Uses for Magnets

**rgsparber** · Jan 2, 2019, 07:03 AM

Originally Posted by bruce.desertrat

I have one of those little round magnets on the top of my drill press, holds the chuck key right there.

A good source of scary strong magnets is old computer hard drives. They're fiddly to disassemble (but you then have a large collection of nice little 4-40 torx 8 screws as well) buy they're very strong and come conveniently (or inconveniently, depending on your needs) attached to a sturdy steel back with pre-drilled mounting holes. The best come out of old 3½" SCSI server grade drives. One I have in our kitchen holds about 30 pages of recipes to the fridge. attached are common examples.from a 2¼" laptop drive, some consumer grade drives and the thick ones are some of those server SCSI drives. You most definitely don't want those bigger ones tocome together at any speed, they shatter into a billion highly magnetic, razor-sharp shards.

I have a few of these wonderful magnets and, yes, they are scary strong. I've gotten a few blood blisters getting in their way.

Have you seen the largest neodynium magnet that K & J sells? It warns people not to buy it unless they really know what they are doing. The 4 inch cube comes in this very thick walled wood box so it doesn't fix itself to the floor of the delivery truck.

Rick

**bobneumann** · Jan 1, 2019, 12:57 PM

At the risk of being slightly off topic: I made my own version of a carriage DRO for my lathe from a stainless 8" digital caliper. One jaw is screwed to a bracket that clamps to the front way. The other jaw hangs out in space when not in use, and attaches very nicely to the carriage with a 13mm neodymium magnet when in use. It's really very snug and tight and reliable, and very easy to attach and detach.

You can see the remnants of JBweld, which I originally had used to attach the magnet to the caliper jaw. But it actually made alignment more difficult, and the magnet sticks to the caliper head so nicely that it's much easier to just leave the magnet on the carriage and stick the caliper head to the magnet.

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**rgsparber** · Jan 2, 2019, 06:59 AM

Couldn't ask for an easier way to get the caliper on and off the lathe. Well done!

Rick

**mklotz** · Jan 2, 2019, 08:45 AM

Those hard disk magnets are probably strong enough to drive a through-the-glass motion transmission device.

Jon showed an example of a magnetic system for washing the outside of glass windows that can't be reached manually. Maybe a device to clear bug smears from the windshield without leaving the car?

A rotary motion transmission could drive a moving display item inside an aquarium without the need to penetrate the glass/plastic.

Laboratories use a stirring system for sealed flasks that consists of a magnet immersed in the fluid rotated by an external field generated in the heating platform on which the flask is placed. I'm not sure how the rotating field is generated; could be done electrically or via a magnet rotated by a motor.

**bruce.desertrat** · Jan 2, 2019, 09:16 AM

The hotplate/stirrers (at least the very common Corning ones) are simply bar magnets attached to a little dc motor; I used them for years in my previous career in chemistry.

**mklotz** · Jan 2, 2019, 10:48 AM

Then there's the whole world of magnetic gears.

An introduction to the subject...

https://hackaday.com/2016/08/15/ask-...ears-good-for/

Because magnetic gears are not in physical contact friction is negligible so they are favored by clockmakers. Here are some examples...

Bob Mackay - Magnetic Clock

and, for more detail, a build thread of the clock that was featured in Digital Machinist magazine...

http://www.modelenginemaker.com/index.php?topic=3262.0

**mklotz** · Jan 2, 2019, 01:10 PM

Hidden latches with nothing showing on the exterior are fun to design for small boxes such as jewelery or keepsake containers. The "key" is a magnet used to move a steel pin inside the box, thus freeing the lid.

**Redwoods** · Jan 21, 2019, 09:50 AM

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Magnets from hard drives in various uses in the house and garage. I have a stack of drives from which to retrieve the magnets.

Tool board, Metal door hook in garage, Pruning shear holder, Chisels on basement joist, Hammer on garage stud, Chisels on garage wall, Curtain on metal door, Cord keeper on table saw, Clothes hook on basement duct work, Clamps on basement joist.