Once again, a neodymium magnet came too close to a formerly unmagnetized screwdriver and left its tip magnetized. :( Sharply striking it with a heavy hammer always fails to demagnetize such screwdrivers.
The Jakemy JM-X3 [1] looks promising. Is there a better way? TIA.
Note.
There's demagnetizing coils (AC powered air-core inductors); you can either slowly draw a screwdriver through them and away, to demagnetize, or stick it into the bore and disconnect the AC, to magnetize them. Bulk tape erasers, tape head degaussers, and TV degaussing coil 'wands' all work the same way.
I like the coils better than the permanent-magnet types, because you can demagnetize large objects.
Classic soldering guns work, too.
Yup, the old Weller-style transformer soldering gun, with the loop of heavy copper bar tip that is bolted to two posts that stick out the front of the gun (I'm describing this for the few who may not know this older style). Pass the screwdriver through the loop of the tip, squeeze the trigger and slowly pull the screwdriver through the loop, until it is at least several inches from the gun before releasing the trigger. It only takes about 3 seconds to do it. Works like a CHARM!
Jon
We laugh at wussy little Wellers. Real Men use a Wen 250.
If the thing works @ $7 then I think it's not worth the trouble of winding a coil around the screwdriver, connecting a 4 Ohm resistor in series and hooking it up to your audio amplifier while inputting a sine wave generator's signal while turning the frequency knob from low to high (and maybe the volume from high to low)...
joe
I have several of these: which will both magnetize and demagnetize. They work just fine on screwdrivers. However, for odd shaped objects, that won't pass through the holes, I use an old bulk magnetic tape eraser.
Hint: When done demagnetizing, move the screwdriver away from the tape eraser and then turn off the power to the demagnetizer. If you turn it off while the screwdriver is still in the magnetic field, you run a good chance of re-magnetizing the screwdriver.
More:
Proper degaussing, in the blind, requires a large but gradually reducing AC field.
Employing static fields will be hit or miss, without instrumentation.
RL
Indeed. Works like a charm! Thank you very much Jon for your detailed description of the demag process. And thank you all for taking the time to answer my question.
On a sunny day (Sun, 31 Jan 2016 02:31:07 -0000 (UTC)) it happened Don Kuenz wrote in :
Probably putting it in my induction heater coil would work. Too long and you need to harden the steel again (if it gets red hot).
I like magnetic screwdrivers. so even make them magnetic.
If you have an induction cooker maybe give it a try?
On a sunny day (Sun, 31 Jan 2016 01:11:38 -0500) it happened legg wrote in :
For the old tape erasers and TV shadowmask deagausers you had to circle and move slowly backward.
Dunnit many times.
Or you can leave the screwdriver in the coil and turn down the voltage slowly to zero, if you have a variac. Everyone should have a variac.
If you don't have a coil, you can use an old power transformer with the laminations pulled out, but probably it wouldn't like full mains voltage without the core fitted. This doesn't matter as you can run it at reduced voltage if you have a big variac.
On a sunny day (Mon, 1 Feb 2016 00:27:41 +1100) it happened Chris Jones wrote in :
Big triacs and a diac are much cheaper, also called 'light dimmer' sometimes. YMMV if it does not swich symmetrical you get some DC component.
I have used a 150 W audio amplifier and a step up transformer (mains transformer for audio amp backwards) to make 60.x Hz mains 100 W variable amplitude here with the PC as signal generator (for my cryocooler). We have 50 Hz mains. Tronix is about improvisation.
For a fixed amplitude AC field, the gradual field reduction is achieved by gradually increasing the distance, hence the 'slow' circling and retreat.
RL
Manual SMD handling tools need degausing regularly, or they will shift and cling to components unpredictably - steel being a common terminal and IC carrier core material.
If the parts themselves become magnetized, they'll foul auto-insertion.
RL
On a sunny day (Sun, 31 Jan 2016 12:35:36 -0500) it happened legg wrote in :
Thats is true, OTOH I do everything with a pincet and solder first one side, then the other side:
The ones that can be magnetized I have same mounted with:
peeseebee in mass production is evil^H^H^H^H different.
Unscrew the shaft mount from cheap AC fan motor, the kind with a big coil off to the side and shorted windings producing the rotating field. It does long range degaussing (and gets very hot) if you slice it open to be a 'C' shape.
I always suffer a moment of confusion when someone uses that phrase.. just how well do magic spells actually work?
--sp
Don Kuenz prodded the keyboard with:
Just drag it across the top of the lamination's of an energised transformer.
I use the wiha mag/demag block too. Felt silly buying getting it as first, but you may need to mag or demag a tool in the field.
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