De-Magnatizing digital callipers

Yes, they are sintered in a large block and sliced with a diamond saw.

I thought that was the arrangement of the magnets from your picture. That will give a magnetic field in the Magnetise slot that is zero in the centre and opposite directions at each edge. So as the screwdriver is drawn through it will be magnetised first in one direction and then in the other. You will end up with a south pole at the tip.

Now the field in the other slot will be similar but weaker so the effect will still be to magnetise the screwdriver but weaker. Perhaps if you pass it through as close as possible to the magnet and then again at the opposite side of the slot the effect will be similar to a diminishing alternating field which may reduce the residual magnetism.

I still prefer my solution.

Russell.

Halbach array

Success!

I took one magnet of a type similar to Joe's and waved it back and forth (lontitudally) over a magnetised screwdriver keeping a small gap with a piece of plastic. The result: the screwdriver was partially, but not fully, demagnetised.

Repeated the same process but gradually increasing the distance between the magnet and the screwdriver and it was de-magnetised (almost) fully.

So, the key to using these devices is to repeat the pass through at gradually increasing distance. I guess that's what the steps seen on some of them are for. Not much use for the OP's digital calipers though!

Halbach array -- interesting, it might work better.

Russell.

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Thanks for checking, Joe

Apologies for the delay in responding; We've only just returned from a day-out.

... Looks like the mystery is solved.

MichaelG.

Hi all,
I picked up a degaussing wand that is used for fixing CRT in arcade machines .
Cost $16au on EBAY + a couple of bucks delivery ,I thought for that price i would give it a go !
Plugged it into the mains gave the calipers a wave over it then slowely moved them away before turning off and they are now de-magnetised .

Gave a magnetised screwdriver a go with one of those cheap magnetising/de- magnetising tools as described in this post but it would not work so i gave it a hit with the degaussing wand - instantly de magnetised , then run it thru the remagnetizing side of the magnetising tool and it was re magnetised .
Still have plans to make a bigger unit though as i don't know if this wand would be big enough to do a vise or the like .

Now i want one of those magnetic wand thingies to pick up the long curly swarf from my machines before i vacuum but they want $70 for one !
Does anyone have an idea of how to make one ?

Ian

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It's constructed rather like a closed-off bicycle pump

with a button magnet where the leather washer would be.

MichaelG.

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Edit:  Turns out that Eclipse sells one.

Edit:  and there is a thread here with a brilliant post from John S.

Edited By Michael Gilligan on 11/07/2013 07:54:17

Edited By Michael Gilligan on 11/07/2013 08:00:36

Mike gave me a small one which he made, as shown here , which is very useful for picking chips off machinery. There's no reason why a much larger version couldn't be made for the floor.

Andy

Thanks Michael and Andy ,
Something so simple but why so expensive !
Looks like a simple project for the weekend !

Ian.

Just for any Australian or New Zealand residents interested in making a swarf wand as described in MEW 172 or was it 174? anyhow you can get the required magnets fron AMF MAGNETICS in Botany Australia .
No connection etc but a very east transaction over the phone and you can buy online etc .
I got 10 of 12.5 mm OD countersunk magnets rated for 12 kg pull for around $18 AU - (prices may change in the future ) you could of course buy only one magnet at around $2.50 + GST .

Not sure why a could not remember this Article in MEW ?
I suppose that at the time i was not using a Vacuum cleaner in the Workshop and dismissed it as something i would never need !
Oh how things can change in such a short time !

Ian

I made a "swarf stick" from scrap,(except the magnet ). 3/4" copper water pipe OK 20mm, solder copper disc one end. Works great and good for finding dropped bits.

On the subject of picking stuff up, I have my late mother's "reacher" - this sort of thing - in the shop, and find it very useful for recovering items which have fallen behind machines or under benches. Mine has a magnet on the end; fairly weak, but can be used to draw a small item into a better position for grabbing.

It also saves a lot of bending to pick up all the twigs my ash trees shed before I mow the lawns.

A bit off topic, but we seem to have picked the bones out of demagnetisers.

Andy

For magnets in NZ , Magnets New Zealand Ltd. [email protected]

Web site www.magnets.co.nz

I have had good service from this place. I made my fist order to the company, and just as I sent the E-mail, a TV program came on about the amazing stuff they are making in the magnetic equipment line in their Auckland factory. Ian S C

A swarf picker up device is simply a magnet in a plastic bag and then cart the swarf to the bin and remove the magnet from the plastic bag!

Simples.

Clive

I had a play around in the workshop today and one job was to mill some keyway slots on the mill , i chose the x2 as they were only 4mm and it has a higher speed capabillity than the HM46.
I had recently purchased a screwless vise off ebay and it was cheap but acceptable for what i want to do but when i sat a parrallel on the vice it immediately stuck to the fixed jaw , so the vise was magnetic or at least this jaw was .
Out with the degaussing wand i purchased to give it a go and i was not expecting a result as it was still clamped to the table but i had to give it a go.
I had to try without removing the vise as i had only trammed it a few days earlier so i had nothing to lose .
After 3 passes with this cheapo wand it was de magnetised and i couldn't believe my luck !

Thanks Ian sc for the links as it gives us southern hemispherians  an option or two !
 

Ian

Edited By SLOTDRILLER on 13/07/2013 11:38:31