Coupling Magnetic Fields: Does Orientation Change Strength?

[RichFoster]

TL;DR Summary

Multiple magnets in close proximity. Magnetic fields combine?

Magnetic fields coupling question.

I had to make a small tool holder for my drill press, it hangs on side of press using N52 cylinder magnets.

The holder is 4" long x 3/4 x 3/4" AL bar. With a spacing of 3", two 1/2" holes are bored to accept the 1/2 x 1/2 N52's, which will be epoxied in. I now have two options for inserting the magnets into the AL bar. I can place them in same orientation, N-S and N-S (or S-N S-N, etc), or, one N-S and the other S-N. Question is, does placing them into the AL bar as N-S and S-N make them hold stronger onto steel/iron?

 

[Baluncore]

The relative arrangement of the magnets is important.
Do you want one side of the bar to be magnetic, or both sides of the bar ?
https://en.wikipedia.org/wiki/Halbach_array

Can you please attach a diagram.

 

[RichFoster]

Sure, pic attached. Very simple.
Only one side holds onto the press, the exposed end of the magnets, etc. The bore is only 1/2" deep in a 3/4" AL bar, etc.

But see, I can orient the magnets in same polar direction, or have one flipped. Does having one magnet N and one magnet S attached to iron make the holding force stronger, vs two N's or two S's stuck to the iron??

 

[berkeman]

Summary:: Multiple magnets in close proximity. Magnetic fields combine?

I had to make a small tool holder for my drill press, it hangs on side of press using N52 cylinder magnets.

Sorry, even with the drawing, I'm not understanding what you want to do. Do you just want to stick the Al bar to the side of the Drill Press? Is the Al bar the tool? Or is the Al bar just a mechanical support for the magnets that you will stick other tools to?

 

[RichFoster]

Forget the "tool" part, I just want to stick this 3/4 x 3/4 AL bar to a hunk of flat iron. Two magnets are in the AL bar as the pic shows.

Which orientation of the two magnets creates more holding force of this bar to the iron?

 

[berkeman]

Forget the "tool" part, I just want to stick this 3/4 x 3/4 AL bar to a hunk of flat iron. Two magnets are in the AL bar as the pic shows.

Which orientation of the two magnets creates more holding force of this bar to the iron?

Strongest magnetic force is generated when you have a closed magnetic path. So the strongest would be if you could laminate a steel sheet/bar on the back of the Al bar and have reversed orientation of the two cylindrical magnets. Can that work?

 

[RichFoster]

I could add steel over my AL bar (over the magnets?? you mean on the opposite side?), but that's more work. And... I don't need "more" force, just asking if flipping the polarity of the two (relative to each other) makes them pull to the iron with more force?

As-is in my pic, it's basically just two magnet ends sticking to the iron. If one stuck as S-iron and the other N-iron, 3" apart from one another, that makes it harder to pull a magnet off? Isn't this the same as adding a steel bar over the magnets?

 

[berkeman]

I could add steel over my AL bar (over the magnets?? you mean on the opposite side?), but that's more work. And... I don't need "more" force

Yes, to get the most force from your two cylindrical magnets, you would make the holes in the Al bar go all the way through, and put a somewhat thinner steel bar on the backside. You would then put the 2 magnets in their holes with opposite poles sticking out. When you stick that to your metal Drill Press (or whatever), that forms a closed magnetic path.

But if you don't need that extra sticking force, then it doesn't matter much which way you orient the two magnets 3" apart. The magnetic return paths are mostly in the air for each magnet.

EDIT -- You might still get slightly more pull with the two magnets in the Al bar (but without any steel return backing bar) in opposite orientations, but I think it won't be much more.

I did a Google Images search for images of a cylindrical magnet stuck to a steel surface, and actually found an old PhysicsForums thread!

https://www.physicsforums.com/threads/mounting-fire-smoke-alarms-with-magnets.982023/

 

[RichFoster]

Ahhhh. TY for the link.

Edit (for your edit): I did place them opposite. With the info you provided I can always add a iron backer if needed, although there will still be a ~1/4" gap between magnet end and iron backer plate. These 1/2 x 1/2 N52's are decently strong w/o making the horseshoe.

For clarity, this AL bar has various threadings & holes in it so I can attach other tool items.

TY for the help.

 

[Baluncore]

Since the cylinders are simple bar magnets, you could drill the bar at the edge from the side. Then the cylinders would stick on their side to the iron which would better close the magnetic field. You can test that without the aluminium, just stick a cylinder on end or on side and compare.

Alternatively, drill the hole over-size so you can mount the cylinder magnet in a steel sleeve with clearance at one end only. That would make a coaxial circular pole with a opposite pole at the centre.

Take a look at welding clamp magnets to see how the magnetic circuit is closed.