Non-electrical demagnetiser (demagnetiser)

[sophiecentaur]

I need something to demagnetise my workshop tools. Recently, I've been turning and milling steel parts and everything is collecting a lot of swarf (chips). Somehow, it's all getting magnetised at a ridiculous rate and the stickiness is beating my vacuum cleaner. I was looking into the idea of buying a 'proper' degaussing machine but they tend to be pricey. I see an alternative that's advertised everywhere. It obviously has an array of permanent magnets inside and they must be arranged so that moving a hand tool through it will alternate polarity of field, getting progressively weaker. This sort of thing is now possible, since really powerful permanent magnets became so cheap.
But it stuck me that the best you can hope to do would be to reduce the residual magnetisation in the tool to the step size in the graduations of field strength. Has anyone ever used one and was it any good?
Unless it's good enough to stop my swarf-pickup problem I may have to try a DIY solution with an old transformer and a hacksaw(?*****)

Image from Farnell Website

 

[Vanadium 50]

Sure, it's not perfect. Neither is one using electromagnets. How good does it have to be? And is it any worse than an electric one?

Further, it costs $1.08. How much effort is it worth sweating it?

 

[sophiecentaur]

How good does it have to be?

Good question. Some of the swarf is tiny dust particles and they will stick to virtually anything. Also, some tools are actually quite massive (500g). Trouble is that vibration happens and also there are a number of magnetic bases (clamps for Dial Indicator Gauge for instance). That's a relatively modern phenomenon. To use an electromagnet degausser you bring the object close to the machine and move it away slowly. That way, the field alternates many times during the operation and the remaining field can be very low. It's a technique that was used to degauss old colour CRTs and tape heads. Also, for the old tick tock watches (like the one I wear). The convergence and colour purity on a CRT can be very sensitive to magnetic field - like when you turn the set to face a different direction in the Earth's field. Take one of this modern jobs near an old CRT and you would probably have some real trouble.
The degaussing tables that you can buy use 10A from the mains supply and, natch, get pretty hot pretty quickly. I could order one from China for about 50GBP and I wouldn't be sure of what to expect. A pukka one is about 200GBP minimum.
I may have to bite the bullet and DIY a scrap tranny.

 

[Baluncore]

I use those two hole de/magnetisers successfully for hand tools that need treatment.
You need to experiment with the technique, until you can realize the possibilities.

The two hole de/magnetisers usually stay in my toolboxes. I get them from people who cannot work out how to use them.

If you can't compete with magnetism, use it. Magnetism in HSS tooling can be overcome by strategically placed stronger PMs. That gathers the magnetic swarf in convenient clumps for disposal. The work piece or the drill then rotates in the field while cutting. Magnetron magnets will catch most swarf when milling or peck drilling small holes in steel. Which reminds me, I should be in the workshop now.

 

[sophiecentaur]

If you can't compete with magnetism, use it

And that's the problem - I use it much more than I would have done a few years ago - it's that eBay site that gives me magnets for every purpose. It's not bad enough to make me go for the electric solution so I will have to buy a cheap one and see how well I can do with it. But what to do with the saddle of my lathe, I can't imagine; that thing gets covered with a light coating of swarf and it's so handy to stick a dial gauge on it with the magnet.

The DIY Electrical solution is something for later, perhaps. It's interesting that no one has told me "Yes, I bought one for 50GBP (/ wound one) and it keeps my machine tools perfect." PF is full of have-a-go ers.

 

[Baluncore]

It's not bad enough to make me go for the electric solution so I will have to buy a cheap one and see how well I can do with it.

You could make a degaussing wand from a stack of circular magnets (with holes) and iron washers. Alternate the magnets NS, and washers w, along a non-magnetic bolt in the sequence w,NS,w,SN w,NS,w,SN,w. That way the washers become alternating N and S poles.
To keep it clean, put it in a PVC tube, pot it in epoxy, or heat-shrink tube.
1. To degauss, sweep a surface (axially) as you lift it slowly away.
2. Meanwhile, use it to catch or collect swarf.
3. Find dropped items by rolling it across a surface.

 

[Vanadium 50]

You could make a degaussing wand from a stack of circular magnets (with holes) and iron washers.

Or you could buy the one showed for $1.08.

I think the starting point is requirements. It sounds like the biggest problem with the gadget shown might be its size.

 

[Baluncore]

It sounds like the biggest problem with the gadget shown might be its size.

The problem is how to degauss a 100 x 200 mm steel reference surface.

 

[sophiecentaur]

The problem is how to degauss a 100 x 200 mm steel reference surface.

This is the problem and 100X200 mm would be a suitable minimum for most requirements. What you can buy is perfectly suited to screwdrivers and small spanners. You can actually get them in the holes!
I'm fighting the results of Neodymium magnets. They are a seriously two edged sword. Machining steel involves vibration (especially on my little lathe) and local heating, both of which we learned about in our early school physics.
I was staggered when I learned about magnetic chucks, which hold workpieces tight enough for milling. I would think that nay piece of steel that had been held and worked that way would have an embarrassing level of magnetisation. Suppliers don't seem to make a big thing of selling degaussing tables. ~surprising.

 

[Baluncore]

Why not use a physically rotating degausser that has two or more alternating poles. You could mount it in a cordless drill. As you sweep a surface, the alternating field falls of as you gradually move away. You could make it from a few pairs of neodymium magnets.

 

[sophiecentaur]

a physically rotating degausser

That's not a bad idea. I think it may be a bit safer to hold it in a bench press drill and have some way of holding the workpiece as the device is held down on it and then lifted off in a controlled way. A few quid spent on magnets could be good value. Meanwhile I have ordered a small one with two holes in and will see how limited it actually is.

 

[sophiecentaur]

I found this link. The demagnetiser in the link looks very straightforward and could be applied to a large object by moving it around. I shall definitely order some magnets and make one.