Two goniometers sit on a table. One is an open wooden box with a long piece of plywood along the bottom. A laser distance finder rests on the front edge and a printed angle scale has been attached to the back side of the box. To the right of this box is a much smaller goniometer made from an orange pipe cap with a small strip of paper serving as the angle scale inside the interior edge. It is attached to a wooden handle that looks vaguely like a V. A laser pointer can be inserted from the bottom where a hole has been drilled through the wood.

Goniometer Gives You An Edge At Knife Sharpening

Sometimes you absolutely, positively need to know the angle of the cutting edge on a knife. When you do, the best tool for the job is a laser goniometer, and [Felix Immler] shows us three different ways to build one. (YouTube)

The underlying principle of all three of these builds is to project reflected laser light off a knife blade onto a scale going from 0-45˚. [Immler] shows a basic demonstration of this concept with a hinge toward the beginning of the video (after the break). Blades with multiple bevels will reflect light to each of the appropriate points on the scale.

The simplest version of the tool is a printed PDF scale attached to a wooden box with a hole for the blade to pass through. The next uses a large pipe end cap and a drilled-out piece of wood to create a more manageable measuring tool. Finally, [Immler] worked with a friend to design a 3D printed goniometer with differently-sized adapters to fit a variety of laser pointers.

Now that you’re ready to precisely sharpen your blades, why not sharpen this guacamole bot or try making your own knife from raw ore?

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Heirloom Knife Will Carve Pumpkins For Years To Come

Halloween may be behind us, but that just means that we’ve reached the best time to buy pumpkins. After all, it’s still fall, and there are pies to be made and tables to be decorated. Why should carved-up pumpkins be restricted to spooky season?

The only problem is that it’s 2022, and we’re still expected to use those terrible little serrated knives to carve our pumpkins. Those orange-handled garbage ‘knives’ are hardly suited to cut the lid, much less carve any of the intricate designs that come in the little booklet. So what’s a pumpkin-carving enthusiast to do? If you’re [XYZ Create], you make your own out of walnut, maple, and a gently-used jigsaw blade that’s still way sharp enough to tear through pumpkin flesh.

[XYZ Create] started with a nice chunk of walnut, which he split lengthwise in order to insert the blade, which sits in a cavity within a thin piece of maple. Once [XYZ Create] had the handle ready to go, he inserted the jigsaw blade and epoxied the sandwich together. After sanding down the edges to make a comfortable grip, he finished off the build by rubbing a bit of carving board wax into the handle. Check out the build video after the break.

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The Cheat Way To Perfectly Split An Oreo

Believe it or not, much research has been done in how to perfectly split Oreos with an even amount of cream on both sides. Early studies suggested it simply wasn’t possible, with one side always getting the majority of the cream.  However, [Ian Charnas] has now found a sneaky workaround.

First attempts involved heating in a microwave or chilling the cookies in the freezer. Neither helped in the slightest. A vacuum chamber only served to delaminate the cream from both sides of the cookie entirely, while water jet cutting made an awful mess.

[Ian] ended up realizing that crack propagation could be used to prepare Oreos for a perfect split. A knife was used to score a groove all around the cream layer, right down the middle. The Oreos were then frozen, turning the cream effectively solid. When the Oreo is then twisted, the groove serves as a starting point for a crack that propagates across the surface, splitting the cream neatly between both halves.

[Ian] took things further by building a 3D-printed lathe that grooves Oreos using a sterilized scalpel blade. This allows cookies to be quickly prepped for a perfect split. However, you are left eating frozen Oreos at the end of it, with some sacrifices to freshness.

It’s a neat way to approach the Oreo splitting problem, even if it’s only one step removed from simply using a knife. We’ve seen [Ian]’s work before, too, in the form of the radioactively-powered Game Boy. Video after the break.

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Knife Throwing Machine Gets The Spin Just Right

Despite how it might appear in bad action movies, throwing a knife and making it stick in a target is no easy feat. Taking inspiration from the aforementioned movies, [Quint] and his son built a magazine-fed knife throwing machine, capable of sticking a knife at any distance within its range.

Throwing a sharp piece of metal with a machine isn’t that hard, but timing the spin to hit the target point-first is a real challenge. To achieve this, [Quint] used a pair of high-performance servo motors to drive a pair of parallel timing belts. Mounting a carriage with a rotating knife-holder between the belts allows for a spinning throw by running one belt slightly faster. The carriage slides on a pair of copper rails, which also provide power to the knife holder via a couple of repurposed carbon motor brushes.

At first, the knife holder was an electromagnet, but it couldn’t reliably hold or release the stainless steel throwing knives. This was changed to a solenoid-driven mechanism that locks into slots machined into the knives. Knives are fed automatically from a spring-loaded magazine at the back as long as the trigger is held down, technically making it full-auto. To match the spin rate to the throwing distance, a LIDAR sensor is used to measure the distance, which also adjusts the angle of the aiming laser to compensate for the knife’s trajectory.

The development process was fraught with frustration, failure, and danger. Unreliable knife holders, exploding carriages, and faulty electronics that seemingly fired of their own accord were all challenges that needed to be overcome. However, the result is a machine that can both throw knives and nurture a kid’s passion for building and programming.

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Surgery Robot Is A Real Cut Up

A robot that performs surgery is a serious thing. One bug in the control system could end with disaster. Unless of course, you’re [Michael Reeves], in which case disaster is all part of the fun. (Video, embedded below.)

Taking inspiration from The da Vinci Surgical System, [Michael] set out to build a system that was faster, while still maintaining precision. He created a belt drive gantry system, not unlike many 3D printers, laser cutters, or woodworking CNC machines. Machines like this often use stepper motors. [Michael] decided to go with [Oskar Weigl’s] ODrive and brushless motors instead. The ODrive is on open source controller which turns off the shelf brushless motors — such as those found in R/C planes or hoverboards, into precision industrial servos. Sound familiar? ODrive was an entrant in the 2016 Hackaday Prize. [Michael] was even able to do away the ubiquitous limit switch by monitoring current draw with the ODrive.

It all adds up to a serious build. But this is [Michael “laser eye” Reeves] after all. The video is meant to be entertaining, with a hidden payload of education and inspiration. The fun starts when he arms the robot with a giant kitchen knife and performs “surgery” on a pineapple. If you want to know what happens when mannequins and fake blood enter the picture, then watch the video after the break.

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Preserved Lemons On A Hacker’s Budget

“If you wish to make an apple pie from scratch, you must first invent the universe.” [Carl Sagan]. If you wish to make preserved lemons the same way as [Uri Tuchman], you have to start with that mentality. Video also below. The recipe for [Uri]’s preserved lemons involves two ingredients see sea salt, and sliced lemons, but we don’t expect you came here looking for a recipe and the food is less important than the journey.

Recipes take for granted that we have all the necessary utensils on hand, but what if you are missing one? What if you are missing all of them? Life’s lemons won’t get the best of us, and if we’re utensil-poor and tool-rich we will make those lemons regret trying to take a bite out of us. The first fixture for cutting lemons is a cutting board, then a knife, and finally an airtight container. We see him make all of them from stock material by hand. Does that seem like a lot of work? You forgot that if you’re going to eat up, you’ll need a serving platter and fork. If he ever opens a restaurant, don’t expect it to be fast food.

Maybe humans will only need one tool in the kitchen someday but at least one cat receives food from a single silicone-brained tool.

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3D Printed Knife Sharpening Tool Makes The Job Easy

A sharp knife is a joy to use, but many of us are guilty of buying the cheapest kitchen tools available and rarely maintaining them. Keeping knives sharp is key to working with them both safely and effectively, but to sharpen by hand requires patience and skill. [CNC Kitchen] instead decided to use technology to get around the problem, designing a 3D-printed tool to make the job easy (Youtube video, embedded below).

The knife sharpener is a straightforward build, requiring a few simple 3D printed parts in combination with some nuts, bolts, and aluminum rods. It’s designed to use commonly sized whetstones, which makes procurement easy. The design has undergone refinement over the years, with [CNC Kitchen] adding pockets for the magnets and a spherical bearing which reduces slop in the movement.

[CNC Kitchen] reports that the tool works wonderfully, allowing even a novice to sharpen knives well. Parts are available on Thingiverse for those who wish to print their own. If however, you insist on doing things the old-fashioned way, you can get an electronic coach to help improve your technique. Video after the break.

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