how do switchable magnets work?

[kd0afk]

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

 

[kd0afk]

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.

 

[kd0afk]

Will iron work better than steel for the pole pieces?

 

[Rivergypsy]

Definitely

 

[kd0afk]

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.

 

[Rivergypsy]

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...

 

[kd0afk]

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.

 

[BaronJ]

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...

 

[kd0afk]

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...

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

 

[BaronJ]

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

 

[kd0afk]

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

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.

 

[BaronJ]

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.