A Common Thread — oxblog
Around the middle of 2019, I started making the equipment around me speak one<br>electrical language. I built a USB Power Delivery sink controller, then<br>converted more and more of my<br>equipment to USB-C. The point was not the connector itself. It was being<br>able to reach for one cable and one power supply with some confidence that<br>things would work together.
Quite by accident, I have done the same thing mechanically. The interface is<br>the ordinary camera tripod thread: 1/4″-20 UNC. Once I noticed the absurd<br>range of clamps, ball heads, quick-release plates and articulating arms built<br>around it, I stopped treating them as camera equipment. They are a mature box<br>of mechanical parts that happen to have escaped from photography.
No camera in sight. An arm keeps my cup within reach without consuming a<br>surface.
A mechanical USB-C
The smaller camera thread has a nominal 1/4-inch diameter and 20 threads per<br>inch in the Unified National Coarse series. Together with the larger 3/8″-16<br>thread, it is specified by ISO 1222 for connecting cameras, tripods and accessories.<br>The interesting part is everything that followed: decades of compatible gear<br>designed to hold a load, put it at a useful angle and stay there.
That ecosystem is far more useful to me than another bespoke bracket. A new<br>project only needs to expose the thread. I can then choose an existing arm,<br>clamp or plate, change it later, or borrow a part from another setup without<br>redesigning the object.
A 1/4″-20 socket gives the LaserPecker LP1 access to the same ecosystem.
My laptop platform is another endpoint. The stand beneath it can be replaced<br>without changing the platform.
Drill, then tap
Converting an existing object is wonderfully uneventful. In material thick<br>enough to hold a useful thread, I drill the appropriate tapping-size hole and<br>run a 1/4″-20 UNC tap through it. Drilling makes the hole; tapping is<br>the term for cutting the internal thread. In thin or brittle material, a<br>threaded insert or a through-bolt is the honest solution instead.
The luckiest conversion was an IKEA STÄNKREGN LED ring lamp (005.421.54).<br>Its proprietary pivot hole was already exactly the right size. I removed the<br>original stand and screwed a camera mount into the plastic, cutting the thread<br>as it went. It looks as if it was designed for the little tripod, although<br>neither manufacturer had the other in mind.
The STÄNKREGN on a small tabletop tripod, with no adapter in between.
The original pivot became a camera-mount socket. Tom appears to approve.
The missing constraint
The plain thread has one irritating weakness: it is also an axis. An<br>off-centre load applies torque around the screw, so a heavy light or long arm<br>has to be tightened hard enough for friction alone to stop it rotating. That<br>works, until it doesn’t.
Then I found the refinement I had been missing: a 1/4″-20 locating screw with<br>two retractable anti-twist pins, commonly described as ARRI locating pins.<br>The SmallRig arm I use calls them exactly that.<br>On a plain surface the pins retract and the ordinary screw still works. Give<br>them two matching holes, however, and the screw supplies the clamping force<br>while the pins take the torque.
The centre screw pulls the parts together; the two spring-loaded pins stop<br>them rotating.
The matching socket is still an ordinary 1/4″-20 mount, with two small holes<br>added for the locating pins.
Once I understood the arrangement, I added the two locating holes to the<br>mounts I had already made. This is a particularly nice extension: old and new<br>parts remain compatible, but parts that know about the extra holes get a much<br>stronger connection.
Once everything speaks the same language
The camera catalogue now supplies the joints for my lights. A compact panel<br>can sit beside or above the laptop, then move out of the way with one lever.
A clamp, an articulating arm and a small LED panel become a desk light.
From above: the same arm puts the light exactly where the work needs it.
The same parts scale to a much larger LED panel. The light, arm and cabinet<br>clamp remain separate, replaceable objects; the thread is the only agreement<br>between them.
The back of the larger light: clamp, ball head, 1/4″-20 socket and USB-C<br>power.
The useful side of the same panel.
Foresight without prophecy
I love a simple design that remains useful far beyond anything its makers<br>could have predicted. That is not luck. Luck was the hole in the IKEA light.<br>Foresight is putting just enough constraint into an interface that<br>people can adapt it with confidence, while leaving paths open for uses and<br>improvements that do not exist yet.
The camera industry did not need to foresee my cup holder, laptop platform or<br>apartment lighting. It only had to hold a diameter, a thread pitch and a mating<br>surface steady for long enough that an ecosystem could compound around them.<br>Later, two optional holes improved the connection without invalidating the<br>original one. That is excellent...