# how do switchable magnets work?



## kd0afk (Dec 18, 2013)

I did a little research on the subject but still don't understand. The info I could find says that they have two magnets inside a horseshoe bit o took one apart and it was a cylindrical magnet in a cylinder.  Nothing like the descriptions. And the magnet was an alinco magnet. I would like to try and make my own magnetic bases but with stronger magnets. 
Any help on this one?


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## GailInNM (Dec 18, 2013)

Do a Google search on these and all is revealed.
patent 4251791
patent 4329673
Gail in NM


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## kd0afk (Dec 18, 2013)

GailInNM said:


> Do a Google search on these and all is revealed.
> patent 4251791
> patent 4329673
> Gail in NM



Yeah I saw those but when I took mine apart the housing isn't magnetic. I also saw a different design that uses two disk shaped magnets in a horseshoe. It also doesn't explain starretts design. The starrett bases use a push button not a turning motion.


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## kd0afk (Dec 18, 2013)

I changed my search parameters and found out more. It looks like there are three different types. One like mine which is a diametrically magnetized alinco cylinder housed in a block that is aluminum sandwiched between iron. The second is two disk magnets where one is fixed and one rotates and I think those are in a magnetic housing, I'm not sure. The third is the starrett push button style. I can't find any info on it but I think it's more like a magnetic vise with thin magnets alternating and spacers.
Maybe I'll just buy my bases. I can get the parts I need but it's cost prohibitive and I will most likely need a mill to make them. 
Oh well.


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## purpleknif (Dec 19, 2013)

If you soak the magnets in liquid nitrogen they get WAY stronger. Just be sure to bring them back up to room temperature slowly. I use a "Little Playmate" 6 pack cooler. Let them soak until they quit boiling then just let the nitro boil off.


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## kd0afk (Dec 19, 2013)

There's nothing wrong with using just a regular magnet instead of a switchable one is there? Switchable magnets are very convenient but I can do ok with just a magnet.


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## kd0afk (Dec 19, 2013)

purpleknif said:


> If you soak the magnets in liquid nitrogen they get WAY stronger. Just be sure to bring them back up to room temperature slowly. I use a "Little Playmate" 6 pack cooler. Let them soak until they quit boiling then just let the nitro boil off.


I live in a town that has four hardware stores to serve 6800 people and none of them even have a full set of letter drills, I doubt that I'll find liquid nitrogen.  And if I do how would I transport it. They don't even sell dry ice around here.
Great tip but I won't be able to utilize it. I have heard that cryogenic treatments of metals make them perform better like razors and musical brass instruments.


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## purpleknif (Dec 20, 2013)

Actually, you get liquid nitrogen at a welders supply. Where I get mine its free if I go on a Saturday ever since I took them McDonalds gift cards. You can transport it in a thermos bottle if its vented. Without a vent you'll have a BOMB
 I used to treat R/C race car motors 5 at a time. Put enough juice in to cover them, close the cooler, get home and open it up, let it boil off & done.
  Mags got way stronger giving more torque & rpm.


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## kd0afk (Dec 20, 2013)

Welders supply? You mean ace hardware?


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## Rivergypsy (Dec 20, 2013)

Hi,

I've designed a few bases like this lately, and you want diametrically magnetised rod magnets between two pole pieces, so you can rotate the poles in an out of alignment. If you want a diagram then pm me and I'll send it on Monday.

Easy job to do, and you can do two magnets in a little trick for serious grunt.

Dave


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## purpleknif (Dec 22, 2013)

kd0afk said:


> Welders supply? You mean ace hardware?



 No, a welding supply place where they sell welding gasses. Oxygen, acetylene, argon and such.


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## kd0afk (Dec 22, 2013)

Yeah ace hardware. That's it for this town. There's no welders supply place here. Gotta go 50 miles to the next town for that and I don't have a car.


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## kd0afk (Dec 26, 2013)

OK,  upon closer inspection with a magnet and a file I found that the body is made of what appears to be aluminum sandwiched with steel. Did they braze them together? Could I bolt the layers together? I found diametrically magnetized magnets with a through hole and holds 78lbs. It's 1"x1.5" long with a good sized bore. I betcha I can make one.
Would brass separating the poles work?


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## kd0afk (Dec 26, 2013)

Sorry


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## kd0afk (Dec 26, 2013)

Could I use stainless steel as the center layer and braze the layers together?


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## Rivergypsy (Dec 27, 2013)

Hi,
Brass should be fine, and I'd assume the layers are bonded with a structural adhesive, but I'd be careful of stainless unless you're 100% it's not magnetic - too many of them are.
If you've got 78lb on one, do try two - it's an education on how two fields multiply ;0)

Dave


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## kd0afk (Dec 27, 2013)

Rivergypsy said:


> Hi,
> Brass should be fine, and I'd assume the layers are bonded with a structural adhesive, but I'd be careful of stainless unless you're 100% it's not magnetic - too many of them are.
> If you've got 78lb on one, do try two - it's an education on how two fields multiply ;0)
> 
> Dave



Are you talking about side by side or end to end?
And brazing should work with steel and brass, right?


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## Wizard69 (Dec 27, 2013)

One source of magnets that are really powerful is disk drives.  You have to disassemble the drive to get to the magnets but on the other hand you gain a nice piece of castable aluminum.  If there is a local guy doing PC repairs you might be able to score broken drives cheap or even free.  

On approach that might work for you is a cam release magnetic stand.   Here a lever and cam arrangement is used to pry the magnet assembly off the piece you are stick to.   The problem is the magnets never really turn off, you just force them to break free. Such magnetic arrangements are probably best for semi permanent installations such as lamp assemblies, lube nozzle stands or fan assemblies.


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## Rivergypsy (Dec 27, 2013)

For switchable you really need rod magnets, whereas disc drives have some odd shapes. I agree though that the neodymium magnets have some serious grunt.

For two, did you get the emailed pic? You want side by side in NSSN or SNNS ;0)


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## kd0afk (Dec 27, 2013)

Rivergypsy said:


> For switchable you really need rod magnets, whereas disc drives have some odd shapes. I agree though that the neodymium magnets have some serious grunt.
> 
> For two, did you get the emailed pic? You want side by side in NSSN or SNNS ;0)



I got the pics. Maybe when I get into the advanced class I'll tackle dual mags but for now it's going to be a single neo in a steel and brass case.


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## kd0afk (Dec 27, 2013)

Wizard69 said:


> One source of magnets that are really powerful is disk drives.  You have to disassemble the drive to get to the magnets but on the other hand you gain a nice piece of castable aluminum.  If there is a local guy doing PC repairs you might be able to score broken drives cheap or even free.
> 
> On approach that might work for you is a cam release magnetic stand.   Here a lever and cam arrangement is used to pry the magnet assembly off the piece you are stick to.   The problem is the magnets never really turn off, you just force them to break free. Such magnetic arrangements are probably best for semi permanent installations such as lamp assemblies, lube nozzle stands or fan assemblies.



I'll get this in mind for future projects, thanks


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## kd0afk (Dec 27, 2013)

Rivergypsy said:


> Hi,
> Brass should be fine, and I'd assume the layers are bonded with a structural adhesive, but I'd be careful of stainless unless you're 100% it's not magnetic - too many of them are.
> If you've got 78lb on one, do try two - it's an education on how two fields multiply ;0)
> 
> Dave



I was thinking more on the lines of pinning the layers with brass pins and using silver solder. Should hold up well.


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## kd0afk (Dec 28, 2013)

Will iron work better than steel for the pole pieces?


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## Rivergypsy (Dec 29, 2013)

Definitely


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## kd0afk (Dec 30, 2013)

I emailed K&J magnets and they said that since I can't explosive weld aluminum to steel, the spacer between the pole pieces can be made of brass or any of the 300 series of stainless steel. 
So how difficult is it to braze stainless steel to iron? I've never brazed metal before.


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## Rivergypsy (Dec 31, 2013)

I dont know to be honest, as some 300 series can be slightly magnetic. I'd give serious thought to a structural adhesive or a non-mag fastener such as brass bolts...


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## kd0afk (Dec 31, 2013)

I just passed on what they said about the stainless. I plan on using brass spacers with brass pins holding it together and silver soldering the whole thing.


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## BaronJ (Jan 8, 2014)

kd0afk said:


> I just passed on what they said about the stainless. I plan on using brass spacers with brass pins holding it together and silver soldering the whole thing.



You realise that the heat will reduce the magnets strength !

I would stick with super glue since its nice and thin.  The other issue you might find is that the magnets shatter if you try to drill them.  I've dozens of magnets salvaged from old HDD.  Most are quite fragile and will shatter if you drop them any distance onto a hard surface.

With regard to a magnetic vice.  I made a small one using aluminium plates 4mm thick, super glued together and coated with JB weld.  After the JB had hardened I fly cut the surfaces and sides.  Mine ended up about 1" thick and 2.5" wide by four inches long.  Worked great...  Except that you couldn't get the bloody thing off the mill table.  I ended up using a G clamp to get it off.  Then it stuck to the G clamp.  I threw it in the swarf bin after that.  And since the bin was made from tin plate and all the swarf stuck to it, it all went to the scrap dump.

So now you know...


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## kd0afk (Jan 8, 2014)

BaronJ said:


> You realise that the heat will reduce the magnets strength !
> 
> I would stick with super glue since its nice and thin.  The other issue you might find is that the magnets shatter if you try to drill them.  I've dozens of magnets salvaged from old HDD.  Most are quite fragile and will shatter if you drop them any distance onto a hard surface.
> 
> ...



I won't be drilling or heating the magnet, never intended to. I don't understand the purpose of your post.


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## BaronJ (Jan 8, 2014)

kd0afk said:


> I just passed on what they said about the stainless. I plan on using brass spacers with brass pins holding it together and silver soldering the whole thing.



In this post you refer to silver soldering !  Which requires heat...

You also mention brass spacers !  I used cheap alloy...

Using adhesives for me worked fine.

Unfortunately I don't have any photos or the original magnetic vice that I made.  I simply made a long sandwich of magnet, alloy, magnet, alloy...  The JB weld was used as a filler for all the gaps since the HDD magnets have a kidney shape.
HTH


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## kd0afk (Jan 8, 2014)

BaronJ said:


> In this post you refer to silver soldering !  Which requires heat...
> 
> You also mention brass spacers !  I used cheap alloy...
> 
> ...



The drilling and soldering is for the magnet housing. A drill or flame won't come anywhere near the magnet itself. We're talking about the body of the thing that houses a magnet. I think you are talking about an "always on" style magnet.


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## BaronJ (Jan 8, 2014)

kd0afk said:


> The drilling and soldering is for the magnet housing. A drill or flame won't come anywhere near the magnet itself. We're talking about the body of the thing that houses a magnet. I think you are talking about an "always on" style magnet.



Ahh.  It wasn't clear to me.

Yes I was talking about a magnetic chuck as used to hold work whilst grinding or fly cutting.

You will have to post photos of your work.  If you need some HDD magnets let me know.


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