In Chris Schwarz Blog, Woodworking Blogs

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I recently finished building an Enzo Mari table from the 1970s as part of an article for Popular Woodworking Magazine, and I have only one worry about the project.

It looks great. It feels stout. But I’m worried that the joinery might not last forever.

The joinery? Lots of properly installed wood screws, with diagonal bracing to reduce or eliminate racking. But screws can come loose and might allow the table’s base to rack.

While you could build the table with mortise-and-tenon joints, that wasn’t the intent of Mari the designer. The table is supposed to be easy enough for a beginner to make with simple tools.

Clench nails ready to be driven against the steel plate. Note the angle of the nails.

After some thought, I think that “clenched nails” might be the answer.

Clenched nails hold together some of the oldest pieces of woodworking extant today, including doors that still function quite well. The trick to using the nail is it is driven through the two boards you want to join and its tip is bent or turned over like a fish hook back into the backside of the lower board.

Turn the joint over and you can see the tips of the nails bent over back into the board.

Clenching locks the two pieces together and the joint can last 1,000 years or so.

When I clench nails, I drive the nail through the boards at an angle with a steel plate below the boards. The angle helps the nail’s tip bounce off the steel and turn back into the wood. The angle also allows the tip of the nail to clench across the grain of the lower board, strengthening the joint even further.

Three wire nails bent like this when I tried to clench them. The sunk nail is a clench nail.

A Bright Idea?
I’ve clenched a lot of nails in my life, but I’ve always used special “clench nails” from Tremont that bend easily and properly. I decided to see if standard bright wire nails from the home center would clench.

Long story short: I didn’t have any success. After varying the angle several times I found that the wire nails simply bent under the head every time. Clench nails have a thickened shank that prevents them from crumpling.

Try it for yourself, but I’m going to go back to my clench nails for this operation.

After much abuse, the wood failed before the nails would pull loose.

After assembling a few sample joints from the Mari table I tried to pull them apart. The wood failed before the fasteners came loose.

That’s a good joint.

— Christopher Schwarz

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