Homemade demagnetizer

Discussion in 'Horological Tools' started by doc_fields, Dec 28, 2006.

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  1. doc_fields

    doc_fields Registered User

    Sep 29, 2004
    1,256
    19
    38
    Male
    Clockmaker/Watchmaker
    Greentop, MO
    Country Flag:
    Region Flag:
    DISCLAIMER: This is only intended as an educational project, and I can in no way be held responsible for anyone's misunderstanding and misinterpretation of the project set forth. Readers should be advised that high voltages can be present, electrocution can be done to the user, and the use of tools can be dangerous to the uninitiated. If you or anyone else attempts to duplicate this project, then you do so at your own risk and peril, and I cannot be held responsible for your actions, injury, death, or understanding of this project.

    Now that the disclaimer has been made for the mentally challenged and litigious out there....................


    In 30 minutes I cannibalized, stripped, and made a homemade demagger, including photographing it. Took longer to post. Anyway, here goes............

    72.jpg


    Here's the fan in a freezer that I am cannibalizing. The picture is sideways because the freezer is in my junk trailer bound for the landfill.

    73.jpg

    Here's the removed motor assembly on the bench.

    74.jpg

    Remove fan blade.........

    75.jpg

    Remove motor from bracket........

    76.jpg

    Remove rotor end cap bolts, then remove rotor caps......

    77.jpg

    78.jpg

    and finally the rotor, leaving field and laminates and wires.

    79.jpg

    Shown here are the wires from the motor (black), and wires from a simple power cord (white). Strip ends......

    80.jpg

    twist fine wires together on each wire......

    81.jpg

    without twisting the two wires together, insert into wirenut cap and twist clockwise, letting the cap twist the wires together. Twisting the two together before placing cap on it would make a poor connection, and the cap could fall off. Do the other two wires the same way.

    82.jpg

    Here's the wires connected from a power cord (white) to the motor (black). Very simple.

    83.jpg

    This picture shows an e-clip stuck to my magnetized screwdriver tip. The next pic shows the screwdriver placed into a smaller hole in the laminate. It is held in place, then the unit is plugged into the wall. The magnetic field can be felt in the handle. Slowly remove the screwdriver in a straight line from the laminate and keep withdrawing in a straight line from the hole, then about a foot away, unplug unit.

    84.jpg

    85.jpg

    86.jpg

    Voila! Screwdriver tip is no longer magnetized, and no longer attracts the e-clip.

    It should be noted here that I used the smaller holes in the laminations to quickly demag the screwdriver. Using the bigger hole takes several passes, but the smaller hole does a faster job. I happen to have a manufactured demagger, from Jules Borel that I use. To magnetize an object, they say to place the object in the hole, in the center, and plug the unit in. Wait a few seconds, while holding the screwdriver steady inside the hole, then unplug, and remove the screwdriver. It should now be magnetized. Sometimes,depending for various reasons, you may have to do it several times. Same for demagging. To demag, once again, place screwdriver fully into hole, plug unit in, then slowly withdraw in a straight line till about a foot away, then unplug unit. Hope this all helps and makes sense....doc

    Post script: I did not use a momentary contact switch in this unit for clarity, so you would not have to always plug and unplug the unit. Be sure to unplug unit from outlet when done so it does not overheat.
     
  2. Dave B

    Dave B Banned

    Jun 7, 2008
    2,389
    0
    0
    Civil Engineer; woodwind musician; clock repairman
    Westminster. MD
    Country Flag:
    #2 Dave B, Mar 15, 2009
    Last edited: Mar 15, 2009
    You can also demagnetize tools like screwdrivers by passing them between the rods of a Weller soldering iron. Just be careful to use a well insulated (electrically) device for holding it, and do not touch either of the posts as you withdraw the tool.
     
  3. Karlo G

    Karlo G Registered User

    Feb 17, 2009
    94
    0
    0
    Watchmaker
    Rheinberg near Duesseldorf germany
    Country Flag:
    Region Flag:
    Hi Doc,

    your demagnetizer is similar my once using some years

    Karlo
     
  4. bangster

    bangster Moderator
    NAWCC Member

    Jan 1, 2005
    19,035
    284
    83
    utah
    Country Flag:
    Region Flag:
    Good instructions. Good post. Useful advice. Thanks, doc. (And thanks, Dave.)

    bangster
     
  5. dutch

    dutch Registered User

    Jan 6, 2003
    507
    0
    0
    Retired
    Oxnard,CA
    Country Flag:
    Region Flag:
    My thanks to you for posting the clear instructions,I think now even I can do it. I have been planning on making one for years and you have given me the boost to do it.
     
  6. Dave B

    Dave B Banned

    Jun 7, 2008
    2,389
    0
    0
    Civil Engineer; woodwind musician; clock repairman
    Westminster. MD
    Country Flag:
    I like Doc's better than using my soldering gun. I'm gonna go dig in the radio/electrical junk box and see what kind of transformers I have lurking around in there.
     
  7. StephanG

    StephanG Registered User

    Jun 24, 2007
    916
    1
    16
    Australia
    Country Flag:
    You can also get some usefull coils from old electrical relay switches or from the water valves used on washing machines and dishwashers.
    The latter are often very easy to take apart as they were (perhaps not now) made to be serviced.
     
  8. doc_fields

    doc_fields Registered User

    Sep 29, 2004
    1,256
    19
    38
    Male
    Clockmaker/Watchmaker
    Greentop, MO
    Country Flag:
    Region Flag:
    Having been an appliance repairman for 25 years, I forgot about the water valve coils on washers. Yes, they would make good ones for sure. Thanks for pointing that out. Also, one little thing I might point out that would be the downside of using them, besides electrocuting yourself if you're not careful. Never, ever leave the screwdriver within the coil for more than a few seconds. Leaving it within the coil without moving it causes the current draw through the coil to skyrocket, and it WILL burn out the coil and/or get extremely hot and possibly cause a fire. Been there, done that!.................doc
     
  9. Scottie-TX

    Scottie-TX Registered User
    Deceased

    Apr 6, 2004
    936
    36
    0
    Retired
    Mesquite, TX
    Country Flag:
    Region Flag:
    GREAT tutorial DOC. I'd only emend the wire splice. I'd make an inline, twisted, solder connection with shrinkwrap. Nice work. Think I'll make me one too!
    . . . . . . and obviously, one could gussy it up with a small non - metallic case, etc.
     
  10. Dave B

    Dave B Banned

    Jun 7, 2008
    2,389
    0
    0
    Civil Engineer; woodwind musician; clock repairman
    Westminster. MD
    Country Flag:
    I think throwing a N.O. pushbutton switch and maybe a Buss fuse into the supply circuit might not be a bad idea, to help guard against accidental overheating.
     
  11. Scottie-TX

    Scottie-TX Registered User
    Deceased

    Apr 6, 2004
    936
    36
    0
    Retired
    Mesquite, TX
    Country Flag:
    Region Flag:
    Well yeah, that and perhaps a pilot lamp on the power line to remind you it's on. Perhaps two more pilots wired to a bimetallic sensor strip. Closed and operating, glows green. If overheating opens the strip, it closes on the second leaf turning on the red light indicating power interruption to coil. Panel meters of course would monitor voltage and current.
    Later perhaps you could add an auto -feed that moves the tool thru the field, reverses and backs the tool out, with of course programmed options of no. of cycles and auto shutoff after selected cycles completed like a copier.
    Hmmmmmm; Lessee; A laser detector that - - - - - - aw ferget it!
     
  12. Mike Phelan

    Mike Phelan Registered User

    Dec 17, 2003
    9,835
    12
    38
    Retired
    West Yorkshire, England
    Country Flag:
    Region Flag:
    Nice one, Doc. I'd agree with soldering the leads instead of using Scruits (I hate those things!).
     
  13. doc_fields

    doc_fields Registered User

    Sep 29, 2004
    1,256
    19
    38
    Male
    Clockmaker/Watchmaker
    Greentop, MO
    Country Flag:
    Region Flag:
    I would also use solder on the joints. This was a quick demo, so no soldering was done as I had another use for the motor...............doc
     
  14. Bill Ward

    Bill Ward Registered User
    NAWCC Member

    Jan 8, 2003
    1,224
    5
    38
    EE (spec. acoustics) now medicine
    USA
    Is that what they're called in England?! LOL!
     
  15. Scottie-TX

    Scottie-TX Registered User
    Deceased

    Apr 6, 2004
    936
    36
    0
    Retired
    Mesquite, TX
    Country Flag:
    Region Flag:
    Hey! Ain't no worser hier: We calls 'em "wire nuts". Go figger.
    For me, a movement that aint worth the time to repair is called a, "scruit".
     
  16. Mike Phelan

    Mike Phelan Registered User

    Dec 17, 2003
    9,835
    12
    38
    Retired
    West Yorkshire, England
    Country Flag:
    Region Flag:
    That was the actual brand name, Bill! I don't know if you can still buy them now, the thought police have probably banned them, as they do with anything useful.
    They should go for Scotchloks instead - inventions of Satan.

    I know that the phrase "Screw it" has slightly a different connotation in USA! ;)
     
  17. harold bain

    harold bain Registered User
    NAWCC Member Deceased

    Nov 4, 2002
    40,850
    138
    63
    Male
    deceased
    Whitby, Ontario, Canada
    Country Flag:
    Region Flag:
    Mike, not sure why you don't like these connectors. I have used thousands of them over the years, and when used properly, they are fine.
     
  18. Mike Phelan

    Mike Phelan Registered User

    Dec 17, 2003
    9,835
    12
    38
    Retired
    West Yorkshire, England
    Country Flag:
    Region Flag:
    Harold
    The problem with Scotchloks is that they cut into the wire by nicking it, especially if the wire gets moved at all; people use them in cars when they fit extras, instead of soldering, and the wire eventually breaks.

    Mr Sod ensures this will happen in the early hours when it's raining! :0
     
  19. harold bain

    harold bain Registered User
    NAWCC Member Deceased

    Nov 4, 2002
    40,850
    138
    63
    Male
    deceased
    Whitby, Ontario, Canada
    Country Flag:
    Region Flag:
    Mike, soldering can be just as bad if care isn't taken to insulate the wire. Electrical tape breaks down, or slips off. Shrink sleeving, though seldom used, is a good alternative.
     
  20. Mike Phelan

    Mike Phelan Registered User

    Dec 17, 2003
    9,835
    12
    38
    Retired
    West Yorkshire, England
    Country Flag:
    Region Flag:
    My thoughts about insulation tape are the same as yours, Harold!
    Heatshrink sleeving rules OK - I always have some in my workshop.

    Loom tape (not sure what you call it there - used in car wiring) with no adhesive is good for long runs, and you can finish off with HS sleeving, but that's a bit OT! ;)
     
  21. R&A

    R&A Registered User

    Oct 21, 2008
    4,106
    81
    48
    Country Flag:
    This is a good idea,I like this.

    H/C
     
  22. Dave B

    Dave B Banned

    Jun 7, 2008
    2,389
    0
    0
    Civil Engineer; woodwind musician; clock repairman
    Westminster. MD
    Country Flag:
    The other day, I accidentally knocked a container full of balance staves off the edge of the workbench. Of course, the durned container flew open, and there I was with 144 of S LaRose's best assorted balance staves all over the floor. After saying a few choice words, I went out to the garage and got my mechanic's magnetic pickup tool, and swewpt them up, depositing them in the canvas tray under the watch bench. I don't own a demagnetizer, but I remembered this thread, so went back to the garage and found a field coil, with two wires conveniently already jury-rigged together. "AHA!" thinks I, "This musta been my grandfather's demagnetizer." A few feet of lampcord later, and a little tape, and I was in business. So then I thought, "Let's make sure this thing works by testing it on a screwdriver." Well - when I put the screwdriver in the coil, it was bouncing around so durned much, that I could hardly hold it still! And then the coil started to get hot, and let the smoke out! So I quickly snatched the wires out of the outlet (I hadn't bothered to put a plug on the other end) and ran it under some cold water. (I figured either it was fried, and therefore no good, or I had caught it soon enough that the water would not make any difference to the coil insulation.) I let it dry out for a couple of days, then wired it through a SOLA constant voltage transformer, with an output of 19 VAC. That works like the proverbial magic charm. So then I decided to make a little stand. Back to the junk bin, and a coupla 4-40 screws, nuts and washers later, here 'tis - not very elegant, but it does the job, and the cord is long enough that I was able to hold it beneath the canvas and demagnetize all the balance staves in one swell foop.

    Why do I think the transformer would probably sell for more than enough on eBay to buy a regular demagnetizer? LOL
     

    Attached Files:

  23. Ansomnia

    Ansomnia Registered User

    Sep 11, 2005
    2,614
    1
    0
    Country Flag:
    Region Flag:
    Dave, that's a funny story! You certainly didn't mull over the idea "very long" and you got the job done. But I gather you also meant this as a tale of caution!


    Michael
     
  24. Dave B

    Dave B Banned

    Jun 7, 2008
    2,389
    0
    0
    Civil Engineer; woodwind musician; clock repairman
    Westminster. MD
    Country Flag:
    Well - a tale of caution, and a hint that sometimes, particularly in the electrical department, things aren't always quite what they seem, and a hint that it pays to read these threads and occasionally, to remember them.

    I wonder what kind of voltage that motor was originally intended to run on? You don't s'pose it was originally a split field 12VDC car wiper motor do you? It sure didn't like being plugged into the wall; I can tell you that! LOL
     
  25. Dave B

    Dave B Banned

    Jun 7, 2008
    2,389
    0
    0
    Civil Engineer; woodwind musician; clock repairman
    Westminster. MD
    Country Flag:
    OOPS!! NOT 4-40 hardware - it is 6-32.
     
  26. Mike Pana

    Mike Pana Registered User
    NAWCC Member

    Jul 26, 2009
    8
    0
    0
    Engineer, Architect Retired
    New York
    Country Flag:
    Region Flag:
    HI Dave,
    I solved my magnetism problems by using a Video Tape (remember those?) de-magnetiser which I found in my junk box. I got it from Radio Shack eons ago. A few swipes in one direction does the trick on all my tools. Never shut it off in the presence of your tool. It can remagnetize it.
    Remember, never throw anything out. You'll never know when you'lll need it.
     
  27. Dave B

    Dave B Banned

    Jun 7, 2008
    2,389
    0
    0
    Civil Engineer; woodwind musician; clock repairman
    Westminster. MD
    Country Flag:
    I have never owned a bulk tape eraser. (but have often wished I did) I considered using my tape head demagnetizer, but figured I'd be at it for the next two weeks, trying to make sure I got every one of those little suckers!
     
  28. Mike Phelan

    Mike Phelan Registered User

    Dec 17, 2003
    9,835
    12
    38
    Retired
    West Yorkshire, England
    Country Flag:
    Region Flag:
    No, it's an AC motor, Dave, as I can see a laminated stator.

    It looks like one from a record player; don't know about yours over there, but some of the old world ones have the stator coils in series with the valve heater supply, so they are across a much lower voltage than 240v mains.

    Even it is is a mains motor, with no rotor in it, it will get hot as it "thinks" it is permanently stalled.

    HTH
     
  29. flynwill

    flynwill Registered User
    NAWCC Member

    Feb 1, 2007
    1,024
    7
    38
    Rolling Hills Estates, CA
    Country Flag:
    Region Flag:
    Actually for watch parts a tape head demagnetizer works great. It what I use.
     
  30. Dave B

    Dave B Banned

    Jun 7, 2008
    2,389
    0
    0
    Civil Engineer; woodwind musician; clock repairman
    Westminster. MD
    Country Flag:
    Well - that makes sense. If it had been in series with a couple of 6L6's and a 35Z3 or some such for making B+, voltage would have been reduced just a bit. :)
     
  31. Timefrank

    Timefrank Registered User
    NAWCC Member

    Mar 26, 2012
    7
    0
    1
    I use a VHS tape eraser. If you turn it on and off with the tool nextto it, it be magnetized. If you move it away while it is on, it will be demagnetized.
     

Share This Page