Magnet Fishing


A few years ago, I salvaged a collection of small but powerful rare earth magnets from old computer hard drives.

They've been sat there (well, actually stuck to a bit of shelving), waiting to be used for something.  OK - let's go Magnet Fishing!


What Is Magnet Fishing

Magnet fishing doesn't actually involve fish at all - it's essentially just treasure hunting for ferrous objects that people might have accidentally dropped, or deliberately thrown, into bodies of water.

There are a couple of very popular public fishing spots near me - I'm going to try them first.  Maybe I'll find something nice, or maybe I'll just help to clean up the river by pulling out a bunch of rusty old junk - either way, it's good.

Making My Magnet Fishing Rig



I took three matching pairs of magnets from my collection. The magnets themselves were affixed to crescent-shaped metal base plates that already had mounting holes, but the holes were a little on the small side - I wanted to put a stronger M6 bolt through them, so I had to drill them out.

I made a quick and dirty jig to place them on while drilling them - it's just two bits of wood and a nail, but it works OK - the wood block stops the workpiece from spinning if the drill happens to jam in it, and the nail prevents ribbons of razor sharp swarf from whipping around and slicing my beautiful hands.



It worked just fine - and the nail was a very sensible idea.  The metal drilled very nicely and my magnets were now ready to affix to something.



As a baseplate for my magnets, I decided to use a couple of the recycled HDPE plastic hexagons that I made when I was attempting to make a recycled plastic boat.

The plastic boat project was a failure, but I'm glad I kept these pieces - I knew they'd come in handy eventually.

I marked out the holes and drilled the pieces together.



Then I bolted the magnet plates through both pieces of plastic and secured the other side with a washer and nylon locking nut.

This wasn't easy.  The bolt, the nut, the washer, the screwdriver and the spanner all kept jumping across to stick to the magnet, but I got there in the end.



Next, I needed some way to attach the whole thing to a rope, so I drilled a couple of bigger holes and fixed in a thick, double-ended curved bolt (part of a car exhaust mounting, I think) - I picked it up on the side of the road a long time ago and threw it in my odds box for some future use.

At this point, with all six magnets in place, the thing needs some careful handling - I daren't expose it to any flat metal surfaces - it would stick very hard indeed and would be difficult to remove.



And there we are - the magnet fishing accessory is complete.

In case you're wondering - the metal hoop is deliberately off-centre - this is so that if the magnet should get stuck to something too large or otherwise immovable, pulling on the rope should tend to detach the device at one side first, rather than all at once.

All that remains is to securely attach a length of strong rope, then go off and dangle it in the water to see what I can find - I'll update this page with my results soon...

What Might I find?

Well, proper treasure is probably out of the question, unless it happens to be in a steel box, but there are probably some things worth finding such as tools and knives.  I imagine I'll find a fish hook or two as well, so I shan't attempt anything without the gloves.

Magnet Safety

Rare Earth magnets such as these are very powerful and require careful handling - any of the following bad things could happen:

If you allow two magnets to attract each other in an uncontrolled fashion, they can easily pinch your flesh and cause bruising or blood blisters, or they may shatter into sharp pieces which can cause eye or skin injury.

If you were to swallow one (or worse, two) strong magnets, they can pinch together and perforate your gut, which can be fatal.

If you allow them anywhere near magnetic media such as the magnetic strip on a credit card (or magnetic computer disks or tapes) they will destroy the information on the media.

They will jump to, and aggressively stick to pretty nearly anything made of iron or steel, and can damage the surface of such items.





I attached a piece of strong nylon rope to the metal hoop - I decided to double the rope and attach it with two half hitches, so there was no chance of it coming undone.

Then I went off to the last non-tidal bit of the river Itchen, at Wood Mill, near Southampton.



Grasping the rope securely, I dropped my magnet device into the water, then dragged it along.

I figured the best place to trawl for items should be near the edge.  Maybe I got this wrong though - it could be that anyone who dropped anything there was able to retrieve it easily.

It wasn't very long though, before I caught something...



The first catch was the pull-tab lid of a tin of Spam (presumably the contents of the tin were either bait, or a snack for someone fishing here).

So I carried on...



Next, I got a metal top from a bottle of Newcastle Brown Ale and a random unrecognisable chunk of rusty metal.

Such treasures!  I could hardly contain my excitement!

The Day's Haul

The totality of the day's catch comprised: A rod rest, a hair grip, a piece of wire that might have been part of a fishing weight, a bottle top and a chunk of rust.

I did also gather numerous small flakes of rust - which I assume to have fallen off the metal piling that edges this section of river.

In all, a slightly disappointing collection of junk, all of which I threw away when I found a bin.



Maybe next time I'll find something a bit more interesting or useful.