Monday, July 18, 2016

In my spare time over the past few months, in between other projects, I decided to build a coffee table for my apartment.  I found a few concrete tables that look cool, but decided to build my own.

Here is the plan.  I ended up making it 18" overall, but the look should be similar.

To make the mold for the concrete top, I used a sheet of melamine.  I am pouring it upside down, so the smooth mold surface will become the table top.

I backed up the melamine walls with 2x4s so they remain perpendicular under the outward pressure of the concrete.

In order to seal the mold and add a radius to the top corners of the table, I ran a bead of silicone caulk around the perimeter.  In order to get a crisp consistent edge, I masked it first. I also made a steel tool, shown here in the foreground, to get a consistent 1/8" radius in the caulking.

Next I prepared to pour the concrete.  I am using Quickrete Countertop Mix, specially formulated for this type of thing.

What a damn mess.  This part of the process reminded me of why I prefer working with metal!

I also added some wire rebar, not shown, and tack welded some 3/8-16 weld-nuts into the structure.  This will allow me to bolt the tabletop to the stainless steel legs.

Speaking of stainless steel, I'm now at the fun part!  I bought a bunch of 18ga 304 stainless steel tubing to use for the legs.

After marking the tubes, I cut everything with a grinder and 4-1/2" cutting disc, then did the final trim to my scribe lines using a belt sander with a ceramic 80 grit belt.

Everything is cut!

I wanted to add threaded inserts to the bottom of the table so I could use it on hard floors.  Right now my apartment is carpeted, so I decided to recess the inserts so the threads don't get caught in the carpeting if I want to slide it around.  I made a dimple die and formed them in a 20-ton press.

After dimpling, I welded a stainless steel nut to the inside.

In order to get both legs exactly the same, I tacked up a steel fixture to keep everything square.  I added some 0.020" stainless steel shims to one side so I can pull the parts out since it's captured on all four sides.

Next steps: welding and finishing!

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