Jatoba and Aluminum Coffee Table

My machinist friend Brian and I collaborated on a coffee table for his new place. I ended up reusing the table top from a previous project - the

Lathe Table

.

The as built dimensions are roughly 24" wide by 48" long and 18" tall. The table top is 1-1/2" thick (8/4 repurposed wood planed to 1.540" thick) and the total weight is about 80 pounds; jatoba is ridiculously heavy. These are the process and final photos.

Initial drawings for the aluminum legs. The idea is for the pins to expand by driving  wooden wedges into the slots similar to how an axe or hammer handle is attached.

Orthographic drawings done in Rhino and Illustrator.

This is the shop drawing. The pins are drafted slightly at the top so they exert enough pressure to hold the leg in place. I need to acquire a photo of his notepad - Brian turned this drawing into what I assume is essentially a G-code equation for the EDM machine.

These next few images are the mock-up leg that Brian produced.

The wedge that gets pounded in is made of jatoba. It's about twice as hard as oak and 1/3 more dense.

Testing the ability of the wedge to expand the aluminum pins.

It worked but in the end the pins got longer, thinner, and drafted (thicker at the top) to provide more ability to expand outwards.

Repurposing the old table top.

Bye bye bad craft.

End grain doesn't glue up well so I added some simple splines. It also lines up the wood better so that you don't waste as much material in the planer.

I added a domino joint (mortise and tenon) just because.

The symbols on there indicate which way the wood bows towards. There wasn't much at all, but if you put opposing pieces next to one another they straighten each other out. The planar I use is 18" wide so I had to glue it up in portions...

... then join the whole thing. I messed up and made the domino joints prior to planing so the sides were off by 1/32" or so. That would require a lot of sanding so later I cut the whole thing in half and did it again.

Cutting the ends flush. The table saw blade has gunk on it from architecture students making models with odd material, lots of not entirely dry glue, and pushing material too quickly/slowly through the saw. More finishing work...

Dual end grain spline joint.

The router fitted with a follow bit; it's essentially a bearing at the tip of the bit that follows a template.

Cutting the ends flush. The shop is used by students so all the blades have gunk on them which leads to burns on harder woods, so - more finishing work.

This one turned out well. The first one was difficult though. 1-1/2" of extremely hard wood is a lot to take off at once.

The material I used for the template was too thin and poor quality so my router bit crushed it a bit and my mortises came out about 15-18 thousands too large - which actually turned out to be okay.

This is a Domino machine made by Festool. They're about $1,000 new... really want one. You can build anything with one of these.

These are the beechwood (similar to oak) tenons that along with glue join two pieces of wood.

This is the result of me cutting the table in half to line up the two halves more closely; it worked out really well.

Re-gluing...

Almost perfectly flush this time.

The corners had to be hand chiseled out to be made square.

I had to flip it over so that the final cuts wouldn't cause tear out on the bottom. This led to cutting 32 (4x4x2) corners square.

This is the EDM (electrical discharge machining) my friend Brian used to cut the tops of the legs... to within "roughly" 100,000th of an inch. (The next seven photos are Brian's).

End milling a taper to the legs. They start out as 2" by 1-1/8" by 18" tall and at the base they're 1-1/8" square.

Just under 0.251", not bad.

The pins are about 1-1/2" long and vary in thickness from 3/32" to 1/8".

I used epoxy on the tops of the legs just to make sure nothing would move then pounded the wedges in. I was very surprised by how well it all worked. They went in easily, flush, and when you grab the legs it's obvious that they're very sturdily attached.

Flush cutting the wedges. I did a first finish coat for some dumb reason... the saw and general mess screwed up the finish so I had to strip and start again.

After stripping and sanding I use a scraper as the final finishing tool. At this angle you can see what it does to the grain. It sort of compresses the grain and leaves it smoother than any sandpaper can.

Since the table will see daily use I opted for a polyurethane finish. Not my favorite but it does protect well. The first three coats were glossy (to bring out the depth of the grain) and the final coat was semi-gloss so that it doesn't look like plastic. I rub it on with a rag, wait 24 hours between coats, lightly sand with 320 grit between coats, and the final finish gets a #0000 steel wooling.

Detail shot of the top of the leg.

Finishing the legs took forever.

Glue and grim...

I ended up putting a coat of poly on the legs so they wouldn't soak in oil from peoples hands.

All the final shots were taken in Crown Hall.

This is a rendering to show how the legs work.