Cutting Alnico Magnets?

[ken]

Now, does anyone know where to get a halfway decent thin aluminum oxide cutting wheel? I looked a Harbor Freight, and what they had didn't look very good. I'm looking for a 6" or 7" wheel with a 5/8" arbor hole.

I never thought diamond wheels would be easier to find than aluminum oxide ones.

Thank you,
Ken

[EtLa]

I will also demagnetize them and remagnetize them. I use a large tool demagnetizer to demagnetize and Neo Bars to remagnetize.

about remagnetizing with neo bar i ask a magnet company about that a long time ago and here was his answer.
did someone notice a difference with a gaussmeter?

As for the magnetizing Alnico magnets wit Rare Earth magnets you could do it using the size that you outlined 3" x 1/2" x 1/2". Only thing that I would like to point out doing this way you do not SATURATE those magnets using this method of magnetizing. Even using two of Rare Earth magnets and placing Alnico magnet in between you still do not get the full saturation in same way as using DC Discharge magnetizer.

[SK66]

I notice an initial INCREASE in gauss after remagnetizing or reversing polarity. I think this is probabl;y due to the fact that I start with a charged magnet and it doesn't fully demagnetize. I will also say that I have seen reference to magnetizing using other magnets on magnet manufacturers sites.

[EtLa]

I notice an initial INCREASE in gauss after remagnetizing or reversing polarity. I think this is probabl;y due to the fact that I start with a charged magnet and it doesn't fully demagnetize. I will also say that I have seen reference to magnetizing using other magnets on magnet manufacturers sites.

thx sk66
very interresting, I think that I will build myself a gaussmeter (with the new A1323LUA Allegro hall-effect) and make some test... also I remember that I used to have a tape demagnetizer in the 70's where did i put that thing?

[Possum]

nah........

in my experience when you charge an alnico magnet it always charges up high and quickly stabilizes at a lower level, has nothing to do with switching poles or what charge it had before, it just can't hold that higher charge and dissipates it. You can also degauss alnico down to about half its charge and over a week or two because the charge is so weak the magnet will not be able to maintain its charge and will degauss almost all the way.......fun with Mr. Science.....

[ken]

I had a huge demagnetizer once myself, I am going to look in my storage area and see if I can find it. I'm not really sure, but I think the neo magnets will charge up but don't really saturate a magnet like a 'DC' magnetizer because the DC discharge is a huge all at once pulse of power, which 'shocks' the magnet into saturating.


I used to have a 1950's Hammond organ years ago, I remember reading on the back of it that if you wanted to test one of the pickups in it, you were not supposed to use an ohmmeter. This is because supposedly the current flowing through the pickup coil from the meter would demag the magnet. I'm thinking about passing a low DC voltage thru a pickup winding and see if this really works.

Ken
ohmwiz@yahoo.com

[SK66]

Actually, this makes sense. Passing current thru a coil will create an electromagnetic field, getting the field's polarity correct will be key in "charging/discharging" an alnico slug within the field. I would be very surprised if an ohm meter has enough current to do anything to alnico.

[David Schwab]

Bartolini used to advise not to use older style analog VOM's... they said it might damage the coil. The newer digital VOM's are a lot safer.

[ken]

I have a couple of real 'old school' VOM's here, one has a 221/2 volt battery
for ohm readings. I imagine that may have enough oomph in it to demag a coil wrapped magnet.

I got an idea for an electric 'dunstunner' from my old organ - I have a big bulk eraser, a variac, and a big rectifier bridge. Maybe if I feed the bulk eraser with known quantities of DC, I can demag magnets to spec. Any ideas?

Ken

[psychotech]

Hello...

Have any of you tried to cut Alnico magnets?

I have a pile of long stick magnets I got from somewhere, if I can cut them down I can use them.

Ken

Well if you have not tried the new little dremel Diamond Cutting Wheels you are in for a surprise. I was able to cut 1.2mm off of a 2.5" AlNiCo V Humbucker type bar magnet with a cheapy dremel on high speed with one wheel. The wheel is 20.1 mm in diameter when new. After cutting one magnet taking 5 minutes in three attempts, letting the magnet cool and feeling it for temperature and it was surprisingly cool and did not produce excessive heat. The cutting wheel SHOWED NO WEAR, only slightly polished on the edge but still 20.1 mm. I am amazed that this solution for this problem has not been used and known of before this.

Regards,
TommyTone
tomsguitartone.com

[black_labb]

i think i'll have to cut some magnets then, as i have 5 10mm diameter by 30mm magnets. 10 10mm diameter by 14mm magnets would be more useful.

[Possum]

...

I got a cheap tile cutting saw at Home Depot and it works very well for cutting alnico, no dust and suprisingly fast cutting. You have to figure out some good way to hold the magnet square to the cutting blade but other than that it works well for cheap. But cutting alnico is a pain in the butt so I never use it and don't design around having to cut alnico to size...