Demagnetize turning tools

[Randall Mack]

Has anyone tried one of the blue 120v watch demagnetizers sold on ebay to demagnetize tool steel? I have a packard skew that can pick up a general tool angle gauge. I was trying to measure the angle and the gauge stuck on the skew. It is the only tool i have that is magnetized and is irritating with how it clings to iron. I think there are several threads on this topic. I am going to try striking it and if that fails i guess i need to try some form of degaussing coil. I have no idea why this one tool is like this unless it came this way. Any cheap solutions are welcome. Thanks.

[John K Jordan]

Has anyone tried one of the blue 120v watch demagnetizers sold on ebay to demagnetize tool steel?


Randall,

I haven't tried that one, but I know what works for sure since I use one on my tools: a bulk tape demagnetizer. I turn it on and approach then move the tool away before turning it off. Works every time. Mine is maybe 40 years old but I saw some on ebay and one on Amazon.

There is another way to demagnetize things that I used to use on color CRT screens that involves using a strong magnet, oddly enough. What you do is rapidly swing the magnet back and forth as you bring it towards the tool, never stopping, then move it away while you are still swinging. This is actually the method the bulk tape demagnetizer uses, except instead of physical motion it uses alternating current to reverse the magnetic field.

I have NOT tried this on anything but CRT screens and a screwdriver but if you are looking for cheap, it might be worth a try on your skew. Best to repeat it at several angles. It might take several tries. You want to use a strong magnet and get as close as you can before moving away. (Don't cut your knuckles on the sharp edge of the tool! Maybe cover it with a piece of cardboard or thin plastic.) I think I'll try this myself on a turning tool the next time I go to the shop.

My tools don't pick up other tools but they do cause long annoying black trails of steel dust to stick to the edge when sharpening on a CBN wheel on a Tormek (when the wheel is rotating away from the edge.) Tools will get magnetized from the Earth's magnetic field with use even if no magnet is near, but I'll leave it at that since the last time I posted about that someone got upset. They will, of course, get very magnetized if they come in contact with a magnet.

JKJ

[John K Jordan]

What you do is rapidly swing the magnet back and forth as you bring it towards the tool, never stopping, then move it away while you are still swinging..... I think I'll try this myself on a turning tool the next time I go to the shop.


Randall, I just tried the super magnet demagnetizing trick with a skew chisel and it worked fine.

1) First I magnetized a Thompson skew by stroking with a strong super magnet, a 1/2"x1/2"x1/2" cube. It stuck strongly to the tool rest.

2) I used the same magnet to demagnetize. I put the skew flat on a non-feromagnetic surface (a piece of wood - not on a cast iron saw table, etc.) and covered with a thin piece of clear acetate to keep my skin away from the sharp edge,

3) I did the swinging thing while bringing the magnet up nearly in contact with the plastic then moved it away while still swinging.

4) I then flipped the skew over and repeated the process.

After this I could not detect any magnetism in the skew.

I just realized I just picked up the magnet and didn't pay any attention to the orientation of the poles of the magnet. If it doesn't work at first, I would try holding it so the poles were on opposite ends along the line of the motion.

It occurs to me one might devise a motorized demagnetizer by putting two magnets on a disk, one with North outward and the other with South outward, and spin it with an electric drill. Now this makes me want to experiment with this but it will have to wait for a few days.

JKJ

[Randall Mack]

Thanks John. I will give this a try.

[Randall Mack]

Don't laugh. It worked pretty good. If I was doing this again I would use a plywood disk and get the strongest magnets i can find. I put the skew flat on a non metalic surface and spun the 2 magnets in the same plane as the surface with a cordless drill at a slow speed as close as i could get. Slower worked better. I slowly pulled away the magnets while spinning. It is not 100% demagnetized but almost.
339880

[John K Jordan]

Don't laugh. It worked pretty good. If I was doing this again I would use a plywood disk and get the strongest magnets i can find. I put the skew flat on a non metalic surface and spun the 2 magnets in the same plane as the surface with a cordless drill at a slow speed as close as i could get. Slower worked better. I slowly pulled away the magnets while spinning. It is not 100% demagnetized but almost.



Nice! Yeah, the AC demagnetizers are 60 cycles/seconds but my manual swing-arm can't be over 5 cps so I suspect the speed is not as important about other factors. I suspect the two magnets could be closer together but again, I haven't experimented with this, just theorized. Demagetizing a color CRT screen was easy since you do it while the screen is on and can see from the color distortion what effect you are having and can see exactly when you are done!

Did you use the opposite poles on the magnets?

JKJ

[Randall Mack]

Yes the poles are reversed. The magnets are 3/8 diameter x 1/4 length pushed into a 3/8 hole spaced about 5 inches apart. Actually 2 magnets in each end. There was no reason for the distance, just a guess. LOL, I was hoping someone on youtube had done all the work. I messed with it for 30 minutes or more until I was satisfied. I may play with it more if I notice build up of filings on the skew end the next time sharpened. Thanks John for the idea.