A Delicate Tea Table

Hard Maple

This maple tea table was inspired by a metal version I found on the web.  

I remembered I had a maple panel.  It was a bit thicker than 3/4".  19" x 14".  Room enough to cut four 3" strips from that were 19" long. Glued them together to make a 3" x 3" x 19" block I used to make the center post from:

Center post 

Mounted on my radial axis. First step was to turn the square block into a 3" cylinder. 

18 inches of 3"d cylinder

Then the roughing cut, which pointed out a few flaws in my setup. The square section left next to the 3-jaw chuck didn't care to run into the router chuck as it created a burning smell and left the router chuck black with carbon. 

I made a finish pass down the cylinder to cut the desired shape.  A few visible flaws left from the roughing cut that went haywire. I took the post from the CNC out to my garage lathe to clean up and sand. 

For the base I glued up some maple boards.  They were a bit thinner than 1.5" thick. When the glue was dry I scraped off what squeezed out, then used my drum sander to clean off and flatten both sides.

Uniformly flat, clamped to my CNC bridges, and getting the bottom cove cut out.

Cove cut.  Almost done.

Board flipped over, new file loaded, and the top surface was cut. Next to the bandsaw to cut off the corners.  After that a trip to my trim router table to flush trim the bottom edge, then round over the bottom edge just a little (1/8"r). 

Base trimmed and cleaned up.  Post trying it on for size.

A good snug fit. 

Next came the top for this table. A thin edge is desired. It would help the structure to be thicker in the middle where the post connects.  Made an intermediate plate that glues and screws to the post, but then can be screwed to the bottom of the table top.  I ordered some 3/4" thick maple strips I can glue up to make the top from. 

Maple to make the top arrived. Strips 2" wide, 3/4" thick, and 16" long. The strips were square and smooth and  ready to glue together. 

Some advice to minimize the chance of bowing after the slats are glued up, is to alternate the end grain curves on each piece. 

Once all the strip are glued together and the surface cleaned up a trip or two through my drum sander smoothed out any offsets and made both sides uniformly parallel to each other. 

Next was clamping the panel down to my CNC and cutting the bottom contour.  The hub was cut first.  Left on the CNC to check that the center post top tenon does fit in the mortise in the center.  Wisely done, as it didn't fit the first time tried.  A new CNC file was made and run to cut the mortise wider.  With fit verified the contour shape was cut.  Then the part was remove from the CNC and cut free from the starting block using my bandsaw. 

The top underside shape took the longest to cut and created a beautiful huge mess of fine maple chips.  

The only deficiency of this design is that from above where most will see it the contours under the top are not visible.

Simple thin edge.

This table will get a maple stain to even out the color of all the board strips. I don't drink tea, so am not sure where this table will end up.  😉

As I study the aesthetic details, the simple top seems naked compared to the post and base below.  My first addition is a 30 degree bevel around the perimeter.  To accomplish that required a fixture with bearings to add to my trim router table fence.

Bearings to keep the edge from getting too close to the bit. 

No room for a bearing to run on the edge. 

Beveled edge.

Comments welcomed and Encouraged!

4D

 

Small table and a white pipe.

In an effort to use up materials I've collected over the years, this project employed a section of white painted pipe as the structural post of a small table. The table top I made awhile back as a challenge to use up scraps of short lengths of wood.  Scraps ripped and tipped and glued together to make a roughly 10" x 10" panel, then CNC cut into an interesting shape and bottom contour. 

The top needed some structure to hold it horizontally above the floor.  18 to 24 inches tall was the desired height I wanted the table to be. I have at least 3 identical section of white pipe.  One pipe alone made for a simple design.  I just needed to come up with a structural way to connect it to the top and a base that spreads out the load so the table wouldn't easily tip over. 

Connecting wood to metal pipe was the challenge. I deformed the end of the pipe to a shape that wouldn't spin in a pocket.  I chose a hexagon for the end cross section.  I had to CNC cut a negative form to press the pipe into using my bench vise.  

Round to Hex over 2 inches

1" thick HDPE I have on hand, so I cut forms from it. High density was the desired quality.  I didn't want a form that the steel would deform before the form could reshape the steel.  

HDPE worked.  

With a way to reshape the pipe ends, making a pocket for the hex ends came next. To hold the pipe between table top and base I ran a length of 1/4-20 all-thread through the pipe. I used a cap nut on the top and a nylock nut on the bottom end.  The bottom nut will be under the base and not seen.  The top cap nut is decorative, flush, and in the center of the top. The pipe runs straight up from base to top.   

It took two tries to cut a pocket that the ends of the pipe would slide into.  I checked the fit while the board was still on my CNC.  Next step was to simply enlarged the vectors used, recalculated the toolpaths and cut again. I had a 1 degree taper on the sides of the hex hole, and although the pipe can be drawn in I fear the board may split.  I replaced the initial block making a new one with a simple pocket with straight sides. 

A simple base design came next.

The center wood block has a board on each side. The boards extend to be the feet of the table.  The boards half-lap/interlock to surround the center block. 

Base slat with slots

I designed a wedging half lap joint cut with a CNC, and used it in assembling the 4 base boards.  A spline in two sides of the block and two of the surrounding wood slats will structurally keep it in place. Glue will do the rest. 

 

Base slat edge refined

To refine the edges of the base boards I drew a curve that when intersecting each board would be 3 degrees from horizontal.  Knowing I had a 3 degree tapered router bit I then cut the curves using that bit. Look close at the base of the table in this photo and you'll see the crisscross pattern curves all blend together. 

Now that all parts are made and assembly is verified, It is time to put some stain and top finish on the base boards and the table top.

I'll add a photo here when I have the table stained and finished.

Comments and questions always welcomed,

4D

Pseudo Tensegrity End Table

Held stable with only tension straps.

Most tensegrity projects have a rigidly connected post up from the base and another that projects down from the top.  They are connected by a simple tension cable. An unstable connection.  To stabilize this usually 4 more cables run from top to bottom at the outer corners. The end result is barely stable.  An unexpected side push will usually collapse such a table. 

My project starts with a rigid post that is not attached structurally to either the top or the bottom.  An unstable assembly. Both ends are rounded over and sit in a slippery socket at the top and bottom centers. The center post is threaded.  Right hand threads on one end and left hand threads on the other.   

Bottom and top of the center post rounded over.

Screw holes patched with walnut plugs.

Holes repaired

The ball ends of the post rest in sockets cut in HDPE that inset into the bottom of the table top and top of the base. 

Socket test.

A good fit.  Post spins easily in the slippery socket.

Hub nuts screw onto the post. They have slots around their edge. Webbing straps will slip into the slots and be pinned in place with a 5mm pin though a grommet in their end. 

With both RH and LH threaded hub nuts, a twist of the post will tighten or loosen the straps. I cut the threads using the threading toolpath available in Vectric.com's Aspire software and a side cutting V bit. I hook the straps to the underside of the top and the hubs in a slot with a pin dropped in a hole or slot.  The pin passes through a grommet in the ends of the straps.  The straps end in a slot perpendicular to the pin. 5mm x 5/8" steel pins.

Strap connection to hub nut.

Shelf pins pin the strap end in place.  I made a friction fit hole for the shelf pins so they fit snuggly and will not drop out easily.  It took some test holes to find the best size of drill bit to use.  A #9 drill bit provided the closest fit. 

The top has 4 perimeter slots for straps, and an inset HDPE section with a ball socket cut in the middle.  Socket test seen above.   

Underside of the table top.

The key to this project is how the straps are connected to make the project work. 

The non-threaded section of the post is where you grasp the post to twist it.  It might be easier to grasp and twist if it's shape was a hexagon or octagon cross section.  

For detail continuity the base is a scaled down version of the top. The contoured surface is on its top rather than its bottom. 

Base

I made both top and bottom inserts from some 1" thick HDPE I have, re-sawn to just under 3/4" thick, then milled down to 5/8" thick on my CNC. 

Socket inserts for the top and base.

A  test assembly.  Straps were installed with the nut lower on the post.  Once attached the post was twisted to lift the hub nut higher to tension the straps. 

Repeated for the top.

Repeat the straps and hub on the other end to hold the table top securely horizontal.

Making straps for the design I've realize matching strap sets is a hit or miss problem. It is easy to make two or more the same length.  As those in the long axis aren't the same length as those in the short direction, and all have to be a precise length to tighten up at the same time. Finding the length of a set to go with the other set is the challenge.  Making and installing the set for the long direction would be easier if they could be adjusted in length after installing.  Change them from being a fixed length with a grommet in both ends to an adjustable length with a grommet in one end. The other end wrapping around something to come back and attach to itself.  The attachment point should be adjustable to change the total length of the strap.  Something I'll look into should I use straps in future projects. 

The wood parts of this table need some final sanding and a finish applied.  I like tung oil on walnut.  This table does provide an interesting glance down at the base while in use.  More interesting than any typical table. It was an enjoyable exercise to design and build. 

Straps in tension make a stable assembly.

4D

 

Unfolding Flat Pack Coffee Table Design

Unfolded

This design is loosely based on a folding workbench table I came up with 20ish years back. Reduced in scale and revised in detail the table is 16" high when unfolded, 42 inches long, and 15 inches deep. Folded up it is the same length and depth but flat and 2.25" thick. No tools are needed to erect it from it's folded state or to fold it back to its flat state. The base consists of two leg panels that aren't attached to the top, two flipping panels that are attached to the top end of the legs and the top, and two diagonal braces that attach to the top and near the center of the leg panels. A twist lever locks the flipping panels to the top when the table is unfolded.  This is so the table can be picked up without wanting to start folding. 

Underside View

For the folding action to work a precise connection point between leg panels and braces must be found. Through some iterative drafting steps I've been able to get within .001" of where it is. To fold flat both the leg panels and the braces have an offset end. The leg panels are one inch narrower than the  table top.  The flip panels and braces are tucked under the top to minimize their visual impact on the stance of the table. 

Leg Panels

Flip Panels and Braces

When folding up the flip panels flip over and out of the way so the braces can lay down flat against the top. 

Folded flat.

The pivoting connections are the only challenge left to resolve.  The flip panels connect/pivot from the top underside and have to flip 180 degrees over where they connect.  The braces connect to both the underside of the top and near the center of the leg panels. Some clearance between pivoting parts and where they pivot from is needed to prevent wood from rubbing against wood as they pivot. 1/8" (3mm) Baltic birch plywood could be used as the pivot brackets extending from the bottom face of the table top.  Glued into a slot they would be a challenge to remove/replace if they ever fail though. Plate brass or aluminum could be used but would need a mechanical connection into the table top.  This connection deserves an original design solution. 

The leg panels have openings for the flip panel and the braces.  Making each leg from three sections assembled to capture the other parts would be the obvious strategy.  I need a way to mechanically do this so they can be taken apart should any piece fail. My intersecting binding bolt trick I used on the last two TV tray tables might work.  I'd like to figure out a way to have the action of bolting them in also snug the joint tight. Some sort of cam or lever action. There is a double end cam solution already out there used for knock-down furniture that might work.   

It wouldn't take much to modify the geometry to side table dimensions. Longer legs and a shorter top might require one leg to fold over the other to keep the folded length within the length of the top.   

My house is overrun with coffee tables so I doubt I'll ever build this design. It is parked here for future reference so I can clear the idea from my mind and let it fill up with newer ideas. 

Innovative TV Tray Table. Maple. 4th Variation

Maple with a maple stain.

This version, made from maple hardwood, uses an original outer leg design but retains the upgraded details from the previous versions.  

Three other versions:

Cherry

Red Oak

White Ash

Shown with the top flat and level above, the design inverts when you flip the top and pull the top stretcher through.  Once inverted the geometry leaves the top slanted down with a projecting ledge at the bottom. 

Slanted Top

This leg line runs straight from the table top connection down to the floor.  The offset that makes the dual geometry work is done at the pivot point between outer and inner legs. A more direct line and simpler detail than the legs on the previous versions.  While this version also folds up minimally 2" thick for storage or shipping, it looks unique compared to the 3 other versions when folded flat. 

Folded Flat. 2" Thick

Outer legs bolt to the top and inner leg frame. On my Cherry version I came up with a pivot pin that gets trapped in place by an intersecting binding bolt shaft.  The legs and bolts can pivot freely but won't loosen,  They won't come out unless the binding bolt is removed. I used that same strategy in this Maple version. 

Pivot pins.

Center Pivot Point

Upper Rear Corner

I'll confess that hard maple put up a fight during the process of turning it into a TV tray table.  Look close at this prototype and you will see a few war wound scars.  Not all wood from Maple trees is the same. I recommend southern soft maple rather than northern hard maple if you want to make your own from maple.  I've used a mix of both in this prototype.  I threw in a strip of red oak to define the front edge.  The ledge strip on the slanted side is Bubinga. 

This Maple version has a single webbing strap between the center of the top's back edge and the top stretcher. The strap runs from stretcher to rear center edge of the top, folds over, then back to the stretcher. An intersecting binding bolt pierces a grommet in the fold of the strap to hold it in the slot. The 60 degree triangle helps reduce any chance for the inner leg frame to rack. Using strap it is wise to make sure they don't wrap over any sharp corners/edges.  This is the slot cut in the back edge of the maple table top for the strap:

Smooth edges for the strap to wrap over.

The strap runs from the top's back edge directly into the stretcher when in the flat position. In the slanted position the strap runs over then into the stretcher. Binding bolts pass through grommets in the ends and center fold of the strap to hold them in their slots. The angled strap helps keep the frame from racking. 

Strap Connections

Iteration.  There are several variations of details that can be made that utilize the same geometry of my patented idea. Within each the path to finding a great visual composition is done in steps.  What may seem fine in 2D elevation views of a design may not seem as cohesive in detail with the whole composition when viewed on a 3D standing prototype.  Willingness to refine a detail before finalizing the build is a useful quality to possess.  That was the case with this detail:

Original "bump". 

You can see my sketched alternative idea on the top leg.  The original bump to surround this critical offset bolt hole was an unpleasant visual distraction when I first assembled this table. A fat point on a svelte frame. As the legs could be easily removed and returned to my CNC bed I had the CNC recut this area of the legs. 

Svelte Frame

This design is patented. The details can vary, but the geometry that lets the table stand flat or turn inside out to be slanted down is the unique property.

 

For information on licensing the design please contact:

Sarah Nolting
Licensing Associate
Kansas State University Innovation Partners
(785) 532-3910
snolting@ksu.edu
www.k-state.edu/innovation-partners

 

    

TV Tray Table. Cherry. Refinement in Details.

Cherry.  5i

This is my 3rd TV Tray Table prototype.  Made from Cherry wood.  It demonstrates different details used with the same dual position geometry that the first two have.  Those two are here:

Ash Version

Red Oak Version

Ash, Cherry, Red Oak

The first two use threaded bolts into embedded nuts or barrel nuts to hold the outer legs to the top and the inner leg frame. They could come unscrewed in use as the frame is folded and unfolded. This Cherry wood version addresses that flaw and uses a new detail.  The bolt heads look the same but won't come unscrewed in use.

Pivot Bolts

The bolts pictured above are the pivot bolts for the outer leg connection to the top and inner leg frame. They slip through a hole in the outer leg and into the top's rear corners, or the inner leg frame sides. They are held there by an intersecting binding screw shaft. They can spin in place but won't unscrew themselves as the table folds or unfolds.  I was unable to find such a thing looking online, so I cut these from longer bolts using the rotary axis on my CNC. 

Binding Bolts.  18mm Shafts

I've used different strategies to tension the frame so it won't collapse.  Wire cable on the Ash version, and straps at the top in the Oak version are both complicated to make/install.  This Cherry wood version uses short 3/4" wide straps between the front and back legs. They are 5" below the pivot point to keep the legs from splitting apart.  The unique use and path of the straps adapts to both slanted and inside-out horizontal top positions. The strap location is just below where the top rests when the stand is folded up flat. A little serendipity in what was an arbitrary location choice. 

Folded Flat

The outer legs of this Cherry wood version run straight, with only a small bump over to the offset hole at the top.  A simple detail that might draw some attention.  The bump is neatly in plane with the slanted top.  

Slanted top

It is an interesting bump above the top when horizontal. 

Horizontal top.

This Cherry version uses a simple short strap with a grommet in both ends to handle the tension when the legs want to split apart. 

Grommet in strap end.

A binding bolt passes through the grommet inside each leg to retain the straps but lets the strap rotate to accommodate the angle it approaches each leg at. The straps slip into 1/8" wide slots. One edge of the slot is rounded over so the edge won't wear on the strap as it exits and wraps around the leg to head toward the other leg. 

Straps held by binding bolts

This Cherry table is so far my favorite of the three. Beautiful wood. Complimentary green straps. A pleasant presence. 

This design is patented. The details can vary, but the geometry that lets the table stand flat or turn inside out to be slanted down is the unique property. A fourth version, made from maple, can be found HERE.

 

For information on licensing the design please contact:

Sarah Nolting
Licensing Associate
Kansas State University Innovation Partners
(785) 532-3910
snolting@ksu.edu
www.k-state.edu/innovation-partners

Questions and comments are welcomed!

4D