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Mini Tetrahedral Tensegrity Table #9: Finishing the Disks and Attaching the Pyramids

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Blog entry by Ron Stewart posted 03-26-2022 09:36 PM 521 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 8: Disk Details--Attaching the Outer Support Wires Part 9 of Mini Tetrahedral Tensegrity Table series Part 10: Tensioning the Wires and Completing the Project »

I wanted to use glue to attach the pyramids to the disks, because I didn’t want any visible fasteners. But it was very apparent that I would need something to help precisely position the pyramids and prevent them from shifting during glue up. I decided to use tiny alignment pins/holes.

I went back to my trusty disk template, marked the inside edges of the pyramid, and drilled 1/16” center holes.

To drill matching holes in a pyramid, I clamped it to the template.

Then I drilled the holes from below, making sure not to drill too deep.

That worked well.

For alignment pins, I could have cut short lengths of brad nails. But I’m a woodworker, so I fashioned
the pins from toothpicks. The toothpicks were too thick for the holes, but I chucked them in a drill
and spun them through sandpaper to reduce their diameter. Then I used my side cutters to cut them to
length. They weren’t pretty, but they were good enough.

Now all I had to do was drill matching holes in the disks. My template made that easy, and in just a few seconds I had drilled three perfectly spaced holes in the bottom disk… in the wrong locations. Idiot! The pockets for the tensioning wire pockets had to be aligned, but not the pyramids. The alignment holes in the two disks needed to be rotated 60-degrees relative to each other.

I drilled three new holes in the correct location, and pulled out some sandpaper. I had to fill the unwanted holes with a sawdust/glue mixture.

At this point, I didn’t trust myself not to fill in the good holes, so I taped over them.

Each bad hole was in a location with a different color shade, and one was right beside a dark grain line, so I had to create light and dark sawdust.

It worked out okay. I think some of my patch lifted when I did my final sanding (or I didn’t add enough filler), because I can still see dimples in the finished table, but I don’t really notice them unless I look for them.

After a final sanding and easing of edges, the disks were ready to finish. I wanted to darken the walnut a bit and warm up some of its grayness, so I tested a few finishes.

Brown dye (with one coat of Arm-R-Seal) was too dark and a bit muddy. (The piece on the right is unfinished.)

Zar Rosewood stain (plus one coat of Arm-R-Seal) looked pretty good, but maybe a bit too dark in spots.

The only other possible finish I had was an ancient can of Zinsser amber shellac. It looked really nice. It warmed up the walnut, didn’t darken it too much, and it made the the wood glow. I decided to use it like a stain (wiping most of it off) with a gloss Arm-R-Seal topcoat. Gloss felt right for this project, and I thought it would show reflections of the pyramids, adding visual interest.

Before applying the shellac and poly, I had to mask off the pyramid base. I used 1/4” strips of painters tape for that.

I applied the shellac “stain.”

Then I added three coats of Arm-R-Seal poly.

Because of the alignment pins, gluing on the pyramids was easy and drama-free.

Now I was ready for the final step: attaching and tensioning the wires.

-- Ron Stewart



4 comments so far

View Dave Polaschek's profile (online now)

Dave Polaschek

10483 posts in 2074 days


#1 posted 03-26-2022 09:57 PM

When I have to fill something and can’t quite match the color, I’ll use a fine-point brush with a little garnet shellac (I always have shellac mixed up in my shop) and darken with that. I can even, on a good-day, paint in lines to look like grain.

Looking good, but then I know how the story ends. ;-)

-- Dave - Santa Fe

View Ron Stewart's profile

Ron Stewart

399 posts in 3995 days


#2 posted 03-27-2022 12:17 AM

That’s a handy tip.

I guess you mix your own shellac. I’ve never tried that. I usually have a can of spray shellac on hand. I’m lucky I had the amber shellac. It was so old that a few pinholes had opened (rusted through?) the base and had made a real mess of the shelf. I had put the can upside down in a plastic tub we use to hold things to take to the hazardous waste disposal facility (probably unnecessary for shellac now that I think of it). It’s probably something like a 10-pound cut. :-)

-- Ron Stewart

View Dave Polaschek's profile (online now)

Dave Polaschek

10483 posts in 2074 days


#3 posted 03-27-2022 02:42 AM

Most commercial stuff is 2-3# cut. But yeah, I buy flakes from Shellac Shack and alcohol from the hardware store and generally mix about a 1.5# cut (2 oz of flakes in a 12oz salsa jar topped up with alcohol). Have a little magnetic stirrer that mixes it while I work on something else. I apply it with a pad, rag or a brush, depending on the surface. The best part is “shellac sticks to everything, and everything sticks to shellac” so I never need to think very hard about what I’m finishing with. Plus, shellac with just enough BLO to keep the rag from sticking makes a nice friction finish on the lathe.

-- Dave - Santa Fe

View Ron Stewart's profile

Ron Stewart

399 posts in 3995 days


#4 posted 03-27-2022 04:11 PM

Thanks for the link. I need to experiment with mixing my own and French polishing. I do like shellac when I use it, particularly it’s fast drying time. And I don’t feel like it’s killing brain cells by the millions like lacquer does because of fumes.

I think my can if shellac started out as a 3-pound cut, but it’s at least ten years old, and I’m not sure what’s still in the can… more like a thickish slurry of decayed shellac remnants.

-- Ron Stewart

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