Stopping A Bench Grinder Quickly

In every workshop ever, there’s a power tool that goes unnoticed. It’s the bench grinder. It’s useful when you need it, and completely invisible when you don’t. We take the bench grinder for granted, in part because we keep it over there with that box of oily rags, and partly because it’s so unassuming.

But you can really mess your hands up on a bench grinder. Words like ‘degloving’ are thrown around, and that doesn’t involve actual gloves. For his Hackaday Prize entry, [Scott] is adding safety to the ubiquitous bench grinder. It’s called the Grinder Minder, and it aims to make the humble bench grinder a lot safer.

There are a few goals to the Grinder Minder, most importantly is DC injection braking. This stops the grinder from spinning, and if you’ve ever turned off a bench grinder and waited for it to spin down, you know there’s either a lot of energy in a grinder wheel. Grinder Minder also adds accidental restart protection and an actual ANSI-compliant emergency stop. All of this is designed so that’s it’s a direct drop-in electronics package for a standard off-the-shelf grinder.

The early prototypes for the Grinder Minder have the requisite MOSFETs and gigantic wire-wound resistors , but the team has recently hit an impasse. The current market research tells them the best way forward is designing a product for bigger, more powerful tools that use three-phase power. The team is currently researching what this means for their project, and we’re looking forward to seeing where that research lands them.

Simple Jig Uses Electromagnet For Clean Angle Grinder Cuts

We like it when hacks are literal hack jobs, put together with what’s on hand to do a specific job. This quick and dirty angle grinder circle cutter certainly fills the bill, and makes decent cuts in sheet metal to boot.

The build starts with an unlikely source for parts – an old automotive AC compressor. The one that [Made in Poland] chose to sacrifice was particularly nasty and greasy, but after popping off the pulley, the treasure within was revealed: the large, ring-shaped clutch electromagnet. Liberated from the compressor, the electromagnet was attached to a small frame holding a pillow block. That acts as an axis for an adjustable-length arm, the other end of which holds a modified angle grinder. In use, the electromagnet is powered up by a small 12-volt power supply, fixing the jig in place on the stock. The angle grinder is traced around and makes a surprisingly clean cut. Check out the build and the tool in use in the video below.

At the time [Made in Poland] recorded the video, he noted that he did not have a plasma cutter. That appears to have changed lately, so perhaps he’ll swap out the angle grinder for plasma. And maybe he’ll motorize it for even smoother cuts.

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Bolt-Together Belt Grinder For The No-Weld Shop

Belt grinding offers a lot of advantages for the metalworker, and since belt grinders are pretty simple machines, shop-built tools are not an uncommon project. A bolt-together belt grinder makes this tool even more accessible to the home gamer.

With no access to a welder but with a basic milling machine and an ample scrap bin at his disposal,  [IJustLikeMakingThings] had to get creative and modify some of the welding-required belt grinder designs he found online to be bolt-up builds.  The key to a cool running belt grinder is for the belt to be as long as possible, and the 2″x72″ belt seems to be the sweet spot, at least here in the States. Machined drive and idler wheels with the crown needed for proper belt tracking were sourced online, as was the D-bracket for holding the two guide wheels. But the rest of the parts were fabricated with simple tools and bolted together. [IJustLikeMakingThings] provides a lot of detail in his write-up, and it shouldn’t be too hard to build a belt grinder just like this one.

Looking for other belt grinder plans to compare notes? Here’s a grinder with an even simpler design, but with welding required.

Magnet Implants, Your Cyborg Primer

What would you do to gain a sixth sense? Some of us would submit to a minor surgical procedure where a magnet is implanted under the skin. While this isn’t the first time magnet implants have been mentioned here on Hackaday, [The Thought Emporium] did a phenomenal job of gathering the scattered data from blogs, forum posts, and personal experimentation into a short video which can be seen after the break.

As [The Thought Emporium] explains in more eloquent detail, a magnet under the skin allows the implantee to gain a permanent sense of strong magnetic fields. Implantation in a fingertip is most common because nerve density is high and probing is possible. Ear implants are the next most useful because oscillating magnetic fields can be translated to sound.

For some, this is merely a parlor trick. Lifting paper clips and messing with a compass are great fun. Can magnet implants be more than whimsical baubles?

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It’s An Angle Grinder! No, It’s A Floor Sander!

Faced with the potentially arduous task of sanding a wood floor, what would you do? Hire a pro? Rent the proper tools and do it yourself? Perhaps even shell out big bucks to buy professional grade tools? Or would you root around in your junk pile and slap together a quick and dirty floor sander from an old angle grinder?

That’s what [Donn DIY] did when looking at the wide expanse of fresh floorboards in his new sauna. Never one to take the easy way out, and apparently with a thing for angled gear boxes, [Donn DIY] took the guts out of a burnt-out angle grinder for his impromptu floor sander. A drill attached to the old motor rotor provides the spin, and a couple of pieces of scrap wood make the platen. Sandpaper strips are clamped between the discs, and as seen in the video below, the whole contraption does an admirable job.

We’ve seen lots of angle grinder hacks before, some useful, some silly. This one gets the job done and is a nice quick hack that speaks to the value of a well-stocked junk pile.

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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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An Extremely Useful Shop-Built Belt Grinder

What’s green and black and used all over the shop? It’s [Make It Extreme]’s newest build, a scratch-built belt grinder. And as usual, the build video gets us in the mood to cut metal.

We’ll go out on a limb here and state that the lathe, and not the belt grinder, is the essential metalworking tool. That’s pretty clear from this build – the running gear is machined entirely on a lathe. But as central as the lathe is to machinery making, belt grinders like this one have to rate right up there in terms of shop utility.

You can sharpen with them, quickly remove stock, clean up welds, form chamfers, and remove rust and corrosion. They’re great all-around tools, and with the quick-release idler feature that this one has, fast belt changes for different jobs make it even more flexible. We’d like to see more adjustability in the work table – the ability to angle the table relative to the belt is very handy – but in all this is a great build and a nice tool to have.

On top of it all, watching the [Make It Extreme] builds – like this sandblaster, spot welder, or belt sander – is like high-speed shop class. There’s a lot to learn, although we have to admit that welding in shorts and a T-shirt gives us the willies.

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