Head to Head Push Bolt

M5 and M6 bolts symbiosis

Refining the push bolt

In a previous episode, we 3D printed a push bolt as a cap on top of an M6 bolt, and the cap is effectively a peg to hold the ring where the tension comes together.

I thought it might be more interesting to see how I can have something more sophisticated than a simple peg on the push bolt.

I decided that it would be good to have another option to screw something tight to the end of the push bolt, so I had the idea to 3D print a coupling between two bolts.

design-un der

3D design

I set upon designing a shape which could hold the two bolts together head-to-head in the right way.

The little M5 bolt will go through the hole and have its head nested nicely into an M5 shaped indentation.

To hold on to the M6 bolt head, another hexagonal shaped indentation is needed at the bottom.

design-un der

Above you should be able to see where the M5 and M6 bolt heads are supposed to be held.


The top of the shape is a nicely rounded form which hides both bolt heads.

Putting it together

The idea is to first insert the little M5 bolt, and then later insert the M5 head, to create the new push bolt. As an extra, I got some nice cap nuts.


It takes a few ticks with a hammer. I drilled a hole in a piece of wood so that I could hammer against the plastic shape rather than against bolts.

First, with the bolt inserted, I set it up so that I could give the bolt a tick or two to get it to settle properly in its hole.


After a little hammering, the M5 bolt fits snugly inside the shape.


Finished phase one.


Now for the M6 bolt, which can be easily ticked into place so that it rests on the head of the M5 bolt and fits snugly into its hole.


With both bolts hammered snugly into the nice rounded shape, we’re basically finished


This allows for using the big bolt to tighten up the tensegrity, but it also provides a nice small bolt pointing outwards to hold the ring and whatever else.


This looks very nice!

The big bolt needs only one nut now (used to be two) to tighten against the aluminum tubes to effectively lengthen the bars, in the true pretenst tradition.


The new design allows me to nicely top off the push bolt with a cap nut!

Time to think about what else might be done with this outward-pointing M5 bolt.

Pretenst Constructions:

2022-06-22: "Head to Head Push Bolt": M5 and M6 bolts symbiosis
2022-05-30: "Hiding Knots": bump up the aesthetics
2022-05-25: "Innovation with 3D Printer": the push bolt
2021-12-02: "Headless Hug": breaking a rule for the sake of symmetry
2021-10-28: "Rebuilding the Halo": finally got it right
2021-10-20: "Convergence": growing and reconnecting
2021-07-27: "120-Strut Brass Bubble": taking the next step up in complexity
2021-05-26: "30-Strut Brass Bubble": bouncing spherical tensegrity
2021-04-08: "Bow Tie Tensegrity": better bend resistance
2021-03-29: "Six Twist Essential": what if more hands could see?!
2021-01-25: "Minimal Tensegrity": no more tension lines than absolutely necessary
2021-01-18: "Degrees of Freedom": first adjustable hybrid tensegrity
2021-01-11: "Fractal Experiment": a tensegrity of tensegrities
2020-12-09: "Axial Tension": pretensing what is already pretenst
2020-11-02: "Halo by Crane - Part 2": the strengthening
2020-10-26: "Halo by Crane - Part 1": assembly complete but strength lacking
2020-10-12: "Brass and Tulips": a tight and strong tensegrity tower
2020-08-10: "Prefab Tension Tower": the tower of eight twists
2020-07-27: "Elastic Bubble": building with elastic ease
2020-07-13: "The Twist Sisters": left-handed and right-handed
2020-07-06: "Radial Tension": Pulling towards the middle
2020-06-22: "Diamond of Tension": Four pulls for every push
2020-06-15: "Prefab Tension": Separating compression from tension


2021-03-10: "Do the Twist": constructing in push-pull space
2021-03-01: "Elastic Interval Geometry": pure pairwise push and pull