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I plan to build a coffee table following plans in Fine Woodworking. In the article, the author uses a plywood top, but I already have solid lumber that I'd like to use.

Table top with perpendicular rails Source: me, based on plans in Fine Woodworking #242

The author of the article simply screws the cross rails (blue) to the top (yellow), but for a solid top this is not ideal.

How can I attach these rails to the table top in a way that allows the wood to shrink and expand with changes in humidity?

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  • screw would be fine, they compensate better for cross expansion – ratchet freak Apr 7 '15 at 20:41
  • Why not come up with the opposite design: Use stretchers that run the length of the table instead of running perpendicular? The stretchers are essentially hidden anyway. – user2720 Sep 18 '16 at 6:17
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You can use screws, but in a slightly different manner. Instead of simply pre-drilling a hole and screwing the screw, you can use a router to create a slot with a countersink or counterbore bit.

Counter sink and bore slotting bit

Source: LeeValley

This slot will allow wood movement of your solid top while staying securely attached on your cross rails.

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    Very nice. I believe I could even replicate those bits with a narrow straight bit and either a wider straight bit, or a V-groove bit. – lars Apr 7 '15 at 21:16
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    You can still have a fixed screw at one point on the rails. This is a good answer for other attachment points on the rails. (I would put a fixed screw in the center and expanding screws on the ends). – saltface Apr 7 '15 at 21:17
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Tabletops are often attached to the frame and aprons using tabletop fasteners such as these, which allow for some wood movement:

tabletop fasteners

(Source)

This is what they look like installed:

tabletop fasteners installed

(Source)

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    Wow. It took some looking to get the orientation of the bottom, "installed", picture correct. We're looking at the underside of the table (where the screws are) and the inside of the support rail. The solid pieces of the clip go into a grove in the rail, allowing them to slide with expansion. – FreeMan Mar 17 '16 at 15:57
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The wood in your top will expand and contract in one direction, while the cross braces will expand and contract perpendicular to that.

There are a couple of different products and techniques that would help.

For a set of rails like the ones in your picture, consider 'figure 8' fasteners.

Figure 8

https://www.leevalley.com/US/Garden/page.aspx?p=50311&cat=3,41306,41312&ap=1

You create a shallow depression with a forstner bit or similar on the rail top, such that the figure eight fastener can rotate a bit when screwed down (not extremely tight, but not loose either.) These allow expansion in two directions if done correctly.

Another option are oval washers like these:

Oval

https://www.leevalley.com/en/hardware/page.aspx?cat=3,41306,41309&p=40940

They allow expansion in one direction.

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  • Given that the wood expands in different directions, I feel the figure 8 fasteners are the best option. The slot fasteners described in this answer and elsewhere won't work for both directions of expansion. – Adam Davis Apr 8 '15 at 17:45

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