but with a glued up seat. It also has through mortises and breadboard ends. After painstakingly flattening the top and getting the through mortises level, it took less than a week in the house before the mortises were sitting proud by a little more than a fingernail catch and the seat had substantially shrunk into the breadboard ends. While it is a little annoying, I'll just want till summer and it'll be a different story. I am happy to report that I've not had any problems with rocking. Perhaps the flexibility of the joinery helps with that.

[AHill]

Chris Schwarz made one of his benches out of a pretty thick cherry slab.  Several years after he made it, he blogged that it was starting to crack.  It's the nature of a large, thick slab, I think.

[mr_skittle]

Chris Schwarz made one of his benches out of a pretty thick cherry slab.  Several years after he made it, he blogged that it was starting to crack.  It's the nature of a large, thick slab, I think.

Seems like a job for an inlaid bow tie spline. It's never too late to add one right?

[MKepke]

I think pads are always a good idea..not only does it help with levelling, it helps avoid scratched floors.

Another approach would be to build the base and top as two independent assemblies and use a flexible/loose connection to couple them together. For example:

* figure 8 clips
* tenons in over-sized mortises with gravity holding the top in place

Each assembly can move independently and its movement is absorbed by the flexible/loose connection.

It doesn't solve the uneven floor problem tho.

-Mark