Threaded post, radial cut

[4DThinker]

Render of the underside of the table top. 

Socket in the center for the top of the post.  Actually to be cut in an inset piece of HDPE.  Slots near each edge for the straps. 

4D

[Grandpadave52]

Very cool design 4D. While most of the technical stuff is beyond my skillets, enjoy following this along.

[4DThinker]

Cut  test socket for the ends of the post to make sure I had a good fit and the cut would be smooth enough. Knew HDPE would cut easily.

Fit is good. Post feels like it is setting in something very slippery.  Easy to twist.

This was a 1" thick scrap and the socket was cut 5/8" deep.  I've ordered some 5/8" thick HDPE so I'll reduce the socket depth to 1/2" in the final pieces that inset into the table top and base. 

4D

 

[DuckSoup]

This is cool!

[4DThinker]

Projects like this are both a curse and a pleasure of mine after 4 decades of both designing and making my own furniture and teaching that topic to creative design college students.  The curse is that my house doesn't need any more furniture.  The pleasure is that I have all the tools I need to realize my ideas as they pop into my mind. This is one of those wild ideas. A starting idea that as many do is already leading to/feeding other potential furniture design ideas.   

4D

[4DThinker]

Took most of the morning to cut the top of the table out.  The underside is where all the details are.

Moulding toolpath to contour the underside shape.  Pocket to make an area for the HDPE block where post will socket into.  Profile cuts to cut the  perimeter slots for straps.  Another moulding toolpath to round over the inner edge of the slots where straps will wrap over. Final profile toolpath to cut the perimeter shape.  

 

Some sanding to do to smooth out the ridges left by the 1/4" ball nosed bit as it contoured the top face.  I'll likely round over the top and bottom edges with a 1/8" radius round over bit.  Could have done the bottom edge while it was clamped on the CNC but didn't think of it then.  Board was 15/16" thick and tapers down to 5/8" on the outer edge.  This was some claro walnut I bought from a California dealer.  Been staring at it for more than a year.

Now I need to finalize the design and make the base of this table. 

[4DThinker]

Came to the conclusion that the base, for detail continuity, will be a scaled down version of the top.  Only difference other size is that the contoured surface will be on its top rather on the bottom.  Had a left over section of the same claro walnut the top was cut from to make the bottom from.  The 1/2" thick HDMI I ordered for the socket insets won't be here until Wednesday.  Tomorrow I'll work on making the straps.  Also had a vision that by playing with the strap lengths I could have it lean a bit (maybe 10 degrees max) in the long dimension yet still be level. Might make for a more interesting aesthetic stance. 

4D

[4DThinker]

Put my CNC to work this early morning to cut out the base for this project.  A baby version of the top essentially.

 

I kind of wish I had an automatic tool changer.  First to contour the surface a 3/16" ball nosed bit using the moulding toolpath. Second a 1/8" end mill and a profile toolpath on the line to cut the slots.  Third bit and toolpath was a 1/8" ball nosed bit and the moulding toolpath to round over the inner edges of the slots. Last bit change to a 3/16" spiral upcut end mill to both pocket out the center for the HDPE insert, and profile cut the perimeter.   The initial moulding toolpath to contour the top took 5x times longer to cut than all the other toolpaths together. 

4D

[4DThinker]

5/8" thick HDPE sheet arrived.   Had to send it back as it was less than .6" thick.  Closer to 15mm. Grrrrrr..  Already have 5/8" deep pockets made to inset it into. 

[Grandpadave52]

Sorry about the HDPE snafu. That walnut is beautiful.

[4DThinker]

8 hours ago, Grandpadave52 said:

Sorry about the HDPE snafu. That walnut is beautiful.

Thanks.  I've given up trying to find 5/8" thick HDPE on the web. Either a supplier doesn't carry it, or they want 2 arms and one leg for a 12 x 12 piece. I've got some that is 1" thick, so I cut a 7"x3"  piece of it, sliced it down to a rough 3/4" thick using my band saw, and will pocket it to a perfect 5/8" thick before cutting the sockets and shapes out.

I'll cut these out this morning after breakfast. 

[4DThinker]

Got the two socket insets cut.  Surprised how well they fit.  Photo is the underside of the table top.  Realized that if I pushed the inset all the way in I'd never get it out so here it is just set in about 3/8" of the 5/8" thickness. 

I was planning on using two screws to hold each inset in, but given how well they fit, and that the post will hold them in when the straps have it in compression they can't come out.   The bottom piece is now on my CNC waiting for pin slots to be cut on its bottom.  The pins will hold the straps in their slots when they are in tension. 

4D 

Edited December 11, 2024 by 4DThinker

[4DThinker]

Quick proof-of-concept test.  Old strap rejects from my TV tray table designs.    Installed the easily with the nut lower, then twisted the post to draw the straps tight.

HDPE socket let the post twist freely.  Post held perpendicular in one axis, but obviously needs straps in the other direction to completely stabilize it. 

Now to make tighter fitting walnut hubs to replace the oak prototypes.  That and more straps. 

4D

[DuckSoup]

 The HDPE looks like it was poured into the walnut

[4DThinker]

2 minutes ago, DuckSoup said:

 The HDPE looks like it was poured into the walnut

Not sure what temp it melts at, but it was easy to get a good fit using my CNC and the same vector for the pocket as I used to cut out the HDPE inset.  Fit on the base is just loose enough that it'll slide out if held upside down.  The fit on the top is nearly air-tight as even slipping it in half way I could feel pressure. 

4D 

[Grandpadave52]

This just keeps get more interesting and intriguing. Way outside of my pay grade but doesn't keep me from away.

[Grandpadave52]

2 minutes ago, 4DThinker said:

Fit on the base is just loose enough that it'll slide out if held upside down.

Would double sided tape be a viable solution?

[4DThinker]

1 minute ago, Grandpadave52 said:

This just keeps get more interesting and intriguing. Way outside of my pay grade but doesn't keep me from away.

My pay grade from teaching was the lowest in my department for teachers the same rank.  No respect for my engineering/architecture aptitude that helped students realize their impossible designs for 4.5 decades.  Shoulda coulda been an engineer I suppose.  Fun I'll admit, but not a career to get rich with. 

[4DThinker]

6 minutes ago, Grandpadave52 said:

Would double sided tape be a viable solution?

No real need to make it tighter or stay stuck in the pocket.  The post pressing down on it as the straps get tighter will never let it slip out. 

4D

[4DThinker]

Making straps to complete the build I've found that since the top and bottom are longer that they are wide, that getting the straps made so all 4 tension up at the same time is a picky challenge.  It took me 3 tries to get 4 straps to work with the base.  Started thinking that some math should tell me how long a set should be if I knew the length/width ratio of the base and the length of one direction set of straps.  Nope.  With all straps in place it looked like my new set were 3/4" too long.  Cut 3/4" off them only to find then too short to with with the other set.  Made one more set, a wild guess, and got lucky to find all got tight at the same time as the post twisted. 

 

What this tells me is that an ideal solution would have a way to adjust the strap length after installing it. Rather than pinning both ends, perhaps pinning one, then on the other end wrapping over/around something to fold back where it could clasp to itself anywhere along it's length.   Some research into strap adjustment hardware is due. 

4D