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Which magnet would I need?

Which magnet would I need?

Which magnet would I need?

(OP)
Hello everyone, I’m designing something that will rotate and it needs to grab onto ferrous material that it rolls over. (Picture a typical rolling pin who’s function is to gather iron filings.). What shape magnet would one use to achieve this idea? The magnets would need to be set so that they attract iron onto the surface of a plastic or brass cylindrical “rolling pin”, let’s say about 2” diameter and 14” long.

For further clarification of what I’m after, I would expect the magnets to adhere (be glued) to the inner surface of the plastic, or brass tube. Or, most likely, adhere to the outer surface of a lesser diameter plastic tube that slides inside of the outer tube. When rolled across a table covered in iron filings, the outer surface collects iron filings. It one were to pull out the inner cylinder with the magnets glued to it, the iron filings would fall off of the outer cylinder.

Thanks for your help,
Dudley

RE: Which magnet would I need?

I suspect this could be accomplished relatively cheaply by using small round neodymium magnets, which are available in mass quantities and are relatively high power.

Machine a plastic or aluminum (or whatever) cylinder, and spot drill holes round the perimeter. Glue your magnets in, then sleeve with brass/plastic tube/sheet.

How many magnets and what pattern depends on how much magnetic power you need to pick up whatever it is you're trying to pick up.

RE: Which magnet would I need?

(OP)
You are onto exactly what I need!!! I think you have solved my question! Thanks a million!
Dudley

RE: Which magnet would I need?

http://www.magsy.co.uk/26253-magnetic-rollers
See the animation there.

Trivia: I find magnets interesting, and have removed my fair share from speakers through the years. Well, long ago, when I was young, I was working for a company that did demolition. One of the things that wound up in my truck was a magnetic roller, roughly 14" diameter by 24" long, as I recall. You could stand back from that thing 20', lob a crescent wrench over there and twang! It's stuck. (but could be pulled off, it wasn't THAT powerful.) Anyway, I was planning to open that thing up and remove the magnets, but simply couldn't find any way to open it or disassemble it, and don't know how it was put together. The end caps were cast aluminum, there was about a 2" shaft, but no other bolts or tabs or rings or anything to undo to break into it. Alas.

RE: Which magnet would I need?

(OP)
JStephan: What you describe is sort of similar to what I’m going to build.

RE: Which magnet would I need?

(OP)
Berkshire, Actually the function of what I want to build and how it collects the ferrous metal operates the same basic way as a rolling pin does, sort of, but its actual purpose isn’t specifically for rolling over iron filings.......that’s just the function that it has to be able to do. It’s possibly quite patentable, hence my limitations on the exact function.

At any rate, I went ahead and ordered a slew of those cylindrical neodymium magnets and will do the fabrication as jgKRI suggested. That design is what I had in mind, I just wasn’t sure about which magnet to choose.

Thanks everyone!!

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