Building a Knife by Hand is just as Hard as you Think

Carl Sagan once said: “If you wish to make an apple pie from scratch, you must first invent the universe.” In other words, the term “scratch” is really a relative sort of thing. Did you grow the apples? Did you plant the wheat to make the flour? Where do you keep your windmill, incidentally? With Carl’s words in mind, we suppose we can’t say that [Flannagill] truly built this incredible knife from scratch, after all, he ordered the sheet steel on Amazon. But we think it’s close enough.

He was kind enough to document the epic build in fantastic detail, including (crucially), the missteps he made along the way. While none of the mistakes were big enough to derail the project, he mentions a few instances where he wasted time and money trying to take shortcuts. Even if making your own knives at home isn’t on your short list of summer projects, we’d wager there’s something in this build log you can learn from regardless.

So how does one build a knife? Slowly and methodically, if what [Flannagill] has written up is any indication. It started with a sketch of the knife on a piece of paper, the outline of which was then transferred to a piece of tool steel with nothing more exotic than a permanent marker. An angle grinder was then used to follow the outline and create the rough shape of the final knife.

From there, the process is done almost entirely with hand files. Here [Flannagill] gives one of his most important pieces of advice: don’t cheap out on the tools. He bought the cheapest set of files he could, and paid the price: he says it took up to 14 hours to complete just one side of the knife. Once he switched over to higher quality files, the rest of the work went much faster.

After filing and sanding the knife blank, it went into a charcoal fire to be hardened, followed by a total of 4 hours in a 200 C (~400 F) oven to heat temper it. Finally the handle pieces (which are officially known as “scales”) were attached, and finished with considerably less labor intensive woodworking methods. The final result is a gorgeous one of a kind specimen that [Flannagill] is rightly very proud of.

If you’re worried this process looks a bit too quick and easy for you, don’t worry. You can always go the [Bil Herd] route and make a forge out of your old sink if you’d rather start your apple pie a bit closer to the tree.

Sharpening with Bluetooth

Few things are as frustrating in the kitchen as a dull knife. [Becky] and her chef friend collaborated to build a Bluetooth module to tell you when you are sharpening a knife at the optimum angle. That might sound a little specialized, but the problem boils down to one that is common enough in a lot of situations: how do you tell your exact orientation while in motion? That is, with the knife moving rapidly back and forth over the sharpening stone, how can you measure the angle of the blade reliably?

Looking for a challenge, [Becky’s] first attempt was to just use an accelerometer. It worked, but it wasn’t very precise. Her final answer turned out to be a full inertial measurement unit — the BNO055 — that combines an accelerometer, a magnetometer, and a gyroscope along with enough smarts to fuse the data into actual position data.

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Fail of the Week: The Little Ultrasonic Knife That Couldn’t

We all know the feeling of an idea that sounded great when it was rattling around in our head, only to disappoint when we actually build the thing. It’s a natural consequence of trying new stuff, and when it happens, we salvage what we can and move on, hopefully in wisdom.

The thing that at least semi-defeated [This Old Tony] was an attempt to build an ultrasonic cutter, and it didn’t go well. Not that any blood was shed in the video below, although there seemed like there would be the way [Old Tony] was handling those X-Acto blades. His basic approach was to harvest the transducer and driver from a cheap ultrasonic cleaner and retask the lot into a tool to vibrate a knife rapidly enough to power it through tough materials with ease.

Spoiler alert: it didn’t work very well. We think the primary issue was using a transducer that was vastly underpowered compared to commercial (and expensive) ultrasonic cutters, but we suspect the horn he machined was probably not optimized either. To be fair, modeling the acoustic performance of something like that isn’t easy, so we can’t expect much. But still, it seems like the cutter could have worked better. Share your thoughts on how to make version 2.0 better in the comments.

The video is longish, but it’s as entertaining as any of [Old Tony]’s videos, and packed full of incidental gems, like the details of cavitation. We enjoyed it, even if the results were suboptimal. If you want to see a [This Old Tony] project that really delivers, check out his beautiful boring head build.

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The Mother of All Belt Grinders

It seems like everyone is building belt grinders these days. You might think [Jeremy Schmidt] is just hoping on the bandwagon, but you’d be wrong. He took a full two years to design the perfect belt grinder for his needs. Now he’s built his perfect beast, and we must say, it’s quite impressive!

[Jeremy] had seen grinders which can tilt, but most of them tilt the entire machine, including the table. He designed his machine with an independent table. This means the belt can be placed at any angle, while the table remains flat. He’s achieved some really interesting finishes with a course grind on a 45-degree angle to the workpiece.

No build is without its problems. In [Jeremy’s] case it was building the box which acts as a receiver for the machine and the tables. Regular square tube stock wasn’t quite rigid enough, so bar stock was the way to go. The first attempt at building the box resulted in a warped tube, due to the stresses of welding. [Jeremy] was more careful the second time, moving from section to section of the four welds. This kept the heat from building up, and the box stayed straight.

The final result is an incredibly rigid machine which definitely will withstand anything that [Jeremy] can throw at it.

If you want to see more belt grinders at work, check out [Bob]’s treadmill belt grinder, or [Mike’s] conversion.

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Knives Hewn from Brake Discs Past

Knives are tools that rely heavily on material quality to do their job right. A knife made of cheap steel won’t hold an edge well, and blunt knives are more likely to cause injury, or at the least, be more difficult to use. The trick to making a good knife is to start with good material. Disc brakes just so happen to be a great source of cast iron, and are readily available, so [Diesineveryfilm Customs] has machined a knife out of a brake disc.

The first step is to roughly cut out the knife’s form from the disc. It’s easy enough to cut out with an angle grinder, following up with a belt sander to finish up the grip. After sharpening, the sharp blade is taped off for safety while a wooden grip is added. Holes are drilled in the brake rotor, allowing the wooden parts to be pinned and glued together before a trip to the belt sander for shaping. A string and dye are added to the handle as finishing touches.

It’s a great use of high-quality scrap material to produce a useful tool. An earlier disc brake knife video shares some useful techniques of its own – we liked the shortcut of measuring the disc thickness, then using a matching drillbit to mark the centerline for sharpening.

Perhaps your own knives aren’t sharp enough – check out this home-built adjustable sharpening rig.

Home-made Adjustable Knife Jig

When sharpening a knife, it is critical to have the knife at the right angle. A knife jig handles this for you, letting you focus on getting the edge right. You could just buy one, but where’s the fun in that? [origamimavin] decided to make his own adjustable knife jig using bits he bought from the hardware store for $27, and which you might have in your junk pile. Fortunately for us, he’s written up the process in excellent detail, explaining the how and why of each step.

He used a couple of tools that you might not have lying around (a bandsaw and a belt sander), but these could be easily replaced with their manual cousins, or your local hackerspace will doubtless provide you access to them. Either way, it’s a simple build which could help your knives keep their clean, sharp edge for years to come.

Arduino Powered Knife-Wielding Tentacle will Leave You in Stitches

Writing articles for Hackaday, we see funny projects, and we see dangerous projects. It’s rare to find a project which combines the two. This one somehow manages to pull it off. [Outaspaceman] is familiar with LittleBits, but he’s just starting to learn Arduino programming. He completed the blink tutorial, but blinking an LED just wasn’t enough fanfare for the success of his first Arduino program. He connected the Arduino Mega’s LED output to a pair of LittleBits which then switch a servo between two positions. A bare servo wouldn’t be much fun, so [Outaspaceman] connected a tentacle and a small Swiss army knife. Yes, a knife.

The tentacle in question is designed to be a finger puppet. There’s something about a tentacle waving a knife around that is so hilarious and absurd that we couldn’t help but laugh. We’re not alone apparently, as this video has gone viral with over 1 million views. It’s almost like a violent revenge of the most useless machine. For the technically curious, the tentacle’s seemingly random motion is analogous to that of the double pendulum.

Our readers will be happy to know that [Outaspaceman] has made it to the Arduino servo tutorial, and is now controlling the servo directly, no LittleBits needed. We just hope he has a good way to turn his creation off – without the need for stitches.

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