Reverse Engineering Bottle Threads For Fun And Profit

Recently, one of [Eric]’s clients asked him to design a bottle. Simple enough for a product designer, except that the client needed it to thread into a specific type of cap. And no, they don’t know the specs.

But that’s no problem, thought [Eric] as he turned on the exhaust fan and reached for the secret ingredient that would make casting the negative image of the threads a breeze. He mixed up the foul-smelling body filler with the requisite hardener and some lovely cyan toner powder and packed it into the cap with a tongue depressor. Then he capped off the cast by adding a small PVC collar to lengthen the cast so he has something to grab on to when it’s time to take it out.

Bondo does seem like a good choice for casting threads. You need something workable enough to twist out of there without breaking, but rigid enough that the small detail of the threads isn’t lost. For the release agent, [Eric] used Johnson’s Paste Wax. He notes from experience that it works particularly well with Bondo, and even seems to help it cure.

Once the Bondo hardened, [Eric] made sure it screwed in and out of the cap and then moved on to CAD modeling and 3D printing bottle prototypes until he was satisfied. We’ve got the video screwed in after the break to cap things off.

Did you know that you can also use toner powder to tint your epoxy resin? Just remember that it is particulate matter, and take precautions.

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Mechanisms: The Screw Thread

They hold together everything from the most delicate watch to the largest bridge. The world is literally kept from coming apart by screws and bolts, and yet we don’t often give a thought to these mechanisms. Part of that is probably because we’ve gotten so good at making them that they’re seen as cheap commodities, but the physics and engineering behind the screw thread is interesting stuff.

We all likely remember an early science lesson wherein the basic building blocks of all mechanisms laid out. The simple machines are mechanisms that use an applied force to do work, such as the inclined plane, the lever, and the pulley. For instance, an inclined plane, in the form of a splitting wedge, directs the force of blows against its flat face into a chunk of wood, forcing the wood apart.

Screw threads are another simple machine, and can be thought of as a long, gently sloped inclined plane wrapped around a cylinder. Cut a long right triangle out of paper, wrap it around a pencil starting at the big end, and the hypotenuse forms a helical ramp that looks just like a thread. Of course, for a screw thread to do any work, it has to project out more than the thickness of a piece of paper, and the shape of the projection determines the mechanical properties of the screw.

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Simple Shop-made Taps For Threading Wood

Wood can be the material of choice for many kinds of projects, but it often falls out of the running in favor of metal or plastic if it needs to take a threaded fastener. But with a little ingenuity you can make your own wood taps and cut threads that will perform great.

Making wood do things that wood isn’t supposed to do is [Matthias Wandel]’s thing. Hackers the world over know and use his wood gears designer to lay out gears for all kinds of projects from musical marble machines to a wooden Antikythera mechanism. Woodworkers have been threading wood for centuries , so making wood take a decent thread isn’t exactly something new. But doing it on the cheap and making the threads clean and solid has always been tricky. The video after the break shows [Matthias]’ method of cutting a tap out of an ordinary threaded rod or even off-the-shelf lag screws. He uses a simple jig to hold the blank so that flutes can be cut with an angle grinder. The taps work well in the materials he tested, and a little informal stress testing at the end of the video shows promise for long service life of the threads.

Wood threads aren’t suitable for every project, but knowing that you can do it might just open the path to a quick, easy build. This is a great tip to keep in mind.

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Turning Television Into A Simple Tapestry

Teleknitting, the brainchild of Moscow artist [vtol], is an interesting project. On one hand, it doesn’t knit anything that is useful in a traditional sense, but on the other, it attempts the complex task of deconstructing broadcasted media into a simpler form of information transmission.

Teleknitting’s three main components are the processing and display block — made up of the antenna, Android tablet, and speaker — the dyeing machine with its ink, sponges, actuators, and Arduino Uno, and the rotating platform for the sacrificial object. A program running on the tablet analyzes the received signal and — as displayed on its screen — gradually halves the number of pixels in the image until there is only one left with a basic representation of the picture’s colour. From there, thread passes over five sponges which dye it the appropriate colour, with an armature that responds to the broadcast’s volume directing where the thread will bind the object.

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Arduino Sketch: The Next Generation

What was your first Arduino program? Probably an LED blinker — that seems to be the “hello world” of microcontrolllers. You probably moved on to things a little more complicated pretty quickly. At some point, things get harder because the Arduino lacks an operating system.

There are operating systems that will run on the Arduino. They aren’t full-featured like Windows or Linux, but they allow you to run multiple tasks that are both isolated from each other (to some degree) and have a way to cooperate (that is, synchronize, share data and resources, and so on). One such operating system is ChibiOS. It will run on AVR- and ARM-based devices. You can find documentation about the entire project on the home page along with other ports.

The problem with adopting a new operating system is always getting started. [ItKindaWorks] has started a video series on using ChibiOS and has posted three installments so far (see below; one is about getting started, the other two cover messaging, mutexes, and priorities).

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Custom Threaded Inserts For 3D Printing

There’s a variety of ways to add threaded holes to 3D printed objects. You can tap a hole, but the plastic isn’t always strong enough. Nut traps work, but aren’t very attractive and can be difficult to get exactly the right size. If you try to enclose them, you have to add a manual step to your printing process, too. You can buy threaded inserts (see video below) but that means some other piece of hardware to have to stock in your shop.

[PeterM13] had a different idea: Cut a piece of threaded stock, put nuts on the end and heat it up to let the nuts reform the plastic. This way the nut traps wind up the perfect size by definition. He used two nuts aligned and secured with thread locker. Then he used a hot air gun to only heat the metal (so as to reduce the chance of deforming the actual part). Once it was hot (about 15 seconds) he pulled the nuts into the open hole, where it melted the plastic which grips the nuts once cooled again.

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How To Zip, Stick, And Screw Stuff Together

One of the first problems every new hacker/maker must solve is this: What’s the best way to attach part “A” to part “B”. We all have our go-to solutions. Hot glue, duck tape ( “duct tape” if you prefer) or maybe even zip ties. Super glue, epoxy, and if we’re feeling extra MacGyver-ish then it’s time for some bubble gum. For some Hackaday readers, this stuff will seem like old hat, but for a beginner it can be a source of much frustration. Even well versed hackers might pick up a few handy tips and tricks presented in this video after the break.

In part one of this series, [Ben Krasnow] shows us the proper use of just a few of the tools and techniques he uses in his shop. [Ben] starts out with a zip-tie tool which he loves in part because of a tension setting that ensures it’s tight but not overly. He moves on to advice for adhesive-vs-material and some tips on using threaded fasteners in several different circumstances. He also included a list of the parts and tools he uses so you don’t have to go hunting them down.

[Ben] is no stranger to us here at Hackaday. He does some epic science video. You can subscribe to his channel or follow his blog if you enjoy what you see.

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