# Demagnetizing tools



## Tozguy (Jan 15, 2019)

I have this demagnetizer 
https://www.jensentools.com/general-3601-magnetizer-demagnetizer/p/424-597
that I am trying to use to demagnetize some Allen keys. I follow the instructions but can't get rid of the magnetization. 
It would be interesting to learn how they get magnetized unintentionally so it could be avoided but till then I would like to be able to demagnetize when needed. 
Is this the right tool? Can I expect to remove the magnetization completely using this tool?  
Thanks.


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## kev74 (Jan 15, 2019)

I bought this beast last month and it works well.  It sounds like something out of a Frankenstein movie when its on, but works well enough that a screwdriver or other tool won't pick up chips after I run it over the demagnitizer.

https://www.ebay.com/itm/L-W-Demagnetizer-L-W-Chuck-Co-Bench-Top-Demagnetizer-110-Volt-60-Cycle-A-C/232999642527?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

I haven't seen to many positive comments about the small demagnitizers.


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## David S (Jan 15, 2019)

If you have one of these old transformer based soldering guns kicking around you can make a very effective demag tool.




David


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## projectnut (Jan 15, 2019)

kev74 said:


> I bought this beast last month and it works well.  It sounds like something out of a Frankenstein movie when its on, but works well enough that a screwdriver or other tool won't pick up chips after I run it over the demagnitizer.
> 
> https://www.ebay.com/itm/L-W-Demagnetizer-L-W-Chuck-Co-Bench-Top-Demagnetizer-110-Volt-60-Cycle-A-C/232999642527?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
> 
> I haven't seen to many positive comments about the small demagnitizers.



I also have a L W demagnetizer of the same era.  Rather than the bright yellow finish mine has a crackle enamel finish.  I believe it was built in the late 1940's or early 1950's.  I've had it about 20 years.  It gets used a couple times a year to demagnetize screwdrivers, pliers, wrenches, etc., etc.  On occasion I've even had to demagnetize a lantern post tool holder.  How it ever got magnetized I'll never know, but it only takes a couple passes through the field to demagnetize it.  It's interesting that it's made by the L W chuck company.  I have several L W chucks for one of my lathes, however none has ever needed to be demagnetized.

The key to Demagnetizing a tool is to run it through the magnetic field several times.  By "running through" I mean to pass it over the machine about 3" above the plate.  If you want to magnetize something touch it to the top of the machine for a couple seconds.

If yours is still missing the light bulb I would replace it.  If I remember correctly the cycle time is only a couple minutes or so.  If it's left on too long the transformer will overheat and melt the insulation.

As for the one the OP linked, I noticed it said it was for "small Parts".  I would venture to guess the Allen wrenches have too much mass for the magnetic field of the small permanent magnet to penetrate.


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## Groundhog (Jan 15, 2019)

Tozguy, if you figure out how to get it to work please let me know 'cause I've tried them on and off since I've had my own tools without much luck.


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## Littlebriar (Jan 15, 2019)

David S said:


> If you have one of these old transformer based soldering guns kicking around you can make a very effective demag tool.
> 
> View attachment 284861
> 
> ...


David,
I've got one of those big soldering guns. What gage wire did you use? Is the number of wraps critical?


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## Bob Korves (Jan 15, 2019)

kev74 said:


> I bought this beast last month and it works well.  It sounds like something out of a Frankenstein movie when its on, but works well enough that a screwdriver or other tool won't pick up chips after I run it over the demagnitizer.
> 
> https://www.ebay.com/itm/L-W-Demagnetizer-L-W-Chuck-Co-Bench-Top-Demagnetizer-110-Volt-60-Cycle-A-C/232999642527?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
> 
> I haven't seen to many positive comments about the small demagnitizers.


I have one of those L-W demag boxes.  Got it from Benmychree.  It works great, loud hum like most of the better ones have.  Will take larger work than small ones will.


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## hman (Jan 15, 2019)

kev74:

https://www.ebay.com/itm/L-W-Demagnetizer-L-W-Chuck-Co-Bench-Top-Demagnetizer-110-Volt-60-Cycle-A-C/232999642527?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Wowsers!  Shipping's gonna get ya on this one!

PS -there's a previous thread about tool demagnetizers here:
https://www.hobby-machinist.com/threads/what-do-you-use-to-demagnitize-your-tools.51704/#post-433183

It includes details of a mag/demag I cobbled up from a motor stator.  Later on I found some PTC resistors, which I added to the circuit.  These resistors initially have a low resistance, which rises as the resistor warms up with use.  Great for demagnetizing - the AC magnetic field starts out full strength, then tapers off.  No need to slowly withdraw the object.  Details of the PTC addition are in post #109 at:
https://www.hobby-machinist.com/thr...ntrol-circuit-wanted.57733/page-4#post-489158


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## JimDawson (Jan 15, 2019)

Tozguy said:


> It would be interesting to learn how they get magnetized unintentionally so it could be avoided but till then I would like to be able to demagnetize when needed.



I have no idea how tools become magnetized, but they do.  As far as I know there is no way to avoid it.  Even ships can become magnetized and need to be degaussed.  http://navymuseum.co.nz/degaussing-ships/

The power demagnetizers work the best.  I think mine was made in the '30s or '40s just by the look of it.  Never tried one of the static demagnetizers.


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## benmychree (Jan 15, 2019)

I use the Neutrofier demagnetizing feature on my surface grinder to de mag. tools.  At work years ago, we used a big DC motor field coil plugged into 110V A.C. for the purpose.


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## kev74 (Jan 15, 2019)

hman said:


> kev74:
> 
> https://www.ebay.com/itm/L-W-Demagnetizer-L-W-Chuck-Co-Bench-Top-Demagnetizer-110-Volt-60-Cycle-A-C/232999642527?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
> 
> Wowsers!  Shipping's gonna get ya on this one!


I got it for $40 shipped.  I thought that was pretty good.


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## David S (Jan 15, 2019)

Littlebriar said:


> David,
> I've got one of those big soldering guns. What gage wire did you use? Is the number of wraps critical?



I used insulated 18 awg and 6 turns around an old plastic form.

David


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## darkzero (Jan 15, 2019)

Tozguy said:


> I have this demagnetizer
> https://www.jensentools.com/general-3601-magnetizer-demagnetizer/p/424-597
> that I am trying to use to demagnetize some Allen keys. I follow the instructions but can't get rid of the magnetization.
> It would be interesting to learn how they get magnetized unintentionally so it could be avoided but till then I would like to be able to demagnetize when needed.
> ...



I've got 4 of the older Wiha demagnatizers (older ones were dark green, new ones are mint green) that works well. I use them on screwdrivers & stuff like that. I did have a cheap generic one that looked like the Wihas but it didn't work very good at all so I gave it away.





I also have a unit that I got from Enco for $30. It's an import but it works very well. I've even demagntized my digital calipers with it.


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## bhigdog (Jan 15, 2019)

The solid ones are useless junk! Spring for a plug in unit from Ebay or HF or almost anyone. They are inexpensive, work very well and last a long time.........Bob+


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## RJSakowski (Jan 15, 2019)

Pure iron and low carbon steel generally don't become magnetized.  Unfortunately, the tool steel we use has carbon and is susceptible.  The magnetic domains in steel are normally randomly oriented so the net alignment is zero and the steel is not magnetized.  When a magnet is brought near, the domains align along the magnetic field line produced by the magnet.  (Visualize some iron filings brought near a magnet.  The filings will align themselves in more or less parallel strings going from one pole of the magnet to the other.)

If the magnet is suddenly pulled away from the steel, the domains retain the alignment and the steel is magnetized.  As a youngster, I used to stoke a sewing needle to magnetize it and if it were placed on a cork in a bowl of water, it would become a compass.   Magnetic fields fall off rather quickly as the distance from the magnet increases.  Doubling the distance will reduce the field strength to 1/8th.  

Years ago, magnets were fairly weak.  The rare earth magnets that surround us in our daily live are much stronger.  The act of casually bringing a piece of steel near one of these is sufficient to magnetize the steel. The magnetic fields created by coils of wire carrying current can also magnetize steel if the current is suddenly switched off.  Using the indicator stands with magnetic bases is another good way to unintentionally magnetize steel.

Steel can be demagnetized by placing in an oscillating magnetic field and slowly withdrawing it.  The oscillations can be done by applying an alternating current to a coil of wire.  The strength of the field created is proportional to the current times the number of turns.  This is the method used by many demagnetizers.  Another way is using a rotating magnet.  I had a cassette tape demagnetizer that just used a bar magnet attached to a small motor.  In either case, the magnetized steel is brought into the magnetic field and slowly withdrawn.  

I have repurposed  on of my soldering guns as a demagnetizer.  One interesting point is, since the magnetic field strength is proportional to the current times the number of turns but inversely proportional to the length of the wire, increasing the number of turns didn't increase the magnetic field.  For my 140w. gun, I use about 6" of 10AWG wire for soldering tips.  Resistance halves for every three  AWG wires sizes so a 14" length of 6AWG wire has about the same resistance.  I made adapters for the lugs on my soldering gun and flattened and punched eyes in the end of the wire.  I annealed and bent it into two 2" i.d.  loops.  On the 100 watt setting, I pegged the 300 amp range on the 100 watt position my clamp on ammeter so I am probably close to 500 amps on the 140 watt position.  At two turns, this gives me 1,000 ampere-turns.

To use, I power the soldering gun and slowly pass the magnetized piece through the coils and pull it away from the coils before releasing the trigger.  A single pass is sufficient.


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## Bi11Hudson (Jan 15, 2019)

The type of work I do (especially computers), I find magnetized tools to be a nuisance. Most of my problems are with smaller tools. And very small, for model building. I have a Weller D-550, pictured above, hanging on my bench.

For my stuff, so small, it works with a soldering tip. Using 12 AWG, or even 10 AWG, to make a larger loop should work as needed. I have been using this technique for at least 30 years, maybe longer but I don't remember for sure. It does require withdrawing the tool from the field a couple of times, but compared to a "Demag Tool", the cost is insignificant. The soldering iron is there for soldering anyway. Just an added reason to have it handy..

The transformer in the soldering "gun" is a fairly low duty cycle, not 100% by any means. But having the tool touch the copper is not important, as there's only a volt or two there. Very *high current, low voltage*. Most of the tools I use it onj are small enough to use the soldering tip.

For what it's worth, I also use a Weller 8200 on remote work. 100/140 watt... I use AWG 14 for a soldering tip. It doesn't last near as long as a proper tip, but it's *cheap*. And just as fast to install.

Bill Hudson​


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## Mwmx54 (Jan 15, 2019)

I just pulled an old 110v ac motor I had recently tossed in the trash back out of the trash and removed the insides to make a demagnetizer today. It creates a crazy powerful magnet though and is quite difficult to pull anything through. I found that holding the item in the center of the windings, pushing the button to power it up while at the same time yanking the part out works best. If anyone knows how I could tone down the power of the magnet i am all ears. On the other hand it demagnetizes them perfectly. Not even the finest of steel chips stick to my calipers or files anymore.


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## Bob Korves (Jan 15, 2019)

Mwmx54 said:


> I just pulled an old 110v ac motor I had recently tossed in the trash back out of the trash and removed the insides to make a demagnetizer today. It creates a crazy powerful magnet though and is quite difficult to pull anything through. I found that holding the item in the center of the windings, pushing the button to power it up while at the same time yanking the part out works best. If anyone knows how I could tone down the power of the magnet i am all ears. On the other hand it demagnetizes them perfectly. Not even the finest of steel chips stick to my calipers or files anymore.


Less voltage is about all you can do.  Perhaps a variac or other voltage reducer.


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## Ken from ontario (Jan 16, 2019)

I tried the small type in the OP's post and could not get it to work properly ,  it looked like it only demagnetized smaller screwdrivers and only when it didn't touch the sides/body of the demagnetizer, so I bought a bigger economy size that Will (D-ZERO) posted  and it does what's supposed to do and does it well, magnetized tools are real pain most of the time but it is hard to justify the cost of buying a HD demagnetizer only to use it once in a while , overall I have no regrets having one in my shop ,to me it is money well spent.


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## GrayTech (Jan 16, 2019)

Mwmx54 said:


> I just pulled an old 110v ac motor I had recently tossed in the trash back out of the trash and removed the insides to make a demagnetizer today. It creates a crazy powerful magnet though and is quite difficult to pull anything through. I found that holding the item in the center of the windings, pushing the button to power it up while at the same time yanking the part out works best. If anyone knows how I could tone down the power of the magnet i am all ears. On the other hand it demagnetizes them perfectly. Not even the finest of steel chips stick to my calipers or files anymore.


If magnetic field strength is proportional to current x no of winds, you need to increase voltage with a transformer. Current and voltage are inversely proportional - if you increase voltage you decrease current. 

Sent from my H3123 using Tapatalk


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## David S (Jan 16, 2019)

GrayTech said:


> If magnetic field strength is proportional to current x no of winds, you need to increase voltage with a transformer. Current and voltage are inversely proportional - if you increase voltage you decrease current.
> 
> Sent from my H3123 using Tapatalk



Well not quite in this case.  He wants to decrease the power.  Which means reducing the voltage, with something like a variable transformer, or a series resistor could be added, such as a 120 vac incandescent lamp.

David


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## Mwmx54 (Jan 18, 2019)

Thanks for the ideas, I need to do something as it is very difficult to use as is. It’s one of those things that now that I have it, I don’t know how I managed so long without one.


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## rust rescue (Feb 3, 2019)

Lets not forget the old tried and true shock method. Just smacking the tool or part on a table edge will usually knock the magnetic flux around to do the job. Not suitable for every thing but effective for screwdrivers, wrenches etc. I am going to have to try the soldering iron trick.


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## RJSakowski (Feb 3, 2019)

GrayTech said:


> If magnetic field strength is proportional to current x no of winds, you need to increase voltage with a transformer. Current and voltage are inversely proportional - if you increase voltage you decrease current.
> 
> Sent from my H3123 using Tapatalk


Actually, for a constant resistance/impedance, Ohm's Law prevails;  V = IR.    Voltage will increase with current. 

You are perhaps thinking of an electric motor where doubling the voltage halves the current but that is because to do so, you change the windings from parallel to series.  This quadruples the impedance netting half the current while driving with twice the voltage.


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## Be_Zero_Be (Feb 4, 2019)

There are several very good threads about homemade demagnetizers, here is mine :
Yet Another Demagnetizer


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## agfrvf (Feb 5, 2019)

You can magnitize tools by beating on them or contact with a magnet.


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## diamond (Jun 11, 2020)

Sorry about waking an old post but I just picked up one of these on ebay for $10 (free shipping and showed up in a couple days)  It worked pretty darn well so wanted to share.  My calipers had become magnetized (probably got too close to my mag bases one too many times) and was really annoying when little tiny metal dust bits got stuck to the jaws.

It took a couple times trying and I opened the caliper to max so I could do one of the jaws at a time.   Doing both at the same time didn't work well.  Once I did that, boom, no more magnetism and my calipers are cleanly hitting zero every time now.

I'd prefer making it but I didn't have anything lying around that would work so spending $10 was an easy fix.


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## hman (Jun 12, 2020)

Looks like a very good tool!  Does the magnetic field slowly go down, or do you have to withdraw the tool before releasing the button?


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## Cooter Brown (Jun 12, 2020)

When Richard King came to my shop for the class he got frustrated with the scraping tools getting magnetized, so he bought a demagnitizer for the class  just like this one..... I love it! I use it on just about everything in the shop.....



Thanks Rich.......


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## gonzo (Jun 12, 2020)

I disassembled the transformer from a microwave.  Then applied ac at about 25 volts to the secondary. Passing tools through the rectangular hole demags nicely.


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## Mini Cooper S (Jun 12, 2020)

I used to have a hand held bulk tape eraser from Radio Shack, worked great. Then one of my employees broke it on me, I was bummed. Now my electro magnetic chuck on my surface grinder does the job for me.   

Richard


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## royesses (Jun 12, 2020)

I use a bulk tape eraser also. Plenty on Ebay for $25 or less. Works great.

Roy


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## diamond (Jun 12, 2020)

hman said:


> Looks like a very good tool!  Does the magnetic field slowly go down, or do you have to withdraw the tool before releasing the button?


It’s fixed.  I slowly withdrew.


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