[Quinn Dunki] Makes A Screw Shortener Fit For Kings

February 16, 2025 by Elliot Williams 46 Comments

It’s common problem when you’re building anything with screws: this one is too long, this one is too short. While she can’t teach you how to fix the latter, [Quinn Dunki] has made herself an absolutely deluxe screw shortening jig. And while that’s cool and all, the real value here is the journey; watching over [Quinn]’s shoulders while she’s in the machine shop is always illuminating.

First off, she starts with her old jig, which frankly makes us want one. It’s a short piece of aluminum angle stock with threaded holes in it. You thread the screw in as far as you want, and use the edge as a cutting guide. Very nice!

But aluminum threads wear out quickly so it works if you’re shortening dozens of screws, but gets wonky when you need to cut hundreds. The new jig is made out of steel, and has a slit that clamps the threads in place so she doesn’t have to hold the tiny screws with her other hand while sawing.

This video is, on the surface, about making an improved tool out of steel. But it’s the tips along the way that make it worth your watch. For instance “deburr early and often” is a recurring leitmotif here: it keeps the extra bits that form along any cut from messing up edge finding or vise registration. And yeah, she deburrs after every operation.

There are mistakes, and lessons learned along the way. We’re not going to spoil it all. But in the end, it’s a sweet tool that we’ve never seen before.

If you haven’t read [Quinn]’s series on machine tools that she wrote for us, it’s a treasure trove of machining wisdom.

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Lathe And Laser Team Up To Make Cutting Gear Teeth Easier

February 14, 2025 by Dan Maloney 23 Comments

Fair warning: watching this hybrid manufacturing method for gear teeth may result in an uncontrollable urge to buy a fiber laser cutter. Hackaday isn’t responsible for any financial difficulties that may result.

With that out of the way, this is an interesting look into how traditional machining and desktop manufacturing methods can combine to make parts easier than either method alone. The part that [Paul] is trying to make is called a Hirth coupling, a term that you might not be familiar with (we weren’t) but you’ve likely seen and used. They’re essentially flat surfaces with gear teeth cut into them allowing the two halves of the coupling to nest together and lock firmly in a variety of relative radial positions. They’re commonly used on camera gear like tripods for adjustable control handles and tilt heads, in which case they’re called rosettes.

To make his rosettes, [Paul] started with a block of aluminum on the lathe, where the basic cylindrical shape of the coupling was created. At this point, forming the teeth in the face of each coupling half with traditional machining methods would have been tricky, either using a dividing head on a milling machine or letting a CNC mill have at it. Instead, he fixtured each half of the coupling to the bed of his 100 W fiber laser cutter to cut the teeth. The resulting teeth would probably not be suitable for power transmission; the surface finish was a bit rough, and the tooth gullet was a little too rounded. But for a rosette, this was perfectly acceptable, and probably a lot faster to produce than the alternative.

In case you’re curious as to what [Paul] needs these joints for, it’s a tablet stand for his exercise machine. Sound familiar? That’s because we recently covered his attempts to beef up 3D prints with a metal endoskeleton for the same project.

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Ball Nut Modification Charts A Middle Course Between Building And Buying

December 29, 2024 by Dan Maloney 7 Comments

A lot of the projects we feature here on Hackaday engender the classic “build versus buy” argument. We’ve always been puzzled by that; if anyone can appreciate the sheer joy of making something rather than buying it, it should be our readers. But there’s something to be said for buying the stuff you can buy and concentrating your effort on the bespoke aspects of the project. It’s perhaps not as exciting, but needs must, oftentimes.

Let’s not forget there’s a third way though, which [Andy] explores with this ball nut modification project. Keen-eyed readers will recall [Andy]’s recent scratch-built ball screw build, in service of some top-secret, hush-hush project related to world domination and total subjugation of humanity. His homebrew efforts in this regard were a great lesson in how to machine a complex mechanism to work in a constrained space. Still, it left folks wondering why he’d go to all the trouble when he could have just trimmed an off-the-shelf part down to size. So, he decided to give that a try.

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Rolling Your Own Ball Screws

December 4, 2024 by Dan Maloney 24 Comments

We’ve got mixed feelings about a new video from [AndysMachines] that details how he makes custom ball screws. On the one hand, there’s almost zero chance that we’ll ever have an opportunity to put this information to practical use. But on the other hand, the video gives a fantastic look at the inner workings and design considerations for ball screws, which is worth the price of admission alone

The story behind these ball screws is that [Andy] is apparently in cahoots with SkyNet and is building a T-800 Terminator of his own. Whatever, we don’t judge, but the build requires a short-throw linear drive mechanism that can be back-driven, specs that argue for a ball screw. [Andy] goes through the challenges of building such a thing, which mainly involve creating threads with a deep profile and wide pitch. The screw itself wasn’t too hard to cut, although there were some interesting practical details in the thread profile that we’d never heard of before.

The mating nut was another. Rather than try to cut deep internal threads, [Andy] took a sort of “open-face sandwich” approach, creating half-nuts in a single piece of brass using a CNC machine and a ball-nose mill. The threads were completed by cutting the two halves apart and bolting them together — very clever! [Andy] also showed how the balls recirculate in the nut through channels cut into one of the half-nuts.

Whether the results were worth the effort is up to [Andy], but we were just glad to be along for the ride. And if you want a little more detail on lead screws and ball screws, we’ve got just the article for that.

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Man holding brass bar stock with several polygons turned on end

Polygons On A Lathe

November 3, 2024 by Anne Ogborn 16 Comments

Most professionals would put a polygon on the end of a turned part using a milling machine. But many a hobbyist doesn’t have a mill. And if the polygon needs to be accurately centered, remounting the stock costs accuracy.

[Mehamozg] demonstrates you can turn a polygon on a lathe.

Polygons on shaft ends are surprisingly common, whether you are replacing a lost chuck key, need an angular index, or need a dismountable drive. As the video shows, you can definitely make them on the lathe.

But how the heck does this work? It seems like magic.

Lets start by imagining we disengage and lock the rotating cutter in [Mehamozg]’s setup and run the lathe. If the tool is pointed directly at the center we are just turning normally. If we angle the tool either side of center we still get a cylinder, but the radius increases by the sin of the angle.

Now, if we take a piece of stock with a flat on it and plot radius versus angle we get a flat line with a sin curve dip in it. So if we use [Mehamozg]s setup and run the cutter and chuck at the same speed, the cutter angle and the stock angle increase at the same time, and we end up with a flat on the part. If the cutter is rotating an even multiple of the chuck speed, we get a polygon.

The rub in all this is the cutter angle.. At first we were convinced it was varying enormously. But the surface at the contact point is not perpendicular to the radius from center to contact. So it cancels out, we think. But our brains are a bit fried by this one. Opinions in the comments welcomed.

We like this hack. It’s for a commonly needed operation, and versatile enough to be worth fiddling with the inevitable pain of doing it the first time. For a much more specialized machining hack, check out this tool that works much the same in the other axis.

Machining Copper From Algaecide

August 18, 2024 by Al Williams 5 Comments

We love it when we find someone on the Internet who has the exact same problem we do and then solves it. [Hyperspace Pirate] starts a recent video by saying, “Oh no! I need to get rid of the algae in my pond, but I bought too much algaecide. If only there were a way to turn all this excess into CNC machined parts.” OK, we’ll admit that we don’t actually have this problem, but maybe you do?

Algaecide is typically made with copper sulfate. There are several ways to extract the copper, and while it is a little more expensive than buying copper, it is cost-competitive. Electrolysis works, but it takes a lot of power and time. Instead, he puts a more reactive metal in the liquid to generate a different sulfate, and the copper should precipitate out.

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Categorizing Steel

August 18, 2024 by Al Williams 24 Comments

In the movie Conan the Barbarian, we hear a great deal about “the riddle of steel.” We are never told exactly what that riddle is, but in modern times, it might be: What’s the difference between 4150 and 1020 steel? If you’ve been around a machine shop, you’ve probably heard the AISI/SAE numbers, but if you didn’t know what they mean, [Jason Lonon] can help. The video below covers what the grade numbers mean in detail.

The four digits are actually two separate two-digit numbers. Sometimes, there will be five digits, in which case it is a two-digit number followed by a three-digit number. The first two digits tell you the actual type of steel. For example, 10 is ordinary steel, while 41 is chromium molybdenum steel. The last two or three digits indicate how much carbon is in the steel. If that number is, say, 40, then the steel contains approximately 0.40% carbon.

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